8th assignment session 2024-25

 Annual syllabus 

1. Reproduction in Animals

2. Reaching the age of adolescence

3. Force and pressure 

4. Friction

5. Chemical effects of Electric current

6. Light

7. Combustion and flame 

Assignment 

Lesson 1 ` Crop production and management`

1.What is a crop?

2. What is ploughing and tilling ? State its advantages.

3. State the important steps taken during crop production.

4. Write short note on the terms : 1. storage and 2. harvesting

5. Propagation of ginger is generally done using

(a) Seed     (b) Stem         (c) root     (d) leaf

6.Which activity of the farmer can promote growth of earthworms and microbes in the field ?

7. Name the tool used with a tractor for sowing seeds in a field . what are the advantages of using this tool?

8. During which months do farmers grow mustard in India?

9. What is sowing ?

10. Name the two modern methods of irrigation that help us to use water economically.

11. Why can paddy not be grown in the winter season?

Lesson 2 ` Micro- organisms : friend and foe

1.Give one word answers

(a) The process of conversion of sugar into alcohol   

(b)Disease causing microbes     

(c) A virus that feeds on bacteria     

(d)The first scientist to have discovered microorganism     

(e) The scientist who discovered vaccine for smallpopx     

(f) The scientist who discovered fermentation     

(g) An insect which is a carrier of parasites of malaria     

(h) An insect which carries the dengue virus     

(i) A biological nitrogen fixer   

2. What are microorganism ? Where do they live ?

3. How microbes is used in making of curd and bread ?

4. Explain medicinal use of microorganisms.

5. Write some diseases caused by (a) Bacteria     (b) virus     (c) protozoa

6. What are preservatives ? Name some commonly used preservatives .

7. Explain in detail the process of pasteurisation .

8. What do you mean by carrier of disease ? Name two such carriers and the disease they caused .

9. What do you mean by food preservation ? Write some ways to preserve food.

10. Explain nitrogen cycle in detail.

Lesson 3 Coal and petroleum

Lesson 4 Combustion and flame

Q1 Fill in the blanks :

1. A blue flame on a burner shows _____ combustion .

2. Hottest part of the candle is its ____ zone .

3.Mined coal and petroleum are _____ fuels

4. ______ has the highest calorific value among the fuels.

Q2. MCQs

1. Which of the following is not used as fuels?

(a) LPG    (b) CNG     (c) hydrogen     (d) oxygen

2. Combustion is the process of

(a) Production of explosive sound     (b) Formation of carbon dioxide     

(c) vaporisation of a fuel                 (d) burning of fuel emitting heat

3. The colour of the flame with the highest amount of fuels?

(a) white     (b) yellow     (c) red     (d) blue

4. Which of the following is caused by burning of fuels?

(a) Acid rain         (b) global warming     (c) emissin of carbon monoxide     (d) all of these

Q 3. Answer the following questions

1. What are the requisites of combustion ?

2. Explain different types of fuels and their uses .

3. Write a short note on the calorific value of hydrogen . How Will you differentiate an ideal fuel.(characteristics of good fuel)

4. Define the terms :- ignition temperature , calorific value of the fuel , inflammable substances

lesson 5 Conservation of plants and animals

1. Why do some birds migrate from one place to another ?

2. Name any three (a) bird santuaries     (b) wildlife sanctuaries     (c) national parks in India

3. list some of the natural disasters which are a danger to biodiversity

4. Why do we consider tiger an endangered species ?

5. Why each one of us must plant at least one tree in our lifetime?

6. What are the main causes of extinction of species ?

7. What purpose is served by biosphere reserves?

8. How ecosystem is the self supporting system of an organism?

9. Write a report on project tiger.

10. Define endemic species.

11. Write some ways to save paper.

Lesson 6 Reproduction in Animals

1. Short Answer questions

(a) Creation of new life of its own kind

(b)Animals which lay eggs

(c) Animals which give birth to young ones.

(d) A sperm producing organ

(e) Ova producing organs

(f) Product of fertilization

(g) The organ where fertilization takes place in humans

(h) Fusion of gametes

(i) The organ which holds foetus in females .

2. How does hydra reproduce?

3. Explain in detail the male reproductive organs.

4. Explain in detail the female reproductive organs.

5. Explain the `invitro` technique of fertilization ? Why is it necessary to adopt this method of fertilization ?

6. What is a clone? Write advantages and disadvantages of cloning.

7. Describe post fertilisation stages till the formation of foetus in women.

8. Label the parts of female and male reproductive systems:

Lesson 7 Reaching the age of adolescence

Q1 Very short answer questons

(a) Period ofgrowth from childhood to adult

(b) The first menstrual flow

(c) Stoppage of menstruation

(d) The master endocrine gland

(e) The mineral essential component of thyroxine

(f) The hormone which regulates the maturation of testes.

(g) The hormone produced by ovaries on puberty

(h) The oil secreting gland present in the skin

(i) The protruding growth of larynx in male.

(j) The spoken term used for adolescence

2. How many chances are there in nature that a woman may be a male or a female baby?

3. What is a teenage period in life? Why do we call it teenage?

4. Why doe we call the pituatary gland as master gland ?

Q2. Short Answer Questions

1. What do you mean by the terms menarche and menupause?

2. Why is a diabetic patient advised to take insulin injections?

3. What are the nutritional necessities of adolescence and why?

4. Female foeticide is a crime against humanity .

match the following:

column 1         column II

1. Growth hormones                                             voice box

2.Pituatary gland                                                 thyroxine

3. XX chromosomes                                                male child

4. Adrenal gland                                                     male hormone

5. THYROID gland                                            Adrenaline

6. XY chromosomes                                         female child

7. Pancreas                                                        stoppage of menstruation

8. testosterone                                                 insulin

9. menopause                                                 master gland

10. Adam`s apple                                         pituitary gland

Lesson 8     Force and pressure (Grade8th)

1. It is difficult to cut cloth using a pair of scissors with blunt blades. Explain.

Ans 1 It is difficult to cut cloth using a pair of scissors with blunt blades because blunt blades have more area and due to which applied force produces very less pressure. As we know that pressure is inversely proportional to area of cross-section, so it is difficult to cut cloth from blunt blades.

2.Two women are of the same weight. One wears sandals with pointed heels while the other wears sandals with flat soles. Which one would feel more comfortable while walking on a sandy beach? Give reasons for your answer.

