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CHEMISTRY( )PART – 1

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( 4 )

PREFACE

Malcolm Forbes said “Education's purpose is to replace an empty mind with an open one”

and this is something which is always followed by Government of Kerala, Department of Education,

whether through their education system framework or recent enhancement in their curriculum. The

aim of their Curriculum is not just to let learners obtain basic knowledge but to make them life-

long learners.

The purpose of this book is to nurture individuality and thus enhance one's innate potentials

which help in increasing the self-study mode for students. This book strengthens knowledge and

attitude related to subject. This book is designed in such a way that students can set their own goals

and can improve their problem solving and thinking skills.

This book is strictly as per the latest SCERT Kerala Textbook, introduced by SSLC Board in

2016. It follows the latest syllabus prescribed by the board. It contains all types of questions like

Textbook Questions, VSA Questions (Very Short Answer), SA Questions (Short Answer), MCQs

(Multiple Choice Questions) and LA Questions (Long Answer). A synopsis is given for every chapter

which contains important points from that chapter. Each chapter has high quality figures wherever

required for better, fast and clear understanding.

OSWAAL SSLC Question Bank is different and better in terms of High Quality Questions

which are developed by 'OSWAAL Expert Panel' which ensures success in examination. The Question

Bank is arranged ‘Topic-Wise’ where each topic from every chapter is explained in detail. High quality

figures and Flow charts are given to improve retention of concepts.

Through OSWAAL Books students are taught how to think, not what to think. We at

OSWAAL Books try to use quality content, standard language, creativity and high quality figures,

which makes readers to enjoy it because we believe if our readers don't enjoy reading our book then

there is no use in reading it at all. This is one of the reasons that the scope of this book extends from

students to teachers. Teachers can use this book as a perfect teaching guide and students can use

this book for good learning and practice.

At last we would like to thank our authors, editors, reviewers and specially students whom

we request to send suggestions regularly which will help in continuous improvement of this book

and will make this book “One of the Best”. Wish you all Happy Learning.

Why Topic Wise Question Banks are a Better Choice than Previous Year’s Papers ?

Question Banks Previous Years’ Papers

1. Chapter-wise and Topic –wise presentation

in Question Banks facilitates systematic

study.

2. Question Banks can be referred to by the

students throughout the year as well as at

the completion of each chapter in school.

3. Question Banks, take into account any

changes in syllabus or layout and hence are

fully updated and aligned as per the latest

specifications by the Board.

1. Year Wise presentation restricts

methodical flow of learning.

2. These can be referred to only after the

completion of the full syllabus in school.

3. Previous Years' questions cannot be

changed and hence fail to be adept with

the latest Board specifications

–Publisher

CHAPTER

1 STRUCTUREOFATOM

TOPIC-1Theories on Constituents of Matter and Laws of Chemical Combination

QUICK REVIEW Kanada, the Hindu sage who lived in india during 6th century, put forward

the theory that everthing in the universe was made of minute particles called ‘paramanu’.

In 4th century BC, the Greek philosophers Leucippus (460-370 BC) and Democritus (460-370 BC) suggested that the universe was formed of very tiny particles called atoms.

Greek philosophers Plato (428-348 BC) and Aristotle (384-322 BC) did not approve atomic theories but argued that the universe is formed of four elements i.e., soil, air, water and fire.

Lucretius, (99-55 BC), a Roman put forwad the idea that substances were made of indivisible particles.

According to ‘panchabutha’ theory that prevailed in ancient India, the universe was made of Vayu (air), Jalam (water), Bhoomi (earth), Aakasam (ether) and Agni (fire).

Laws of chemical combination : There are two laws of chemical combination as mentioned below : (i) Law of conservation of mass : Antoine Lavoisier (1743-1794) in 1774 proposed the law of conservation of mass is

stated as ‘‘Mass is neither created nor destroyed in a chemical reaction’’. (ii) Law of constant proportion or law of definite proportion : The French scientist Joseph Proust put forward the

law in 1799. According to this law, in a chemical substance the elements are always present in a definite proportion by mass.

These laws are derived from reliable scientific experiments that gave clear indication about the mass and indivisible nature of the minute particles of matter.

