Question

$H_{2}O+H_{2}O\rightleftharpoons H_3{O}^{+}+{OH}^{-}$
The above reverse reaction is an exothermic reaction. What will happen if the temperature is lowered?

• A. The $pH$ will decrease.
• B. The equilibrium will shift to the right.
• C. The concentration of $H_3{O}^{+}$ ions will increase.
• D. The equilibrium will shift to the left.
• E. Temperature does not affect equilibrium.

Answer 1

The correct option is B The equilibrium will shift to the right.

Since the forward reaction is exothermic, lowering the temperature will shift the equilibrium in a direction that counteracts this change.

Hence by decreasing the temperature, the reaction will proceed in that direction which will produce more heat.

Thus, a reaction will proceed in the exothermic direction that is the in the direction of the forward reaction i.e. towards the right.