Question

Select the correct option from the following ?

• A. $p{K}_w$ increases with increase in temperature
• B. $p{K}_w$ decreases with increase in temperature
• C. $p{K}_w=14$ at all temperature
• D. $p{K}_w=pH$ at all temperature

Answer 1

The correct option is B $p{K}_w$ decreases with increase in temperature

The value of $K_w$ increases with rise in temperature because dissociation of water is endothermic in nature. Endothermic processes are favoured by an increase in temperature and so as the temperature rises the equilibrium moves further to the right hand side and $K_w$ gets larger.
As $p{K}_w=-lo{g}_{10}\left[K_w\right]$ , So if $K_w$ increases then $p{K}_w$ decreases. Therefore, with increase in temperature $K_w$ increases
therefore, $p{K}_w$ decreases.