Question

Give two chemical equations as examples for each of the below mentioned characteristics –
a) Change in colour
b) Change in state
c) Change in temperature
(i) Exothermic
(ii) Endothermic
d) Evolution of gas
e) Formation of precipitate

Answer 1

Answer:

(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 of state of the reactants: Example: Ammonia gas reacts with hydrogen chloride gas to produce solid ammonium chloride

(iii)Change in temperature: Action of dilute sulphuric acid on zinc. Zn(s) + H2SO4(aq) → ZnSO4(aq) + H2 In this reaction, heat is evolved