Very Short Answer Questions:

1. Define matter.

Ans- Any substance in the universe which occupies space, has weight and goes in the transformation of both the mass and the energy is called matter. For example, soil, air and water are matter.

2. Differentiate between pure and impure substance.

Ans- The differences between pure and impure substances are tabulated as follows:

Pure substance	Impure substance
matter which composed of only one kind of the constituent and cannot be further splited into simpler units is called the pure substance.	Matter which is composed of two or more than two constituents in any ratio is called the impure substance.
It is perfectly homogenous.	It can either be homogenous or heterogeneous.
For example- elements, compounds, etc.	For example- mixtures, alloys, etc.

 

3. What are elements? How are they classified in major classes?

Ans- The smallest form i.e. the basic constituents of the matter which cannot be splited into any further simpler part by physical or chemical process is called element. Elements are classifies as three major classes and they are:

i. Metals- The lustrous electropositive elements with the properties of producing positive ions and capacity to conduct heat and electricity are metals. For example, sodium, iron, etc.

ii. Non- metals- Those elements which are electronegative and bad conductor of both heat and electricity except graphite and occur in all states are non-metals. For example, chlorine, hydrogen, etc.

iii. Metalloids- Those elements which are the intermediates of metals and non-metals and behave semi-conductors are metalloids. For example, boron, silicon, etc.

4. Write any two differences between inorganic and organic compound.

Ans- The differences between inorganic and organic compounds are tabulated below;

Inorganic Compounds	Organic compounds
Those compounds in which carbon and hydrogen are not necessarily present are called inorganic compound.	Those compounds in which carbon and hydrogen are principle constituent are called organic compounds.
Inorganic compounds are relatively less abundant compounds.	Thanks to the catenation property of carbon, organic compounds are most abundant compounds.
For example- AgCl3, MgO, etc.	For example- CH3COOH, C2H5

 

5. Classify following compounds into pure and impure substances with suitable reason.

A. Air

Ans- Air is an impure substance because it is the mixture of several gases like O₂, CO­_2­, N₂, H₂ and etc.

B. kerosene

Ans- Kerosene is

C. Bronze

Ans- Bronze is an alloy of copper and tin. So, it is an impure substance.

D. Salt solution

Ans- Salt solution is a homogenous solution of salt and water. Thus, it is an impure substance.

6. What types of impurities are separated by sedimentation and decantation process?

Ans- If the constituents of the mixture are a liquid and the solid which is heavier than the liquid, sedimentation and decantation is used for the separation of impurities. 

7. Define filtration, filtrate and residue.

Ans-  

Filtration- The process of separating in-soluble solid impurities from a liquid by passing the mixture through porous membranes is called the filtration. For example, passing the mixture of sand and water through a filter paper is filtration.

Filtrate- The liquid containing the dissolved substance which passes through the pores of the filter paper is called filtrate. For example, water is the filtrate in the mixture of sand and water.

Residue- The insoluble solid left on the filter paper after filtration is called residue. For example, sand is the residuein the mixture of sand and water.

8. Write two main characteristics of a chemical compound.

Ans- The main characteristics of chemical compound are;

They are obtained from both the living and non-living things

They are homogenous throughout their mass.

9. You have a mixture of table salt, sand and camphor, by what sequence of process, you can obtain all the components in pure and dry state?

Ans- By the process of sublimation, we can remove the camphor present in the mixture. Now, we can dissolve the mixture in the water and imply the process of sedimentation and decantation to separate table salt and sand.

Sublimation         →Dissolving in water            →  Sedimentation and decantation

10. Define chemical change and point out its two important characters.

Ans- The permanent change in which the chemical behavior of the substances is also changed as a result of change in the composition of molecules is called chemical change. The two important characters of a chemical change are;

1. New substance(s) is/are formed.

2. It is an irreversible change.

11. Define valency with suitable examples.

Ans- The combining capacity of an atom or radical is called the valency i.e. the number of electrons lost, gained or shared by an atom or a radical to acquire the nearest stable configuration state. For example, the valency of hydrogen is 1 and the valency of zinc is 2.

12. Write molecular formula of following compounds.

Ans-

Glauber’s salt- Na₂SO₄.10H₂O

Aqua fortis- HNO₃

White vitriol- ZnSO₄.7H₂O

Laughing gas- N₂O

13.  Define symbol. Write down the symbol for any four elements derived from their Latin name.

Ans- A symbol is defined as the short algberical representation of elements in terms of alphabet(s). For example, the symbol of hydrogen is H.

