Question

A compound a when dissolved in water and gives compound b and liberates heat compound a is used in whitewashing.Compound b reacts with co2 to form a white precipitate of compound c. Identify compound a , b, c

Answer 1

Slaked lime [(Ca(OH)2] is used for whitewashing. It is obtained when quicklime, CaO reacts with water.

Answer 2

Answer :

• Compound A = CaO (calcium oxide/quick lime).
• Compound B = Ca(OH)₂ (calcium hydroxide/slaked lime).
• Compound C = CaCO₃ (calcium carbonate).

Reactions Involved:

$\bold{1.}\:\rm{\underset{\text{(A)}}{\underset{\text{Calcium oxide}}{CaO}}+H_2O\longrightarrow{}\underset{\text{(B)}}{\underset{\text{Calcium hydroxide}}{Ca(OH)_2}}+Heat}$

$\bold{2.}\:\rm{Ca(OH)_2+CO_2\longrightarrow{}\underset{\text{(C)}}{\underset{\text{Calcium carbonate}}{CaCO_3}}+H_2O}$

$\hrulefill$

Additional Information:

Reaction 1 (explanation):-

• The reaction between compound A and water is a combination reaction. It can be also called an exothermic reaction as heat is produced along with the formation of the product. The product here is calcium hydroxide which is our compound B.

Reaction 2 (explanation):-

• This reaction ( B & carbon dioxide) is a precipitation reaction inn which the white percipitate of calcium carbonate is formed as an insoluble solid mass. This percipitate is our compound C.