Question

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.
$\underset{\left(pink\right)}{{\left[Co\right(H_{2}O{)}_5]}^{3+}}\left(aq\right)+4C{l}^{-}\left(aq\right)\rightleftharpoons \underset{\left(blue\right)}{[CoC{l}_4{]}^{2-}}\left(aq\right)+6H_{2}O\left(l\right)$

• A. $\Delta H>0$ for the reaction
• B. $\Delta H<0$ for the reaction
• C. $\Delta H=0$ for the reaction
• D. The sign of $\Delta H$ cannot be predicted on the basis of this information

Answer 1

The correct option is A $\Delta H>0$ for the reaction

$\Delta H>0$ for the reaction
On cooling the mixture reaction moves towards backward direction it means it is an endothermic reaction i.e., $\Delta H>0$