Answer 2. While walking on a sandy surface, one needs the footwears of larger area so that the pressure exerted on the ground is minimum. So, in this case, the woman having the sandals with pointed heels will be less comfortable in walking while the other woman wears sandals with flat soles feels more comfortable while walking on sandy beach.

3. It is much easier to burst an inflated balloon with a needle than by a finger. Explain.

Answer 3. Because needle tip has very less area of cross-section in comparison to that of our finger and we know that pressure exerted by a force is inversely proportional to the area where it has been applied, so pressure exerted will be more by the needle tip than the finger.

4.What do you mean by contact force ? Explain with the help of example. 

Contact forces : Force that arises with the contact of 2 or more objects involved. Examples : Muscular force and Frictional Force

Muscular force is the type of force wherein we use our physical strength to change the state of motion of an object. Eg: Man pushing a car, Bullocks pulling a cart of load, Cycling, Weight Lifting

Frictional Force is a force that acts on all moving objects by the surface which it is in contact with.

The Frictional force is always in the direction opposite to the applied force

5..What do you mean by non contact force ? Explain with the help of example. 

Non-contact forces: Forces that arise without the contact of 2 or more objects involved. Examples: Magnetic Force, Electrostatic Force, Gravitational force

Magnetic Force is a force that attracts certain metal objects (like iron and iron filings) towards a magnet.

Gravitational : it is an attractive force between two massive bodies .

G= (gmM)/r2

Electrostatic force is the force exerted by a charged body on another charged or uncharged body

6. What is meant by atmospheric pressure ? What is the cause of atmospheric pressure?

Atmospheric pressure:- The air all around us also exerts pressure. This is known as Atmospheric Pressure. The value of atmospheric pressure is very high.

Atmospheric pressure is caused by the weight of the air molecules above the Earth's surface, which are pulled downward by the planet's gravitational force.

7.Two objects repel each other. This repulsion could be due to the

(a) frictional force only (b) electrostatic force only

(c) magnetic force only (d) either a magnetic or an electrostatic force

Answer. (d) The reason for repulsions may be either an electrostatic (in case of similar charges) or a magnetic (in case of similar pole_s) force.

8.A brick is kept in three different ways on a table as shown in figure. The pressure exerted by the brick on the table will be

(a) maximum in position A (b) maximum in position C

(c) maximum in position B (d) equal in all cases

Answer. (a) Pressure will be maximum in position A because area of contact is minimum in this case and area is inversely proportional to pressure.

lesson 9 Friction

Q1. Very short answer questions :-

1.In which direction does the force of friction act on a moving object ?

2. Write the factors on which friction between the solid surfaces depends.

3.Write the factors on which the frictional force of an object while moving through a fluid depends .

4. What is the advantage of providing rollers on your travelling suitcase ?

5. What type of shoes are worn by the mountaineers and why?

6. Why do wrestlers generally apply oil on their body while going for wresting ?

Q.2. Short answer questions :-

7. List any three harmful effects of friction .

8. List some ways to reduce friction.

9. What is special about streamlined shape?

10. Give reasons for the following :-

(a) Streamline shape of the fish helps it in swimming in water

(b) Car engine gets heated on running

(c) It is always easier to roll an object than to slide it on the surface.

11. Write advantages of friction .

12. Write methods to increase friction .

Lesson 10 Sound

Lesson 11th Chemical effects of Electric current

1.Name one metal which is a good conductor of electricity.

Ans:- Graphite 

2. Name some liquids which are weak conductors of electricity.

Ans:- Pure water, oil, glycerine

3. What makes tap water a conductor of electricity?

Ans:- Salts dissolved in water make the tap water good conductor of electricity.

4. Which of the two , magnetic compass or LED , is better to use in a tester and why?

Ans:-LED is better to use in a tester because it can detect even small amount of current passes . Also it is not affected by magnet nearby. 

Ans 2

1. What is LED ? Why does the LED have one leg short and the other long?

Ans:- LED is a device which glows a very weak current and it's glow is visible even from a distance. It contains one short leg which is connected to negative terminal of battery and one leg long which is connected to positive terminal of batter in the electric circuit.

2. What do you understand about conductors and non Conductors of electricity?

Ans:- Conductors: the substances through which electric current passes are Called conductors. Example: silver and copper etc.

Non Conductors(Insulators) The substances through which electric current donot passes are called non Conductors (Insulators)

Ex- Wood , plastic etc 

3. What happens when electric current is passed through a cut potato?

Ans:- When electric current is passes through cut potato, a greenish blue spot on the cut potato is formed around the positive terminal showing the change in colour on passing electric current through it. 

4. What are the various applications of Electrolysis?

Ans:- done in class

5. In what way is electroplating useful?

Ans:- done in class

6. With the help of an activity explain electroplating of a piece of iron with copper.

Ans:- Activity to explain the electroplating of a piece of iron with copper.

Material required: iron piece , copper plate , battery , switch , wires copper sulphate solution.

Procedure. To the beaker add 50 ml water and dissolve few crystals of Copper sulphate salt . 

Take a battery of suitable strength and set up the circuit through switch.

Tie the iron key to negative terminal of batter and copper plate to positive terminal of battery.

Suspend both the plates (iron and copper) in the copper sulphate solution.

Put the switch on to pass the current for 15-20 mins . 

Switch off the current after some time.

Observation: the iron key is found with a shiny uniform layer of copper. It has been electroplated with copper.

7. What are the various uses of the chemical effects of electric current?

Ans:- Uses of chemical effects of electric current are listed below: 

1. Electrolysis 

2. Change in colour of metal plate 

3. Electroplating

4. Purification of impure metal.

5. Preparing various compounds.

8. Define the following terms:- 

(a)Electrolyte: a substance that produces an electrically conducting solution when dissolved in water is called electrolyte.

(b) Cathode: It is an electrode with negative charge on it. It is connected to negative terminal of battery.

© Electrolysis: It is the decomposition of a compound from its solution on passing electric current through the electrolytes of solution.

(d) anode: It is an electrode with positive charge on it . It is connected to positive terminal of battery.

(e) electroplating: process of depositing a thin film of desired metal over the object by passing current through an electrolyte in its Electrolytic solution.

(f) Galvanising: The process the depositing a layer of zinc over the other metal is called galvanising. 

lesson 12 Some natural phenomena

Lesson 13 Light

1. Name the following:- 

(a) A highly polished glass with a reflecting surface

(b) Irregular reflection of light

(c) Central coloured part of an eye(d) Muscles which hold the lens in the eye in position.

