Question

The value of Kw at several different temperatures in given in the table below. What conclusion can be drawn on the basis of this information?

Temperature

0ºC

25ºC

45ºC

Kw

1.14 x 10-15

1.00 x 10-14

5.48 x 10-14





Pure water becomes more alkaline as the temperature is increased.
The ionization of water is an exothermic process.
Pure water becomes more acidic as the temperature is increased.
The pH of pure water decreases as the temperature is increased.

Answer 1

Answer:

The correct answer is:

The pH of pure water decreases as the temperature is increased.

Explanation:

Ionization constant of water :

$2H_2O(l)\rightleftharpoons H_3O^+(aq) + OH^-(aq)$

Water will dissociate into equal amount of hydronium and hydroxide ions

$K_w=[H_3O^+]\times [OH^-]$

As we can see that from the given information that ionic product of water increase with increase in temperature which means concentration of hydronium ion concentration increases.

And according to definition of pH of the solution is a negative logarithm of hydronium ions concentration.

$pH=-\log [H_3O^+]$

The pH of the solution of solution is inversely proportional to the concentration of hydronium ions.

As the hydronium ion concentration of water increases with increase in temperature , the pH of the water will decrease.