Question

Write the chemical equation of the reaction in which the following changes have taken place with an example of each:
(i) Change in colour
(ii) Change in temperature
(iii) Change in state​

Answer 1

(i) Change in colour: Reaction between lead nitrate solution and potassium iodide solution.

Pb(NO3)2(aq)+2KI → PbI2(s)+2KNO3(aq)

In this reaction, colour changes from colourless to yellow.

(ii)Change in temperature: Action of dilute sulphuric acid on zinc.

Zn(s) + H2SO4(aq) → ZnSO4(aq) + H2

In this reaction, heat is evolved

(iii) Formation of precipitate: Action of barium chloride on sodium sulphate.

BaCl2(aq) +Na2SO4(aq) → BaSO4(s) +2NaCl(aq)