(e) Instrument with three mirrors which shows multiple images.

(f) Angle between incident ray and the normal.

(g) Deficiency of this nutrient causes night blindness

2. Write uses of periscope and plane mirror.

3. Write some common diseases of the human eye.

4. What makes some people colour blind?

5. How many pictures should appear per second on screen in succession to have a moving picture?

6. Write characteristics of an image formed in a plane mirror.

7. Draw diagrams showing regular and diffused reflection.

8. How will you find out how many images wil be formed when two mirrors are placed at different angles?

9. Explain the function of the following parts of human eye:-

(a) Iris (b) rods (c) Retina (d) optic nerve (e) eye lens (f) cones10. What do you mean by short sightedness and long sightedness?

11. What is cataract and what is it's treatment?

Practicals

Syllabus XI AND XII

A.Basic Laboratory Techniques 

• 1. Cutting glass tube and glass rod
• 2. Bending a glass tube
• 3. Drawing out a glass jet
• 4. Boring a cork

B.Characterization and Purification of Chemical Substances 

• 1. Determination of melting point of an organic compound.
• 2. Determination of boiling point of an organic compound.
• 3. Crystallization of impure sample of any one of the following: Alum, Copper Sulphate, Benzoic Acid.

C.Experiments based on pH

1. Any one of the following experiments:

• 1. Determination of pH of some solutions obtained from fruit juices, solution of known and varied concentrations of acids, bases and salts using pH paper or universal indicator.
• Comparing the pH of solutions of strong and weak acids of same concentration. Study the pH change in the titration of a strong base using universal indicator. 
• 2. Study the pH change by common-ion in case of weak acids and weak bases.

D.Chemical Equilibrium One of the following experiments:

• 1. Study the shift in equilibrium between ferric ions and thiocyanate ions by increasing/decreasing the concentration of either of the ions.
• 2. Study the shift in equilibrium between [Co(H2O)6]2+ and chloride ions by changing the concentration of either of the ions.

E.Quantitative Estimation

• 1. Using a mechanical balance/electronic balance.
• 2. Preparation of standard solution of Oxalic acid.
• 3. Determination of strength of a given solution of Sodium hydroxide by titrating it against standard solution of Oxalic acid.
• 4. Preparation of standard solution of Sodium carbonate.
• 5. Determination of strength of a given solution of hydrochloric acid by titrating it against standard Sodium Carbonate solution.

F.Qualitative Analysis

• 1.Determination of one anion and one cation in a given salt
• Cation: Pb2+, Cu2+ As3+, Aℓ3+, Fe3+, Mn2+, Zn2+, Ni2+, Ca2+, Sr2+, Ba2+, Mg2+, NH4+
• Anions: (CO3) 2- , S2- , (SO3) 2- , (NO2) - , (SO4) 2- , Cℓ- , Br- , I- , (PO4) 3- , (C2O4) 2- , CH3COO-, NO3 -
• (Note: Insoluble salts excluded)
• 2.Detection of -Nitrogen, Sulphur, Chlorine in organic compounds.

G.PROJECTS

Scientific investigations involving laboratory testing and collecting information from other sources. A few suggested Projects

• Checking the bacterial contamination in drinking water by testing sulphide ion
• Study of the methods of purification of water
• Testing the hardness, presence of Iron, Fluoride, Chloride, etc., depending upon the regional variation in drinking water and study of causes of presence of these ions above permissible limit (if any).
• Investigation of the foaming capacity of different washing soaps and the effect of addition of Sodium carbonate on it
• Study the acidity of different samples of tea leaves.
• Determination of the rate of evaporation of different liquids.
• Study the effect of acids and bases on the tensile strength of fibers.
• Study of acidity of fruit and vegetable juices.

Note: Any other investigatory project, which involves about 10 periods of work, can be chosen with the approval of the teacher.

Class XII Practicals

A.Surface Chemistry

• (a) Preparation of one lyophilic and one lyophobic sol Lyophilic sol - starch, egg albumin and gum Lyophobic sol - aluminium hydroxide, ferric hydroxide, arsenous sulphide.
• (b) Dialysis of sol-prepared in (a) above.
• (c) Study of the role of emulsifying agents in stabilizing the emulsion of different oils.

B.Chemical Kinetics

• (a) Effect of concentration and temperature on the rate of reaction between Sodium Thiosulphate and Hydrochloric acid.
• (b) Study of reaction rates of any one of the following:
• (i) Reaction of Iodide ion with Hydrogen Peroxide at room temperature using different concentrations of Iodide ions.
• (ii) Reaction between Potassium Iodate, (KIO3) and Sodium Sulphite: (Na2SO3) using starch solution as an indicator (clock reaction).

C.Thermochemistry 

Any one of the following experiments

• (a)Enthalpy of dissolution of Copper Sulphate or Potassium Nitrate.
• (b) Enthalpy of neutralization of strong acid (HCI) and strong base (NaOH).
• (c) Determination of enthaply change during interaction (Hydrogen bond formation) between Acetone and Chloroform.

Electrochemistry

• Variation of cell potential in Zn/Zn2+|| Cu2+/Cu with change in concentration of electrolytes (CuSO4 or ZnSO4) at room temperature.

E.Chromatography 

• (a) Separation of pigments from extracts of leaves and flowers by paper chromatography and determination of Rf values.
• (b) Separation of constituents present in an inorganic mixture containing two cations only (constituents having large difference in Rf values to be provided).

F.Preparation of Inorganic Compounds

• Preparation of double salt of Ferrous Ammonium Sulphate or Potash Alum. Preparation of Potassium Ferric Oxalate.

G.Preparation of Organic Compounds

Preparation of any one of the following compounds

• i) Acetanilide ii) Di -benzalAcetone iii) p-Nitroacetanilide iv) Aniline yellow or 2 - Naphthol Aniline dye.

H.Tests for the functional groups present in organic compounds:

• Unsaturation, alcoholic, phenolic, aldehydic, ketonic, carboxylic and amino (Primary) groups.

I.Characteristic tests of carbohydrates, fats and proteins in pure samples and their detection in given foodstuffs.

J.Determination of concentration/ molarity of KMnO4 solution by titrating it against a standard solution of: 

• (a) Oxalic acid,
• (b) Ferrous Ammonium Sulphate (Students will be required to prepare standard solutions by weighing themselves).

