Chemical Reaction

Q.

What do you mean by chemical reaction?

Q.

What is meant by the skeletal chemical equation?

Q.

What is an example of temperature change?

Q.

List the observations that helps us to determine when a chemical reaction has taken place. [3 MARKS]

Q.

When magnesium ribbon reacts with air, heat and light is produced. The balanced chemical equation is:

$2\text{Mg}+{\text{O}}_2\to 2\text{MgO}$

The reactant(s) in the reaction is/are:

1. Mg

2. $O_2$

3. MgO

4. $M{g}_{2}O$

Q. Write balanced chemical equations for each of the following reactions
1. Carbon dioxide Marble dissolves in hydrochloric acid to give calcium chloride water and carbon dioxide
2. Silver nitrate reacts with copper to produce copper nitrate and silver metal
3. Carbon dioxide gas is passed over lime water to form a precipitate of calcium carbonate
4. Aluminium Sulphate acts with Sodium Hydroxide to form precipitate of aluminium hydroxide and the solution of sodium sulphate
5. Barium Chloride solution reacts with sulphuric acid to form precipitate of Barium sulphate and solution of hydrochloric acid.

Q.

Explain why all decompositions are endothermic reactions.

Q. How many types of chemical reactions are there?

1. 2
2. 3
3. 4
4. 5

Q.

(a) State the various characteristics of chemical reactions.

(b) State one characteristic each of the chemical reaction which takes place when :
(i) dilute hydrochloric acid is added to sodium carbonate

(ii) lemon juice is added gradually to potassium permanganate solution

(iii) dilute sulphuric acid is added to barium chlorid solution

(iv) quicklime is treated with water

(v) wax is burned in the form of a candle

Q.

(a) Give one example of a chemical reaction.

(b) State two characteristics of the chemical reaction which takes place when dilute sulphuric acid is poured over zinc granules.

(c) Give two characteristics of the chemical reaction which occurs on adding potassium iodide solution to lead nitrate solution.

Q.

Is the reaction ${\mathrm{CaCO}}_3\left(\mathrm{s}\right)\to \mathrm{CaO}\left(\mathrm{s}\right)+{\mathrm{CO}}_2\left(\mathrm{g}\right)$ an exothermic reaction?

Q.

One of the following does not happen during a chemical reaction. This is :

(a) Breaking of old chemical bonds and formation of new chemical bonds

(b) Formation of new substances with entirely different properties

(c) Atoms of one element change into those of another element to form new products.

(d) A rearrangement of atoms takes place to form new products.

Q.

Which of the following factors influence the rate of chemical reactions?

1. Nature of reactants

2. Temperature

3. Catalyst

4. Pressure

Q.

Classify each of the following reactions as combination, decomposition, displacement or double displacement reaction. [5 MARKS]

1. ${\text{BaCl}}_2+{\text{H}}_2{\text{SO}}_4\to {\text{BaSO}}_4+2\text{HCl}$
2. $\text{CaO}+{\text{CO}}_2\to {\text{CaCO}}_3$
3. ${\text{CaCO}}_3\to \text{CaO}+{\text{CO}}_2$
4. $2\text{KI}+{\text{Cl}}_2\to 2\text{KCl}+{\text{I}}_2$
5. $2{\text{H}}_2\text{O}\to 2{\text{H}}_2+{\text{O}}_2$

Q. Which of the following is not an information conveyed by a chemical equation?

1. 
   It conveys the names of various reactants and products
2. 
   It conveys the formulae of the reactants and products
3. 
   It conveys about heat change during the reaction
4. 
   
   It conveys how an element forms more than one compound

Q.

(a) What is meant by a chemical reaction ? Explain with the help of an example.

(b) Give one example each of a chemical reaction characterised by :
(i) evolution of a gas

(ii) change in colour

(iii) formation of a precipitate

(iv) change in temperature

(v) change in state.

Q. What is catalyst

Q. What happens when ammonia solution is added
(a) dropwise and then
(b) in excess to the following solutions:
(i) CuSO₄
(ii) ZnSO₄
(iii) FeCl₃
(c) write balanced reactions.

Q.

Which of the following would decrease the rate of a chemical reaction?

1. Using a positive catalyst for the chemical reaction.

2. Increasing the concentration of the reactants.

3. Increasing the temperature of the reactants.

4. Decreasing the surface area of the reactants.

Q.

Which among the following changes are endothermic or exothermic in nature?

Dissolution of sodium hydroxide in water.

Q.

Write balanced equations for the three chemical reactions that take place during the conversion of sulphur dioxide to sulphuric acid in the contact process. Name the catalyst used in the contact process.

Q.

Which of the following does not involve a chemical reaction ?

(a) digestion of food in our body

(b) process of respiration

(c) burning of candle wax when heated

(d) melting of candle wax on heating

Q. Question 11

Electrolysis of water is a decomposition reaction. The mole ratio of hydrogen and oxygen gases liberated during electrolysis of water is

(a) 1:1
(b) 2:1
(c) 4:1
(d) 1:2

Q.

3 (b) By giving at least two examples describe the evolution of gas in a chemical reaction.

Q. Explain the concept of activation energy

Q.

Name the various types of chemical reactions.

Q.

What is a synthesis reaction ?

Q.

Why does chemical reaction occur? What are the different types of chemical reaction.

Q.

Give reasons for the following:

A chemical equation is a short and simple way to represent a chemical reaction.

Q.

Explain, giving one simple example for the following chemical change :

Thermal dissociation