Dalton’s Atomic theory : John Dalton (1766-1844) in 1807 introduced the atomic theory to properly explain the laws of chemical combination.

Postulates of Dalton’s Atomic theory : l Matter is made up of very small particales called atoms. l Atoms cannot be divided during chemical reactions. l Atoms can neither be created nor be destroyed. l Atoms of the same elements will be identical in properties, size and mass. l Atoms of different elements will have different properties and masses. l Atoms are the smallest particle that can take part in chemical reactions. l Atoms of two or more elements combine in a small ratio to form compounds. Atoms are building blocks of all matter. The mass of a microscopic particle like atom is very small. Relative Atomic Mass method was used to determine the accurate masses of atoms.

Due to scientific reasons, 112th mass of a carbon atom with atomic mass 12 (Carbon-12) is now accepted as the

atomic mass unit.

TOPIC - 1Theories on Constituents of Matter and Laws of Chemical Combination .... P. 05

TOPIC - 2Discovery of Sub-atomic Particles and Atomic models .... P. 10

TOPIC - 3Isotopes, Isobars and Isotones .... P. 18

6 ] Oswaal Kerala SSLC Question Bank CHEMISTRY, CLASS-IX

FLOWCHARTSLaws of Chemical Combination

Law of conservation of mass Law of definite proportions

Mass can neither be creatednor destroyed in a chemicalreaction

Elements are always presentin a definite proportion by massin a chemical substance

ATOMS

Very smallparticles ofthe matter

Indivisibleduring

chemicalreactions

Neither becreated nordestroyed

Atoms ofsame elements

identical inproperties, size

and mass

Atoms ofdifferent

elements willhave different

propertiesand masses

Atoms oftwo or more

elements combinein a small

ratio to formcompounds

KNOW THE TERMS

Atom : Smallest particle of an element that shows all the properties of an element. Molecule : Smallest particle of an element/compound that is capable of an independent existence and shows all

the properties of that substance. Mass : A measure of the amount of matter in an object. Relative atomic mass : The ratio of the average mass of one atom of an element to one-twelfth of the mass of an

atom of carbon-12.

Atomic mass unit : 112th mass of an atom of carbon – 12, the isotope of carbon with six protons and six neutrons

in its nucleus. One amu is equal to approximately 1.66 × 10– 24 grams.

Very Short Answer Type Questions (1 mark each)

Q. 1. State the law of constant proportion. Ans. Law of constant proportion states that in a chemical

substance, the element are always present in a definite proportion by mass. 1

Q. 2. State the theory proposed by the Hindu sage, Kanada.

Ans. Kanada, the Hindu sage put forward the theory that everything in the universe was made of minute particles called ‘parmanu’. 1

Q. 3. Give the theory proposed by Plato and Aristotle ? Ans. Plato and Aristotle did not approve atomic theories

and argued that the universe is formed of four elements i.e., soil, air, water and fire. 1

Q. 4. What idea was given by Lucretius ? Ans. Lucretius put forward the idea that substances were

made of indivisible particles. 1 Q. 5. Mention the five panchabhuthas ? Ans. Vayu (air), Jalam (water), Bhoomi (earth), aakasam

(ether) and Agni (fire). 1Q. 6. When and who proposed the law of conservation

of mass ?

Ans. Antoine Lavoisier, a French scientist, in 1774 proposed the law of conservation of mass. 1

Q. 7. When and who proposed the law of constant proportion proposed ?

Ans. Joseph Proust, the french scientist, in 1799 proposed the law of constant proportion. 1

Q. 8. What does laws of chemical combination indicate ?

Ans. Laws of chemical combination gave clear indication about the mass and indivisible nature of the minute particles of matter ? 1

Q. 9. Which method was used in past to determine the accurate masses of atoms ?

Ans. In past, the “Relative Atomic Mass’’ method was used to determine the accurate masses of atoms. 1

Q. 10. With which element were the masses of other atoms compared in relative atomic mass method ?

Ans. Hydrogen. 1Q. 11. Which is now a days accepted as the atomic mass

unit (u) ?