Qualitative analysis

• Determination of one anion and one cation in a given salt

Cation:

• Pb2+, Cu2+ As3+, Al3+ , Fe3+, Mn2+, Zn2+, Ni2+, Ca2+, Sr2+, Ba2+, Mg2+, NH4+ 

Anions:

• (CO3) 2- , S2- , (SO3) 2- , (NO2) - , (SO4) 2- , Cℓ- , Br- , I- , (PO4) 3- , (C2O4) 2- , CH3COO- , NO3 - (Note: Insoluble salts excluded)

INVESTIGATORY PROJECT

Scientific investigations involving laboratory testing and collecting information from other sources A few suggested Projects.

• Study of the presence of oxalate ions in guava fruit at different stages of ripening.
• Study the quantity of casein present in different samples of milk.
• Preparation of soybean milk and its comparison with natural milk with respect to curd formation, the effect of temperature, etc.
• Study of the effect of Potassium Bisulphate as a food preservative under various conditions (temperature, concentration, time, etc.)
• Study of digestion of starch by salivary amylase and effect of pH and temperature on it.
• Comparative study of the rate of fermentation of the following materials: wheat flour, gram flour, potato juice, carrot juice, etc.
• Extraction of essential oils present in Saunf (aniseed), Ajwain (carum), Illaichi (cardamom).
• Study of common food adulterants in fat, oil, butter, sugar, turmeric power, chilli powder and pepper.

Note: Any other investigatory project, which involves about 10 periods of work, can be chosen with the approval of the teacher.

"Carbon and it's componds"

Carbon and its Compound

1. The earth's crust, has only 0.02% carbon in the form of minerals like carbonates bicarbonates, coal, and petroleum).

2. The atmosphere has 0.03% of carbon dioxide.

3. Inspite of its small amount available in nature ,carbon is a versatile elements as it forms the basis for all living organisms and many things which we use

4. Bonding in carbon:

(a) Atomic number of carbon 6

b) Electronic configuration has 2 electrons in K shell and 4 electrons in shell .

In order to attain the noble gas configuration, carbon should either gain 4 electrons or lose 4 electrons or can share it's 4 electrons with some other element

Gain of 4 electrons (to form octet, i.e. 8 electrons in Canion) is difficult because then a nucleus with 6 protons will have to hold extra four electrons e-) 

Loss of 4 electrons (to attain duplet, ie, 2 electrons like He atom in C4+ cations ) is difficult as it requires large amount of energy to remove four electrons .

Carbon, hence, overcomes this difficulty by sharing it's four valence electrons with other atoms of carbon or with atoms of other elements.

These electrons contributed by the atoms for mutual sharing in order to acquire the stable noble gas configuration is called covalency of that atom. Hence, carbon shows TETRACOVALENCY.

The simplest molecule formed by sharing of electrons (covalent bonds) can be represented by electron dot structure.

Fig. 1.1 Electron dot structure for methane (CH4)

5. Allotropes of carbon: The phenomenon by means of which an element can exist in two or more forms, with similar chemical properties but different physical properties is called allotropy and the different forms are called allotropes Carbon shows the allotropic forms: 1. Diamond ,2. Graphite,3. Fullerenes

 Note:- 

» Diamond is the hardest substance whereas graphite is very soft.

» Diamond is used for grinding and polishing of hard materials and graphite is used as a lubricant.

Diamond has three dimensional rigid structure but graphite has hexagonal sheet layer structure.

» Diamond is a bad conductor of electricity but graphite is very good conductor of electricity.

6. Fullerenes: A new category of carbon allotrope, fullerenes are spherical in shape or a soccer ball like. The first fullerene identified was C-60 with 60 carbon atoms arranged like the godesic dome designed by US architect, Buckminster Fuller, hence these are also known as Buckminster Fullerenes or Bucky Ball structures.

7. Cause of versatile nature of carbon : Four main reasons for versatile nature of carbon are:

(a) Catenation: It is the unique property of self linkage of carbon atoms by means of covalent bonds to form straight chains, or branched chains, or the rings of  sizes (as shown below):

(b)Tetracovalency: Due to small size, and presence of four valence electrons, carbon can form four strong bonds with other carbon atoms, hydrogen, oxygen nitrogen, or sulphur, etc. For example, compounds of carbon with hydrogen are called hydrocarbons.

(c) Multiple Bond Formation: Small size of carbon also enables it to form multiple bonds, (ie, double bonds or triple bonds) with other elements as well as with its own atoms. This increases the number of carbon compounds.

 Note:

» Compounds of carbon with double bonds and triple bonds are called as unsaturated compounds while those with carbon-carbon single bonds are called saturated compounds.

» Alkenes (with -C=C-) and Alkynes are hence unsaturated, whereas Alkanes (with-C-C-) are saturated compounds.

(d) Isomerism: The phenomenon by means of which the carbon compounds with same molecular formula show different structures, and properties, eg. A chain of 4 carbon atoms can be written in two ways.

Hence, number of carbon compounds increases to a huge number.

Ques:- Draw the electron dot structure for O2, CO2, H2O, N2, H2 ,C2H2.

8. Hydrocarbons: Large number of hydrocarbons can be classified as:

Note: In open chain, the name of parent chain is derived from the root word and suffix ane, ene or yne is added depending on the type of bond present in a chain

Table 1. Root word used for naming any compound.

Table 2. General formula and suffix used for alkanes, alkenes and alkynes.

Important: No alkene or alkyne is possible with single carbon atom because double or triple bond is not possible between carbon and hydrogen atom. It is only between two carbon atoms.

9. Functional Group:

• An atom or a group of atoms which when present in a compound gives specific properties to it, is called a functional group
• A single line shown along with a functional group is called as its free valency by which it gets attached to a compound by replacing one hydrogen atom or atoms,
• Functional group replacing the hydrogen is also called as heteroatom because it is different from carbon, and can be nitrogen sulphur, or halogen, etc.

Important: Replacement of hydrogen atom by a functional group is always in such a manner that valency of carbon remains satisfied

Table 3. Some functional groups in carbon compounds.

Note: Cl is named as prefix Chloro, Br as Bromo NH2 as Amino and NO2 as Nitro. Important Note: Symbol R " in a formula represents an Alkyl Group which is formed by the removal of one hydrogen atom from an alkane.

