Reactions Due to Heat

Q.

The following reaction is used for the preparation of oxygen gas in the laboratory $2{\mathrm{KClO}}_3\left(\mathrm{s}\right)\stackrel{\mathrm{Heat}}{\to }2\mathrm{KCl}\left(\mathrm{s}\right)+3{\mathrm{O}}_2\left(\mathrm{g}\right)$. Which of the following statement(s) is(are) correct about the reaction?

1. It is a decomposition reaction and endothermic in nature.

2. It is a combination reaction.

3. It is a decomposition reaction and accompanied by the release of heat.

4. It is a photochemical decomposition reaction and exothermic in nature.

Q.

Is sublimation endothermic or exothermic?

Q.

Is melting exothermic or endothermic process?

Q.

How does energy change take place in a physical change? Explain

Q.

C. Tick the most appropriate answer:

(v) A lot of heat energy is usually absorbed or given out during a

1. physical change

2. chemical change

3. both (a) and (b)

4. none of these

Q. Identify the reaction type and changes involved during burning of a candle.

1. Change:- Chemical
   Reaction:- Exothermic
2. Change:- Physical
   Reaction:- Exothermic
3. Change:- Physical
   Reaction:- Endothermic
4. Change:- Chemical
   Reaction:- Endothermic

Q.

Boiling is an exothermic change.

1. True
2. False

Q.

Which of the following is a physical change? Explain with reason.

(a) Electrolysis of water gives hydrogen and oxygen.

(b) A bulb glows when electricty is passed through it.

Q. Analyze the reactions given below and fill the suitable answer.
$\mathrm{Reaction}I:\mathrm{Reactant}+\mathrm{Heat}\to \mathrm{Product}\mathrm{Reaction}\mathrm{II}:\mathrm{Reactant}\to \mathrm{Product}+\mathrm{Heat}$
Reaction I is and reaction II is .

1. endothermic
2. exothermic
3. photochemical
4. electrochemical

Q. How many processes shown in the following images are endothermic?

1. 2

Q. Read the following statements and choose the correct option:
Statement 1: Burning of magnesium ribbon is an exothermic reaction.
Statement 2: Decomposition of potassium nitrate is an endothermic reaction.

1. Statement 1 is correct and statement 2 is wrong.
2. Statement 1 is wrong and statement 2 is correct.
3. Both statements are correct.
4. Both statements are wrong.