Symbol of any four elements derived from their Latin names are Pb (lead), K (potassium), Na (sodium) and Sn (tin).

14. How many electrons and neutrons are present in the symbol ₁₃²⁷Al⁺³?

Ans- As represented in the symbol, there are 10 electrons and (27-13)=14 neutrons.

 

15. What are the essentials of a chemical equation?

Ans- The essentials of a chemical equation are:

It must represent a true chemical reaction.

It must be balanced.

It must be molecular

For example, the reaction of three molecules of hydrogen and a molecule of nitrogen gas catalyzed by Fe and promoted by molybdenum under high pressure and low temperature yields two molecules of ammonia gas.

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16. Define polymerization reactions with an example.

Ans- It can be defined as the process in which several small monomers combine to form a large polymer.

For example, n(H₂C=CH₂) (ethene)                    →                         -(CH­₂-CH₂)_n- (polyethene)

 

17. Define molecular formula. What information you obtain from the molecular formula HNO₃?

Ans- The symbolical representation of any molecule of a compound in the terms of alphabet(s) and number(s) is called molecular formula. For example, H₂O is the molecular formula of water.

Information obtained from the molecular formula HNO₃ are:

I. The given compound is a nitric acid.

II. Hydrogen, nitrogen and oxygen are the elements present in the compound.

III. It is a molecule of nitric acid.

IV. A mole of nitric acid i.e. 6.023 * 10²³ molecules of nitric acid.

V. The molecular mass of the compound is 63 i.e. (1+14+48).

VI. 63 parts by the weight of nitric acid consists 1 part by the weight of hydrogen, 14 parts by the weight of nitrogen and 48 parts by the weight of oxygen. 

18.  Define rearrangement reaction. Give an example of this reaction.

Ans- The type of chemical reaction in which the new product is formed because of internal change in atoms without any loss or gains of atoms is called rearrangement reaction. For example,

NH₄CNO$\mathop\to\limits^\Delta  $         NH₂CONH₂

(Ammonium cyanate)                                (Urea)

 

19. Write chemical formula of baking soda, caustic soda and washing soda. What are their main uses?

Ans- The chemical formula baking soda is NaHCO_3­. Baking soda is used in the bakeries.

The chemical formula of caustic soda is NaOH. It is used as an alkali.

The chemical formula of washing soda is Na₂CO­₃.10H₂O. It is used in making soaps and detergent.

 

20. Write any two major differences between compounds and mixture.

Ans- They are:

Compound	Mixture
Compounds are pure substances composed of two or more atoms of different elements.	Impure substances obtained by the mixing of two or more pure substances are called mixture.
It is formed as a result of chemical change.	It is formed as a result of physical change.
For examples- Water, nitric acid, etc.	For examples- Salt solution, camphor and sand, etc.

 

21. What information do you obtain from following equation?

2H₂ (g) + O₂(g) →2H₂O(l)

Ans- The information we obtain from the given equation are:

I. Hydrogen gas and oxygen gas are involved in the reaction to give water.

II. 2 molecules of hydrogen react with a molecule of oxygen to give 2 molecules of water.

III. 2 moles of hydrogen react with a mole of oxygen to give 2 mole of water.

IV. 4 grams of hydrogen react with 32 grams of oxygen to give 36 mole of water.

V. Mass of hydrogen and oxygen combine in 1:8 ratios and volume of hydrogen and oxygen combine in 1:2 ratios to yield water. 

 

 

22. Why is it necessary to balance the chemical equation?

Ans- It is necessary to balance chemical equation to satisfy law of conservation of mass and impart the correct information.

23.  Define radical with an example.

Ans- An atom or group of atoms which carry certain amount of charge and act as a single unit during the chemical reactions is called radical. For example, CuSO₄ consists of Cu²⁺ and SO₄^2- radicals.

24.  State the law behind balancing the chemical equation.

Ans- The law of conservation of mass is behind the balancing the chemical equation. It states, “The total mass of reactants reacted is equal to the total mass of products formed.”

25. Define hydrolysis reaction with an example.

Ans- Hydrolysis reaction is defined as the chemical reaction done by the water on any given substance to from the product. Water is here a hydrolyzing agent.