10. Homologous series: A series of organic compounds in which every succeeding member differs from the previous one by -CH2 group or 14 amu 

Note: As the molecular mass increases in a series, so physical properties of the compounds show a variation, but chemical properties which are determined solely by a functional group, remains same within a series

11. Nomenclature of Organic Compounds

(I) Trivial or common names: These names were given after the source from which the organic compounds were first isolated, eg. If a compound has one carbon atom, then its common name will have root word form and so on (see table 4).

Table 4. Root word used for writing trivial or common names.

(II)IUPAC name: International Union of Pure and Applied Chemistry gave following rules for naming various compounds

• (I) Identify the number of carbon atoms and write the word root corresponding to it. eg, if number of carbon atoms are three, then word root is prop .
•  (ii) Presence of a functional group is indicated by prefix or suffix as given in table 2 and table 3.
• (iii)If the name of functional group is to be given as a suffix, the last letter 'e' in the name of compound is deleted and suffix is added,eg, ketone with three carbon atoms is named as: Propane-e-Propan 'one- Propanone.
• Alcohol with three carbons is propanol
• Carboxylic acid with three carbons is propanoic acid. 
•  Halogens, in IUPAC, are written as Prefixes, eg, Compound with two carbons and one chloro group is named as chloroethane (C2H5Cl).

Ques :- Write the structures of the following :-

Methane , Ethane , Propane, Butane ,Ethene, Propene, Butene, Pentene, Ethyne, Propyne, Butyne, Pentyne, Methanol, Ethanol ,Propanol, Methanal, Ethanal,Propanal, Methanoic acid, Ethanoic acid, propanoic acid, Propanone,Butanone,Pentanone.

12 Chemical properties of carbon compounds :

Main properties of carbon compounds are

(a) Combustion Reaction

(b) Oxidation Reaction.

(c)Addition Reaction

(di Substitution Reaction

(a) Combustion Reaction: A chemical reaction in which a substance burns in the presence of air of oxygen is called combustion reaction.

Note: Combustion is always a EXOTHERMIC reaction, eg.

Remember

»Saturated hydrocarbons generally give clean flame whereas unsaturated hydrocarbons give sooty flame (because carbon content is more than hydrogen content in these and hence carbon shows incomplete combustion, and appears as soot).

Saturated hydrocarbons can give sooty flame in limited supply of oxygen 

(b) Oxidation Reaction: The addition of oxygen in a compound upon combustion is called oxidation 

In addition to combustion, oxidation can also be brought about by some substances which are capable of giving oxygen to others, ie, Oxidising agents; e.g. Acidified K2Cr2O7 (Potassium dichromate) and alkaline KMnO4 (Potassium permaganate)

Note:

c) Addition Reaction: Addition of a molecule in unsaturated compounds in the presence of a catalyst, to give saturated compound is called an addition reaction, e.g.

Hydrogenation of vegetable oils as shown in the reaction above

(d) Substitution Reaction: The reactions which involve the replacement of an atom or group of atoms from a molecule by another atom without any change in structure in the remaining part of the molecule

CH4 + Cl2 +hv --> CH3Cl +HCl

13. Ethanol (or alcohol)

Colourless liquid, soluble in water, and has a distinct smell and burning taste. Its consumption in small quantities causes drunkenness and can be lethal.

»Reaction with sodium: With sodium, it gives sodium ethoxide and evolves hydrogen gas.

2CH3CH2OH + 2Na --> 2CH3CH2ONa + H2

»Reaction with conc. H2SO4

CH3CH2OH + concm H2SO4 + heat --> CH2=CH2 + H2O

14 Ethanoic Acid : CH3COOH 

Common Name: Acetic Acid

5-8% solution of aortic acid in water is called Vinegar. And 100% pure acetic acid is called Glacial acetic acid because it has m.pt. 290 K and freezes forming glacier like crystals

Reactions of ethanoic acid: 

Esterification:

Saponification: Esters in the presence of acid or base react to give back alcohol and carboxylic acid this is called saponification. This reaction is used in soap formation.

With base :- 

NaOH + CH3COOH --> CH3COONa  + H2O

With carbonates and bicarbonates: It gives salt, CO2 and water

2CH3COOH + Na2CO3 --> CH3COONa + H2O +CO2

CH3COOH + NaHCO3 --> CH3COONa + H2O +CO2

Soaps and Detergents:

Soaps and Synthetic Detergents: Soaps and detergents are substances used for cleaning Soap: Soaps are sodium or potassium salts of higher fatty acids, such as Oleic acid C17H33COOH), Stearic acid (C17H35COOH), Palmitic acid (C15H31COOH), etc. These acids are present in the form of their esters along with glycerol (an alcohol containing three hydroxyl groups). These esters, called 'glycerides are present in fats and oils of animal and vegetable origin.

Preparation of Soap: When an oil or a fat (glyceride) is treated with sodium hydroxide solution, it gets converted to sodium salt of the acid (soap) and glycerol. The reaction is known as saponification.

Detergents: Chemically, detergents are sodium salts of sulphonic acids, ie, detergents contain a sulphonic acid group (-SO3H), instead of a carboxylic acid group (-COOH), on one end of the hydrocarbon 

Soap molecule = Sodium salts of carboxylic acid

Detergent molecules = sodium salts of sulphonic acid 

Fig. 1.3 Long hydrocarbon chain.

The cleansing action of a detergent is considered to be more effective than a soap

Cleansing Action of Soaps and Detergents: The cleansing action of soaps and detergents follows the same principle.

When a soap or detergent is dissolved in water, the molecules gather together as clusters, called micelles. The tails stick inwards and the heads outwards.

In cleansing the hydrocarbon tail attaches itself to oily dirt. When water is agitated, the oily dirt tends to lift off from the dirty surface and dissociates into fragments. This gives an opportunity to other tails to stick to oil. The solution now contains small globules of oil surrounded by detergent molecules. The negatively charged heads present in water prevent the small globules from coming together and form aggregates. Thus, the oily dirt is removed from the object.

NEET previous years Chemistry Q-A

 Class 11

Chapter 4 [Chemical bonding and Molecular structure]

1. Which one of the following sequences represents the correct increasing order of bond angle in the bond angles in the given molecules? 

(a) H2O <OF2<OCl2<ClO2

(b) OCl2<ClO2<H2O<OF2

(c) OF2<H2O<OCl2<ClO2

(d) ClO2<OF2<OCl2<H2O

Ans:- (c) 

Reason:- Water is sp3 hybridised with bond angle 104.5° due to the presence of two lone pairs. OF2 has structure similar to H2O with bond angle 103° due to higher Electronegativity of Fluorine. OCl2 also has similar structure with bond angle 111° because of steric crowding of two chloride atoms. However, ClO2 has π bond character with an odd electron so that bond angle is 118° . 