STRUCTURE OF ATOM [ 7

Ans. 112th

mass of a carbon atom with atomic mass 12

(carbon -12) is now a days accepted as the atomic mass unit. 1

Short Answer Type Questions-I (2 marks each)

Q. 1. (a) Write the chemical formula of a compound using zinc ion and phosphate ion.

(b) Calculate the ratio by mass of atoms present in a molecule of carbon dioxide.

Ans. (a) Zn3 (PO4)2. 1 (b) The ratio of by mass constituting elements in carbon

dioxide is : CO2 = 12 : 32 = 3 : 8 1Q. 2. State the law of conservation of mass. If 12 gm of

carbon is burnt in the presence of 32 gm of oxygen, how much carbon dioxide will be formed ?

Ans. According to the law of conservation of mass, the matter can neither be created nor destroyed or mass of the reactants is always equal to that of products. 1

C + O2 → CO2 Mass of reactants = 12 + 32 = 44g Mass of products (CO2) = 44g (One mole of carbon reacts with one mole of oxygen

to form one mole of carbon dioxide.) 1Q. 3. Why the law of conservation of mass is followed in

a chemical reaction ? Ans. The identity of an element is not lost. In a chemical

reaction, the old bond break and new bonds are formed. During a chemical change a rearrangement of atoms of different elements takes place resulting in no loss or gain of mass of the species. Mass is conserved. 2

Q. 4. Why the law of conservation of mass in a chemical reaction cannot be verified if it is carried out in an open container ?

Ans. When a chemical reaction is carried out in an open container, some mass in the form of a gas or vapours

may escape into surrounding and hence the mass in the container no longer remains constant. Hence, the law of conservation of mass cannot be verified if products formed in a chemical reaction are gaseous and if they escape into the surrounding. 2

Q. 5. Is there a change in mass when a chemical reaction takes place ?

Ans. No, there is no change in mass when a chemical reaction takes place. 2

Q. 6. Is law of conservation of mass obeyed in all types of chemical reactions ?

Ans. Yes, law of conservation of mass is obeyed in all types of chemical reactions. 2

Q. 7. Does the mass of the flask and its contents change when a chemical reaction is carried out in a conical flask ?

Ans. No, there is no change in the mass of the flask and its contents when a chemical reaction is carried out in a flask. 2

Q. 8. Why should we put a cork on the mouth of the flask when a chemical reaction is carried out in it, to verify the law of conservation of mass ?

Ans. We should put a cork on the mouth of the flask so that the gaseous content of the flask formed may not escape into the surrounding and also no foreign substance enters the system which may affect the results of the reaction. 2

Q. 9. What happens in the conical flask when two solutions barium chloride and sodium sulphate are mixed together ?

Ans. Barium chloride and sodium sulphate react with each other resulting in the formation of sodium chloride and a white precipitate of barium sulphate. 2

Short Answer Type Questions-II (3 marks each)

Q. 1. The percentage of three elements - calcium, carbon and oxygen in a sample of calcium carbonate is give as : calcium = 40 %, carbon = 12 %, oxygen = 48 %

If the law of constant proportion is true, what weight of these elements will be present in 1.5 gm of another sample of calcium carbonate ?

(Atomic mass of Ca = 40u, C = 12u, O = 16u)

Ans. Mass of calcium in 1.5 gm of sample =

40100

1 5× .

= 0.6 gm

Mass of carbon in 1.5 gm of sample =

12100

1 5× .

= 0.18 gm

Mass of oxygen in 1.5 gm of sample =

48100

1 5× .

= 0.72 gm1 × 3 = 3

Q. 2. (a) When 5 gm of calcium is burnt in 2 gm of oxygen, 7 gm of calcium oxide is produced. What mass of calcium oxide will be produced when 5 gm of calcium is burnt in 20 gm of oxygen ? Which law of chemical combination will govern your answer?

(b) Write the chemical formula of calcium oxide.Ans. (a) 7 gm calcium oxide will be produced when 5

gm of calcium is burnt with 2 gm of oxygen leaving 18 gm of oxygen unreacted. The answer will be governed by the law of constant proportion. 2

(b) CaO. 1 Q. 3. Carbon and oxygen react in the ratio of 3:8 by mass

to form carbon dioxide. Calculate the amount of oxygen required to burn

6 gm of carbon. Which law of chemical combination governs your answer. State the law.