For example, FeCl₃(s) + 3H₂O (l)                ↔             Fe(OH)₃ + 3HCl 

26. Define skeleton equation.

Ans- Skeleton equation is defined as the equation which represents the true chemical reaction but is not chemically balanced. For example, Zn + HCl             →                 ZnCl₂ + H₂

27.  Classify the following as the pure substance or mixture

Air- Mixture

Distilled water- Pure substance

Iron- Pure substance

Iodized salt- Mixture

Gasoline- Mixture

Graphite- Pure substance

Milk- Mixture

Diamond- Pure substance

 

Short Answer Questions:

1. How is matter classified? Write a concise note on physical and chemical classification of matter.

Ans- Any substance in the universe which occupies space, has weight and goes in the transformation of both the mass and the energy is called matter. For example, soil, air and water are matter. Matter are classified on the basis of constituents and their properties.

Physical classifications of matter-On the basis of the physical properties, matters are classified into three states. They are:

i) Solid- The state of matter in which the molecules and ions are tightly held and shape and size of the matter is fixed due to high intermolecular interaction is solid state. For example- salt.

ii) Liquid- The state of matter in which the intermolecular force of attraction is only just enough to hold the molecules to each other but not bund them is liquid state. Liquids have fixed volume but not the shape. For example- water.

iii) Gas- The state of matter in which intermolecular force is negligible and intermolecular space is large enough for molecules to move freely is gas state. Gases neither have definite shape or the volume. For example- oxygen.

Chemical classification of matter- On the basis the chemical properties, matter are classified into pure and impure substances;

i) Pure substance- Matter which is compose of only one type of constituents and cannot be further splited into any simpler units is called pure substance. Pure substances are perfectly homogenous and the fixed composition which remains unchanged with mass and time. It can either be an element or a compound. For example- Oxygen, water and metals are pure substances.

ii) Impure substance- Matter which consists of two or more pure homogenous substances in any arbitrary proportion is called impure substance. It can also be termed as mixture. Impure substance can either be homogenous or heterogeneous.All the constituent substances retain their properties in the mixture. They are separable by some particular methods of separation. For example- Milk, gasoline and alloys are impure substances.

 

2. Differentiate between

a. Homogenous and heterogeneous mixture.

 

Homogenous mixture	Heterogeneous mixture
1.A homogenous mixture has uniform composition throughout the sample.	1.A heterogeneous mixture does not have uniform composition throughout the sample.
2. The constituents of homogenous mixture are not easily observed with naked eyes.	2. The constituents of heterogeneous mixture are easily observed with naked eyes.
3. Homogenous mixture needs special process for separation of constituents.	3. Heterogeneous mixture can be easily separated sometimes even by handpicking.
For example- Salt solution is homogenous mixture.	For example- Sand and salt is heterogeneous mixture.

 

b. Elements and compounds.

Elements	Compounds
1. The smallest form i.e. the basic constituents of the matter which cannot be splited into any further simpler part by physical or chemical process is called element.	1. Compounds are pure substances composed of two or more atoms of different elements.
2. Only 92 natural elements are known till date.	2. There are millions of compounds.
3. Element is the simplest form of matter.	3. Two or more atoms are must for a compound to form.
For example- Hydrogen and Oxygen are elements.	For example- Water is a compound.

 

3. Define chemical equation. What information is obtained from balanced chemical equation? What are the limitations of skeleton chemical equation?

Ans- The symbolic representation of a chemical reaction in terms of alphabets, numbers and signs is called the chemical equation. For example,

The reaction of three molecules of hydrogen and a molecule of nitrogen gas catalyzed by Fe and promoted by molybdenum under high pressure and low temperature yields two molecules of ammonia gas.

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The information we obtain form the balanced chemical equation are:

i. Name of reactants and products.

ii. The number of atoms or molecules of reactants and products.

iii. The number of moles of reactants and products.

iv. The mass of the reactants involved and products formed.

 v. The mass-mass, volume-volume, mass-volume ratio of reactants and products.

The limitations of chemical equation are;

i. It does not reflect the total amount of atoms/molecules reacting and forming species involved.

ii. It does not follow law of conservation of mass.

iii. Stoichiometric ratios cannot be obtained.

iv. It is not the true representation of chemical reaction.

 

4. Describe any three types of chemical reactions with an example of each.

Ans- They are described as follows:

i) Combination reaction- The chemical reaction in which two or more reactants combine in order to give a chemical compound is called the combination reaction. Combination reaction is carried out by the application of heat, pressure, electricity or light. For example,

                                 H₂ (g)+ O₂ (g)                    2H₂O (l)

ii) Acid-base neutralisation reaction- In this type of reaction in which the reacting species are acid and base and they are said to neutralize each other producing salt and water. It is also called ‘water forming reaction’. For example,

                                HCl (aq) + NaOH (aq)→ NaCl (aq) + H₂O (l)

 iii) Polymerisation reaction- It can be defined as the process in which several small monomers combine to form a polymer.