Class 12

Coordination compounds

1. Which complex compound obeys 18-electron (a) [V(CO)5]  (b) [Fe(NH3)6]2+

(c) [Ni(CO)6] (4) [Mn(H2O)6]2+

Ans:- (b)

Explanation:-(b) The complex which contains 18 valence electrons,follows 18-electron rule.

(a) [V(CO)5]: The number of valence electrons= 5+(2x5)=15e-

(b) [Fe(NH3)6]2+: The number of valence electrons = =6+(6x2)=6+12=18 e-

(c) [Ni(CO)6], : The number of valence electrons=10+(2 × 6)=22 e-

(d) [Mn(H2O)6]2+ : The number of valence electrons=5+(6x2)=17 e-

Thus, only [Fe(NH3)6] follows 18-electron rule.

2.The hybridization, oxidation number of central metal ion and shape of Wilkinson's catalyst are 

(a) dsp2, +1, square planar 

(b) sp3,.  +4, tetrahedral

(c) sp3d, +2, trigonal bipyramidal

(d) d2sp3, +6, octahedral 

Ans:-(a)

Explanation

In Wilkinson's catalyst-(a homogeneous catalyst), (Ph3P)3RhCI, Rh is dsp2 hybridised, has square planar shape and is in +1 oxidation state.

In complex [Rh(Ph3P)3],

 if x= oxidation state of Rh

x+0+(-1)=0

x=+1

3. The oxidation number of S in tetrathionate (S4O6^2-) is 

(a) +5 (b) 0 (c) 2.5 (d) all of these.

Atoms and molecules

 Atoms and Molecules

Introduction:-

Ancient Indian and Greek philosophers have always wondered about the unknown and unseen form of matter.

The idea of divisibility of matter was considered long back in India, around 500 BC. 

An Indian philosopher Maharishi Kanad, postulated that if we go on dividing matter (padarth), we shall get smaller and smaller particles.

Ultimately, a stage will come when we shall come across the smallest particles beyond which further division will not be possible.

He named these particles Parmanu. 

Another Indian philosopher, Pakudha Katyayama, elaborated this doctrine and said that these particles normally exist in a combined form which gives us various forms of matter.

Around the same era, ancient Greek philosophers - Democritus and Leucippus suggested that if we go on dividing matter, a stage will come when particles obtained cannot be divided further.

Democritus called these indivisible particles atoms (meaning indivisible).

All this was based on philosophical considerations and not much experimental work to validate these ideas could be done till the eighteenth century.

By the end of the eighteenth century. scientists recognised the difference between elements and compounds and naturally became interested in finding out how and why elements combine and what happens when they combine.

Antoine L. Lavoisier laid the foundation of chemical sciences by establishing two important laws of chemical combination.

3.1 Laws of Chemical Combination

The following two laws of chemical combination were established after much experimentations by Lavoisier and Joseph L. Proust.

3.1.1 LAW OF CONSERVATION OF MASS:- 

Law of conservation of mass states that mass can neither be created nor destroyed in a chemical reaction.

3.1.2 LAW OF CONSTANT PROPORTIONS:-

Lavoisier, along with other scientists, noted that many compounds were composed of two or more elements and each such compound had the same elements in the same proportions, irrespective of where the compound came from or who prepared it.

In a compound such as water, the ratio of the mass of hydrogen to the mass of oxygen is always 1:8, whatever the source of water.

Thus, if 9 g of water is decomposed. 1 g of hydrogen and 8 g of oxygen are always obtained.

Similarly in ammonia, nitrogen and hydrogen are always present in the ratio 14:3 by mass. whatever the method or the source from which it is obtained.

This led to the law of constant proportions which is also known as the law of definite proportions. 

This law was stated by Proust as "In a chemical substance the elements are always present in definite proportions by mass".

The next problem faced by scientists was to give appropriate explanations of these laws. British chemist John Dalton provided the basic theory about the nature of matter.

Dalton picked up the idea of divisibility of matter, which was till then just a philosophy. He took the name 'atoms' as given by the Greeks and said that the smallest particles of matter are atoms. 

His theory was based on the laws of chemical combination. 

Dalton's atomic theory provided an explanation for the law of conservation of mass and the law of definite proportions.

According to Dalton's atomic theory, all matter, whether an element, a compound or a mixture is composed of small particles called atoms. 

The postulates of this theory may be stated as follows:

All matter is made of very tiny particles called atoms, which participate in chemical reactions.

Atoms are indivisible particles, which cannot be created or destroyed in a chemical reaction.

Atoms of a given element are identical in mass and chemical properties.

Atoms of different elements have different masses and chemical properties.

Atoms combine in the ratio of small whole numbers to form compounds

The relative number and kinds of atoms are constant in a given compound.

You will study in the next chapter that all atoms are made up of still smaller particles.

3.2 What is an Atom?

 The building blocks of all matter are atoms.

How big are atoms?

Atoms are very small, they are smaller than anything that we can imagine or compare with. 

More than millions of atoms when stacked would make a layer barely as thick as this sheet of paper.

 If atoms are so insignificant in size, why should we care about them? 

This is because our entire world is made up of atoms. 

We may not be able to see them, but they are there, and constantly affecting whatever we do. 

Through modern techniques, we can now produce magnified images of surfaces of elements showing atoms.

3.2.1 WHAT ARE THE MODERN DAY SYMBOLS OF ATOMS OF DIFFERENT ELEMENTS?

Dalton was the first scientist to use the symbols for elements in a very specific sense. 

When he used a symbol for an element he also meant a definite quantity of that element. that is, one atom of that element.

Berzilius suggested that the symbols of elements be made from one or two letters of the name of the element.

In the beginning, the names of elements were derived from the name of the place where they were found for the first time.

For example, the name copper was taken from Cyprus. 

Some names were taken from specific colours. 

For example, gold was taken from the English word meaning yellow. 

Now-a-days. IUPAC (International Union of Pure and Applied Chemistry)   is an international scientific organisation which approves names of elements, symbols and units. 

Many of the symbols are the first one or two letters of the element's name in English. 

The first letter of a symbol is always written as a capital letter (uppercase) and the second letter as a small letter (lowercase).