8 ] Oswaal Kerala SSLC Question Bank CHEMISTRY, CLASS-IX

Ans. 3 : 8 = 6 : x ⇒ 3x = 6 × 8 ⇒ x = 16 gm 1 Law of constant proportion, governs the answer. 1 It states that in a chemical substance, the elements

are always present in definite proportion by mass. 1Q. 4. Two molecules of hydrogen combine with one

molecule of oxygen to form two molecules of water. Suggest how the above change is in accordance with the law of conservation of mass. [Atomic weight of hydrogen = 1, atomic weight of oxygen = 16]

Ans. 2H2 + O2 → 2H2O Weight of the reaction taking part in the reaction = 2 ( 2 × 1 ) + 2 × 16 = 4 + 32 = 36 gm 1 Weight of the products formed in the reaction = 2 [ ( 2 × 1 ) + 16 ] = 2 [ 2 + 16 ] = 36 gm 1 \ Weight of the reactants = weight of the products

in the reaction. Thus, the above reaction obeys the law of

conservation of mass. 1

Long Answer Type Questions (5 marks each)

Q. 1. (a) If 18 gm of pure water is electrolyzed, 2 gm of hydrogen and 16 gm of oxygen is obtained. Which law of chemical combination is illustrated by this statement ?

(b) State the law of constant proportion. Illustrate with the help of an example.

(c) Which postulate of Dalton’s atomic theory is the result of law of conservation of mass ?

(d) Which point of Dalton’s atomic theory came from law of constant proportions ?

Ans. (a) Law of constant proportion. (b) A compound prepared by any method contains the

same elements in the fixed ratio by mass. For example, H2O contains hydrogen and oxygen in

the ratio 2 : 16 i.e, 1: 8 by mass. (c) Atoms can neither be sub-divided, created nor

destroyed. (d) Atoms of different elements combine in simple

whole number ratios to from chemical compound.

1 + 2 + 1 + 1Q. 2. When 3 gm of carbon is burnt in 8 gm of oxygen,

11 gm of carbon dioxide is produced. What mass of carbon dioxide will be formed when 3 gm of carbon is burnt in 50 gm of oxygen ? Which law of chemical combination will govern your answer ? State the law.

Ans. When 3 gm of carbon is burnt in 8 gm oxygen, 11 gm of carbon dioxide is formed. It means carbon and oxygen are combined in the ratio of 3 : 8 to from carton dioxide. Thus, when there is 3 gm carbon and 50 gm oxygen, then also only 8 gm oxygen will be used and 11 gm of carbon dioxide will be formed. The remaining oxygen is not used.

This indicates the law of definite proportion. According to this law, the element are always present in definite proportion by mass in a chemical substance. All pure samples of a compound contain the same elements combined together in the same proportion by mass. 2 + 1 + 2

Q. 3. With the help of a labelled diagram describe an activity to demonstrate the law of conservation of mass.

Ans. (a)

(b) Materials required : Barium chloride, sodium sulphate, water, conical flask, a small test-tube.

Procedure : Prepare 5 % solution of each : Sodium Sulphate and

barium chloride.A little amount of sodium sulphate solution is taken

in a conical flask and a little solution of barium chloride is taken in an ignition tube.

Hang the tube in the conical flask carefully.Put a cork on the flask and weigh it.Now tilt and swirl the flask so that the two solutions

are mixed up well. Weigh the flask again. (c) Observation :Chemical reaction takes place.Weight of the flask remains same before and after

the reaction. (d) Conclusion :Total mass of the products = Total mass of the

reactants.Law of conservation of mass is proved.

1 + 2 + 1 + 1Q. 4. State the postulates of Dalton’s Atomic theory.Ans. Postulates of Dalton’s Atomic theory are :Matter is made up of very small particles called

atoms.Atoms cannot be divided during chemical reactions.Atoms can neither be created nor be destroyed.Atoms of the same elements will be identical in

properties, size and mass.Atoms of different elements will have different

properties and masses.Atoms are the smallest particle that can take part in

chemical reactions.Atoms of two or more elements combine in a small

ratio to form compounds. 5

STRUCTURE OF ATOM [ 9

Multiple Choice Questions (1 mark each)

Q. 1. For the following chemical equation, if the law of conservation of mass is correct, what would be the number of H2 molecules ?

