When hydrochloric acid is added to cobalt nitrate solution at room temperature, the following reaction takes place and the reaction mixture becomes blue. On cooling the mixture it becomes pink. On the basis of this information mark the correct answer
[Co (H2O)6]3+ (aq) + 4Cl– (aq) ⇋ [CoCl4] 2- (aq) + 6H2O (l)
(pink) (blue)
• [Co (H2O)6]3+ (aq) + 4Cl– (aq) ⇋ [CoCl4] 2- (aq) + 6H2O (l)
(pink) (blue)
Upon cooling of the product formed [CoCl4] 2- (blue) we are getting the reactant back again [Co (H2O)6]3+ (pink) which means shift in Equilibrium to the backward direction hence the backward process of the reaction must be exothermic (as heat is evolved when [CoCl4] 2- becomes the reactant the opposite case). Therefore the forward reaction is endothermic ∆HH value will be positive and (i) ∆H > 0 for the reaction is the correct answer.