For example:-

hydrogen, H 

aluminium, Al and not AL

(ii) cobalt, Co and not CO.

Symbols of some elements are formed from the first letter of the name and a letter appearing later in the name. 

Examples are: (i) chlorine, Cl (ii) zinc, Zn etc.

Other symbols have been taken from the names of elements in Latin, German or Greek. 

For example, the symbol of iron is Fe from its Latin name ferrum, 

sodium is Na from natrium. 

potassium is K from kalium. 

Therefore, each element has a name and a unique chemical symbol.

3.2.2 ATOMIC MASS

The most remarkable concept that Dalton's atomic theory proposed was that of the atomic mass. 

According to him, each element had a characteristic atomic mass. 

The theory could explain the law of constant proportions so well that scientists were prompted to measure the atomic mass of an atom. 

Since determining the mass of an individual atom was a relatively difficult task. 

Relative atomic masses were determined using the laws of chemical combinations and the compounds formed.

Let us take the example of a compound. carbon monoxide (CO) formed by carbon and oxygen. 

It was observed experimentally that 3 g of carbon combines with 4 g of oxygen to form CO. 

In other words, carbon combines with 4/3 times its mass of oxygen. 

Suppose we define the atomic mass unit (earlier abbreviated as 'amu', but according to the latest IUPAC recommendations. 

It is now written as 'u' - unified mass) as equal to the mass of one carbon atom, then we would assign carbon an atomic mass of 1.0 u and oxygen an atomic mass of 1.33 u. 

However, it is more convenient to have these numbers as whole numbers or as near to a whole numbers as possible. 

While searching for various atomic mass units, scientists initially took 1/ 16 of the mass of an atom of naturally occurring oxygen as the unit. 

This was considered relevant due to two reasons: 

oxygen reacted with a large number of elements and formed compounds.

this atomic mass unit gave masses of most of the elements as whole numbers. 

However, in 1961 for a universally accepted atomic mass unit, carbon-12 isotope was chosen as the standard reference for measuring atomic masses. 

One atomic mass unit is a mass unit equal to exactly one-twelfth (1/12) the mass of one atom of carbon-12. 

The relative atomic masses of all elements have been found with respect to an atom of carbon-12.

Imagine a fruit seller selling fruits without any standard weight with him. He takes a watermelon and says, "this has a mass equal to 12 units" (12 watermelon units or 12 fruit mass units). 

He makes twelve equal pieces of the watermelon and finds the mass of each fruit he is selling, relative to the mass of one piece of the watermelon. 

Now he sells his fruits by relative fruit mass unit (amu), as in Fig. 3.4. 

Similarly, the relative atomic mass of the atom of an element is defined as the average  mass of the atom, as compared to 1/12 the mass of one carbon-12 atom.

3.2.3 HOW DO ATOMS EXIST

Atoms are not able to exist independently. 

Atoms form molecules and ions. 

These molecules or ions aggregate in large numbers to form the matter that we can see, feel or touch.

3.3 What is a Molecule?

A molecule is in general a group of two or more atoms that are chemically bonded together, that is, tightly held together by attractive forces. 

A molecule can be defined as the smallest particle of an element or a compound that is capable of an independent existence and shows all the properties of that substance.

Atoms of the same element or of different elements can join together to form molecules.

3.3.1 MOLECULES OF ELEMENTS

The molecules of an element are constituted by the same type of atoms. 

Molecules of many elements, such as argon (Ar), helium (He) etc. are made up of only one atom of that element.

But this is not the case with most of the non metals. 

For example, 

A molecule of oxygen consists of two atoms of oxygen and hence it is known as a diatomic molecule, O2

If 3 atoms of oxygen unite into a molecule, instead of the usual 2. we get ozone, O3,

 The number of atoms constituting a molecule is known as its atomicity.

Metals and some other elements, such as carbon, do not have a simple structure but consist of a very large and indefinite number of atoms bonded together.

Let us look at the atomicity of some non-metals.

3.3.2 MOLECULES OF COMPOUNDS

Atoms of different elements join together in definite proportions to form molecules of compounds.

Few examples are given in Table 3.4.

3.3.3 WHAT IS AN ION?

Compounds composed of metals and non metals contain charged species. 

The charged species are known as ions. 

lons may consist of a single charged atom or a group of atoms that have a net charge on them. 

An ion can be negatively or positively charged. 

A negatively charged ion is called an 'anion' and 

the positively charged ion, a 'cation. 

Take, for example, sodium chloride (NaCl). Its constituent particles are positively charged sodium ions (Na+) and negatively charged chloride ions (Cl-). 

Ions may consist of a single atom or a group of atoms that have a net charge on them.

A group of atoms carrying a charge is known as a polyatomic ion (Table 3.6).

 We shall learn more about the formation of ions in Chapter 4.

3.4 Writing Chemical Formulae

The chemical formula of a compound is a symbolic representation of its composition. 

The chemical formulae of different compounds can be written easily. 

For this exercise, we need to learn the symbols and combining capacity of the elements.

The combining power (or capacity) of an element is known as its valency.

Valency can be used to find out how the atoms of an element will combine with the atom(s) of another element to form a chemical compound. 

The valency of the atom of an element can be thought of as hands or arms of that atom.

Human beings have two arms and an octopus has eight.

 If one octopus has to catch hold of a few people in such a manner that all the eight arms of the octopus and both arms of all the humans are locked, how many humans do you think the octopus can hold?

 Represent the octopus with O and humans with H. 

Can you write a formula for this combination? 

Do you get OH4, as the formula? The subscript 4 indicates the number of humans held by the octopus.

The valencies of some common ions are given in Table 

The rules that you have to follow while writing a chemical formula are as follows:

the valencies or charges on the ion must balance.

when a compound consists of a metal and a non-metal, the name or symbol of the metal is written first. 

For example: calcium oxide (CaO), sodium chloride (NaCl). iron sulphide (FeS), copper oxide (CuO) etc.. where oxygen, chlorine, sulphur are non metals and are written on the right whereaswhereas calcium, sodium, iron and copper are metals, and are written on the left.

in compounds formed with polyatomic ions, the number of ions present in the compound is indicated by enclosing the formula of ion in a bracket and writing the number of ions outside the bracket.

For example, Mg (OH)2. 

In case the number of polyatomic ion is one, the bracket is not required. 

For example, NaOH.

3.4.1 FORMULAE OF SIMPLE COMPOUNDS

While writing the chemical formulae for compounds, we write the constituent elements and their valencies as shown below. 