N2 + H2 → 2 NH3

(a) 2 (b) 3 (c) 4 (d) 6

Ans. (b) 3. (N2 + 3H2 → 2NH3)Q. 2. Which of the following reaction is not suitable

to verify the law of conservation of mass in a chemical reaction ?

(a) Precipitation reaction (b) Displacement reaction (c) Redox reaction (d) Nuclear reaction

Ans. (d) Nuclear reactionQ. 3. 28 gm nitrogen combines with 6 gm hydrogen to

form ammonia gas. If the law of conservation is true, find the mass of ammonia gas ?

(a) 28 gm (b) 6 gm (c) 22 gm (d) 34 gm Ans. (d) 34 gm. (2NH3 = 34 gm)Q. 4. After carrying out the experiment of conservation

of mass with the help of following reaction. Reena was asked to identify the chemical formula of the precipitate formed :

BaCl2 (aq) + NaSO4 (s) + BaSO4(s) + 2 NaO (aq) The correct answer would be : (a) NaCl (b) BaSO4 (c) BaCl4 (d) Na2SO4

Ans. (b) BaSO4.Q. 5. While verifying the law of conservation of mass

in a chemical reaction we take two reactants separately in a vessel and weigh these contents more carefully :

(a) Only before the reaction (b) Only after the reaction (c) Both before and after the reaction (d) Immediately after mixing the reactants

Ans. (c) Both before and after the reactionQ. 6. In an experiment to verify the law of conservation

of mass in a chemical reaction we take one reactant in a small tests tube and the other reactant in conical flask. Before chemical reactant to take place between these two reactants we put a cork on the mouth of the flask to ensure that :

(a) Reactants do not escape out (b) Products do not escape out (c) Gaseous products do not escape out (d) No heat transfer may take place

Ans. (c) Gaseous products do not escape out

Q. 7. Barium chloride reacts with sodium sulphate to form barium sulphate and sodium chloride. In an experiment 20.8gm of barium chloride reacted. with 14.2 gm of sodium sulphate to form 11.7 g sodium chloride. The amount of barium sulphate formed in the above reaction will be :

(a) 35 gm (b) 23.7 gm

(c) 23.3 gm (d) 23.0 gm

Ans. (c) 23.3 gm.

(Amount of barium sulphate = [(20.8 + 14.2) – 11.7 ] gm =23.3 gm)

Q. 8. Colours of barium chloride and sodium sulphate solutions are :

Ans (a) White and blue respectively

(b) White and white respectively

(c) Blue and white respectively

(d) Green and blue respectively

Ans. (b) white and white respectively

Q. 9. During an experiment to verify law of conservation of mass, following reaction was performed by Ramesh :

BaCl2 (aq) + Na2SO4 (aq) → BaSO4 (s) + 2 NaCl (aq)

208.5 gm 142 gm x gm 117 gm

The correct set of observation is :

(a) 58.5 gm of BaSO4 in the form of gas is formed.

(b) 233.5 gm white precipitate of BaSO4 is formed.

(c) 233.5 gm of black precipitate of BaSO4 is formed

(d) 133.5 gm of clear solution of BaSO4 is formed

Ans. (b) 233.5 gm white precipitate of BaSO4 is formed.

[ (208.5 + 142) – 11.7 ] gm = 233.5 gm ]

Q. 10. Study the figure (s) given below and identify which amongst them is the correct setup to establish the law of conservation of mass.

Thread

BaCl2

Na2 4SO

BaCl2solution

Sodiumsulphate

(a) (b)

Thread

BaCl2

Na2 4SO

BaCl2

(c) (d)

Oswaal Kerala SSLC Question Bank ForClass 9 Chemistry (Part-1) With

Complete Solutions For 2017 Exam

Publisher : Oswaal Books ISBN : 9789386177582 Author : Panel Of Experts

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