Selina solutions concise chemistry class 9 icse Solutions for Chapter 2 chapter 2 chemical changes and reaction

Differentiate between the scalar and vector quantities, giving two examples of each.

(a) What: is a chemical reaction?

(b) State the conditions necessary for a chemical change or reaction.

Define :

(a) Photochemical reaction (b) Electrochemical reaction. Give one example in each case.

Give an example of each of the following chemical changes.

(a) A photochemical reaction involving

(i) silver salt (ii) water

(b) A reaction involving

(i) blue solution

(ii) formation of a dirty green precipitate

(c) Two gases combine to form a white solid.

(d) Two solids combine to form a liquid.

(e) A reaction where the color change is noticed.

Write the chemical reaction where the following changes observed.

a) Gas is evolved

b) Colour change is noticed

c) Precipitate is formed

d) Physical state is changed

When hydrogen burns in oxygen, water is formed; when electricity is passed through water, hydrogen

and oxygen are given out. Name the type of chemical changes involved in the two cases.

Explain, giving one example for each of the following chemical changes:

(a) Double decomposition (b) Thermal dissociation

(c) Reversible reaction (d) Displacement

Decomposition brought about by heat is known as thermal decomposition. What is the difference

between thermal dissociation and thermal decomposition

What do you understand by a precipitation reaction? Explain with an example

Match the following

Multiple choice:

a. Which of the following is not a characteristic of a chemical change?

i. It is irreversible.

ii. No net energy change is involved.

iii. A new substance is formed.

iv. Involves absorption or liberation of energy.

b. A reaction of a type: AB + CD → AD + CD, involves

i. No chemical change

ii. Decomposition of AB and CD

iii. Exchange of ions of AB and CD

iv. Combination of AB and CD

c. The reaction BaCl2(aq) + H2SO4(aq) → BaSO4(s) + 2HCl(aq) is

i. Displacement reaction

ii. Neutralisation reaction

iii. Decomposition reaction

iv. Double displacement reaction

d. Thermal decomposition of sodium carbonate will produce

i. Carbon dioxide

ii. Oxygen

iii. Sodium hydroxide

iv. No other product

What is a chemical change? Give two examples of a chemical change?

Give an example of a reaction where the following are involved

(a) Evolution of heat

(b) Absorption of heat

(c) High pressure is required

State the main characteristics of chemical reactions. Give at least one example in each case

State the effects of endothermic and exothermic reactions on the surroundings.

Define:

(a) Photochemical reaction

(b) Electrochemical reaction

Give one example in each case

Complete and balance the following reactions:

(a) NaCl(aq) + AgNO3(aq) →

(b) Pb(NO3)2 + KI →

(c) CuCO3—

(d) Pb(NO3)2—

(e) NH3 + O2—-

What do you observe? When

a) Lead nitrate is heated.

b) Silver chloride is exposed to sunlight.

c) Hydrogen peroxide is exposed to sunlight.

d) H2S gas is passed through a copper sulphate solution.

e) Barium chloride is added to sodium sulphate solution

f) Water is added to the quick lime.

g) Sodium chloride solution is added to silver nitrate solution