Then we must crossover the valencies of the combining atoms.

The simplest compounds, which are made up of two different elements are called binary compounds. 

Examples

1. Formula of hydrogen chloride

Symbol :

Valency:

Formula of the compound would be HCl

2. Formula of hydrogen sulphide

Symbol :

Valency :

Formula: H2S

3. Formula of carbon tetrachloride

Symbol 

Valency 

Formula: CCI4

4. Formula of magnesium chloride

Symbol 

Charge

Formula: MgCl2

Note that in the formula, the charges on the ions are not indicated.

Some more examples:- 

Formula for aluminium oxide:

Symbol

Charge

Formula: 

Formula for calcium oxide:

Symbol

Charge

Formula

Here, the valencies of the two elements are the same. 

You may arrive at the formula Ca2O2. 

But we simplify the formula as CaO.

(c) Formula of sodium nitrate:

Symbol

Charge

Formula

(d) Formula of calcium hydroxide:

Symbol

Charge 

Formula

Note that the formula of calcium hydroxide is Ca(OH)2 and not CaOH2. 

We use brackets when we have two or more of the same ions in the formula. 

Here, the bracket around OH with a subscript 2 indicates that there are two hydroxyl (OH) groups joined to one calcium atom. 

In other words, there are two atoms each of oxygen and hydrogen in calcium hydroxide.

(e) Formula of sodium carbonate:

Symbol

Charge

Formula

In the above example, brackets are not needed if there is only one ion present.

(f) Formula of ammonium sulphate:

Symbol 

Charge

Formula: 

3.5 Molecular Mass and Mole Concept

3.5.1 MOLECULAR MASS

The molecular mass of a substance is the sum of the atomic masses of all the atoms in a molecule of the substance.

It is therefore the relative mass of a molecule expressed in atomic mass units (u).

Example 3.1 (a) Calculate the relative molecular mass of water (H2O).

Solution

 (b) Calculate the molecular mass of HNO3

Solution:

3.5.2 FORMULA UNIT MASS

The formula unit mass of a substance is a sum of the atomic masses of all atoms in a formula unit of a compound.

Formula unit mass is calculated in the same manner as we calculate the molecular mass.

The only difference is that we use the word formula unit for those substances whose constituent particles are ions. 

For example, sodium chloride as discussed above, has a formula unit NaCl. 

Its formula unit mass can be calculated as

1 x 23+1 x 35.5= 58.5 u

Example 3.2 Calculate the formula unit mass of CaCl2

Solution:-

1. Calculate the molecular masses of H2, O2,  CO2, CH4,  CH3OH.

2. Calculate the formula unit masses of ZnO, Na2O. K2CO3 (given atomic masses of Zn= 65 u , Na = 23 u , K = 39 u,  C= 12 u and O =16u)

3.5.3 MOLE CONCEPT

Take an example of the reaction of hydrogen and oxygen to form water:

H2 + O2 --> 2H2O

The above reaction indicates that

two molecules of hydrogen combine with one molecule of oxygen to form two molecules of water, or

4u of hydrogen molecules combine with 32 u of oxygen molecules to form 36 u of water molecules.

We can infer from the above equation that the quantity of a substance can be characterised by its mass or the number of molecules. 

But, a chemical reaction equation indicates directly the number of atoms or molecules taking part in the reaction. 

Therefore, it is more convenient to refer to the quantity of a substance in terms of the number of its molecules or atoms, rather than their masses. 

So, a new unit "mole" was introduced. 

The mole, symbol mol, is the SI unit of amount of substance. 

One mole contains exactly 6.02214076 x 1023 elementary entities. 

This number is the fixed numerical value of the Avogadro constant Or Avogadro number.

The amount of substance, symbol n, of a system is a measure of the number of specified elementary entities.

 An elementary entity may be an atom, a molecule. an ion, an electron. any other particle or specified group of particles. 

The mole is the amount of substance of a system that contains 6.02214076 x 1023 specified elementary entities. 1 mole (of anything)= 6.022 x 1023 in number.

Besides being related to a number, a mole has one more advantage over a dozen or a gross. 

This advantage is that mass of 1 mole of a particular substance is also fixed.

The mass of 1 mole of a substance is equal to its relative atomic or molecular mass in grams. 

The atomic mass of an element gives us the mass of one atom of that element in atomic mass units (u). 

To get the mass of 1 mole of atom of that element, that is, molar mass, we have to take the same numerical value but change the units from 'u' to 'g.

 Molar mass of atoms is also known as gram atomic mass. 

For example, atomic mass of hydrogen 1u. So, gram atomic mass of hydrogen = 1 g.

1 u hydrogen has only 1 atom of hydrogen and 1 g hydrogen has 1 mole atoms. that is. 6.022 x 10 atoms of hydrogen. Similarly,

16 u oxygen has only 1 atom of oxygen, 16 g oxygen has 1 mole atoms, that is. 6.022 x 10 atoms of oxygen.

To find the gram molecular mass or molar mass of a molecule, we keep the numerical value the same as the molecular mass, but simply change units as above from u to g. For example, as we have already calculated. molecular mass of water (H2O) is 18 u. 

From here we understand that 18 u water has only 1 molecule of water. 18 g water has 1 mole molecules of water, that is, 6.022 x 10 23 molecules of water.

Chemists need the number of atoms and molecules while carrying out reactions, and 

for this they need to relate the mass in grams to the number. It is done as follows:

1 mole = 6.022 x 10" number= Relative mass in grams.

 Thus, a mole is the chemist's counting unit.

The word "mole" was introduced around 1896 by Wilhelm Ostwald who derived the term from the Latin word moles meaning a 'heap' or 'pile. 

A substance may be considered as a heap of atoms or molecules. The unit mole was accepted in 1967 to provide a simple way of reporting a large number- the massive heap of atoms and molecules in a sample.

Example 3.3

1. Calculate the number of moles for the following

(1) 52 g of He 

(2) 12.044 x 10 number of He atoms 

Example 3.4 Calculate the mass of the

following:

(1)0.5 mole of N, gas 

(2) 0.5 mole of N atoms

(3)3.011 x 10 number of N atoms

(4) 6.022 x 1023 number of N molecules 

Example 3.5 Calculate the number of particles in each of the following:

(i)46 g of Na atoms 

(ii) 8 g O2, molecules 

(iii)0.1 mole of carbon atom