For example, n(H₂C=CH₂) (ethene)                      →                        -(CH­₂-CH₂)_n- (polyethene)

 

5. What are the factors required to bring a chemical reaction?

Ans- Chemical reactions are the process to bring out chemical change in the reactants by the application of heat, light, pressure and electricity and produce chemically different products. The factors required to bring a chemical reactions are:

i) Contact- A simple contact between the reactants is essential for any reaction to occur.

ii) Heat- Generally, heat is required to break the strong internuclear bonds and initiate the reaction.

iii) Pressure- High pressure is required for some reactions to occur

iv) Electricity- For combination, decomposition or any other chemical change, electricity is required.

v) Light- Photochemical reactions proceed only in the presence of light.

vi) Catalyst- Catalyst are required to speed up or slow down the rate of reaction.

vii) Sound- Some chemical reaction like decomposition of acetylene into carbon and hydrogen occurs in presence of sound.

6. Write short notes on

a) Displacement reaction- The reaction in which a constituent of a compound replaces the other constituent of the other compound by occupying its position is called displacement reaction.

There are two types of displacement reaction:

Single displacement reaction- In this type of reaction, one element displaces the other element from a compound

Representation of this reaction is A + BX            →                    AX + B.

Examples of single displacement reaction are;

Zn (s) + H₂SO₄ (aq)               →              ZnSO₄ +H₂

Fe (s) + CuSO₄ (aq)             →                Cu (s) + FeSO₄

Double displacement reaction- The process of mutual exchange of radicals of compounds partaking in the formation of two new compounds is called the double displacement reaction. This type of reaction involves the decomposition and recombination. Representation of this reaction is AX + BYAY + BX

Examples of double displacement reactions are;

NaCl + AgNO₃ (aq)            →                AgCl (s) NaNO₂ (aq)

H₂SO₄ + NaCl                 →            HCl (g) + Na₂SO₄

b) Neutralisation reaction­- Neutralisation reaction simply means the acid-base reaction to produce salt and water. In this type of reaction in which the reacting species are acid and base and they are said to neutralize each other producing salt and water. It is also called ‘water forming reaction’. For example,

HCl (aq) + NaOH (aq)           →                NaCl (aq) + H₂O (l)

H₂SO₄ (aq) + KOH (aq)          →                 K₂SO₄ (aq) + H₂O (l)

7.  Balance following equations by hit and trial method.

a) Na₂S₂O₃ + I₂            →  Na₂S₄O₆ + NaI

Ans- S contains maximum number of atoms, it is balanced first and Na is next.

Na₂S₂O₃ + I₂                  → Na₂S₄O₆ + 2NaI

b)CuFeS₂ + O₂→               Cu₂S + FeS + SO₂

Ans- Cu is balanced first followed by S.

2CuFeS₂ + O₂→               Cu₂S + 2FeS + SO₂

c) H₂SO₄ + Al(OH)₃→             Al₂(SO₄)₃ + H₂O

Ans- SO₄ is balanced first, then Al and finally H is balanced to get the balanced equation.

 3H₂SO₄ + 2Al(OH)₃→             Al₂(SO₄)₃ + 3H₂O

d) K₄[Fe(CN)₆] + FeCl₃→              Fe₄[Fe(CN)₆]₃ + KCl

Ans- Balance K at first, followed by Fe and Cl. Cl at last as it appears minimum times.

3K₄[Fe(CN)₆] + 4FeCl₃ →                  Fe₄[Fe(CN)₆]₃ + 12KCl

e) S + NaOH             →               Na₂S + Na₂S₂O₃ + H₂O

Ans- Balance S at first, then Na and O are balanced in a single step.

 3S + 4NaOH              →             Na₂S + Na₂S₂O₃ + H₂O

f) Ag₂S + NaCN           →                Na[Ag(CN)₂] + Na₂S

Ans- Balance Ag at first and then Na, rest are balanced.

Ag₂S + 4NaCN            →              2Na[Ag(CN)₂] + Na₂S

g) NO + H₂O + O₂→              HNO₃

Ans- Balance H at first and then N and O at last because O is the most abundant.

4NO + 2H₂O + 3O₂→               4HNO₃

h) NH₃ + O₂→               NO + H₂O

Ans- Balance H at first and N and balance O to give the following balanced reaction.

 4NH₃ + 5O₂→              4NO + 6H₂O