Question

Identify the type of each of the following reactions. Alan write balanced chemical equation for each.
(a) The reaction mixture becomes warm.
(b) An insoluble substance is formed.


CBSE Class X Science SA 2 (3 Marks)

Answer 1

(a) Exothermic Reaction

CaO + H2O          Ca(OH)2

(b) Double displacement reaction.

BaC12 + Na2SO4                          BaSO4 + NaC1

Answer 2

The reaction mixture becomes warm:

In an exothermic reaction, the reaction mixture becomes warm because heat is released.

Common examples of exothermic reactions are:

photosynthesis, respiration, nuclear fission, combustion reaction, neutralization reaction, the reaction between water and strong acids, anhydrous salts etc. Reactants react with oxygen in the air upon heating to produce the products along with energy.

Reactants \rightarrow Product + Energy

Equation:

Combustion of natural gas:

$\mathrm{CH}_{4}+2 \mathrm{O}_{2} \rightarrow \mathrm{CO}_{2}+2 \mathrm{H}_{2} \mathrm{O}$

An insoluble substance is formed in reactions involving double displacement and precipitation reactions.

When aqueous potassium chloride reacts with aqueous silver nitrate solution, double displacement takes place forming an insoluble precipitate of silver chloride and aqueous potassium nitrate.

$\mathrm{KCl}_{(\mathrm{aq})}+\mathrm{AgNO}_{3(\mathrm{aq})} \rightarrow \mathrm{AgCl}_{(\mathrm{s})}+\mathrm{KNO}_{3(\mathrm{aq})}$