Question

The value of $p{K}_w$ of water will :

• A. Increases with increase in temperature
• B. Decreases with increase in temperature
• C. Does not change with variation in temperature
• D. Increase till $50{}^{o}C$ temperature and there after decreases.

Answer 1

The correct option is B Decreases with increase in temperature

The value of $K_w$ increases with rise in temperature, because dissociation of water an endothermic process.
$p{K}_w=-\log \left[K_w\right]$
Now, as $K_w$ increases, then $p{K}_w$ i.e. the negative log value therefore it gives the reverse effect.
So, the value of $p{K}_w$ of neutral water decreases with rise in temperature.