Question

What is the pH of $2M$ aluminium nitrate?

Answer 1

Aluminium nitrate is a salt that was derived from the aluminium hydroxide a weak base and a strong acid nitric acid. Upon treatment of aluminium hydroxide and nitric acid. By substituting the value of initial concentration and $p{K_a}$ the value of pH of aluminium nitrate will be obtained.
$pH = \dfrac{1}{2}\left( {p{K_a} - \log a} \right)$
$p{K_a}$ is acid dissociation constant of aluminium nitrate
$a$ is initial concentration.

Complete answer:
pH is defined as the negative logarithm of the hydrogen ion concentration for organic acids. Which means the acid consists of hydrogen atoms in its molecular formula.
For some compounds without hydrogen atoms, the pH value can be written as in the above formula. Which was written in terms of acid dissociation constant and initial concentration.
Aluminium nitrate is a salt that was derived from the aluminium hydroxide, a weak base and a strong acid like nitric acid. The acid dissociation constant of aluminium nitrate is given as $4.95$
The initial concentration can be given as $2M$
Substitute these both values in the above formula,
$pH = \dfrac{1}{2}\left( {4.95 - \log \left( 2 \right)} \right)$
The value of $\log 2$ is equal to $- 0.3$
By substituting the value of $\log 2$ in the above equation,
$pH = \dfrac{1}{2}\left( {4.95 - \left( { - 0.3} \right)} \right)$
By further simplification the value of pH of aluminium nitrate would be $2.62$
Thus, the pH of $2M$ aluminium nitrate is obtained as $2.62$ .

Note:
pH scale was introduced by Sorensen. It has no units. Acids have the value of pH below $7$ . The acid dissociation constant value is constant for chemical compounds like aluminium nitrate at room temperature. As aluminium nitrate is a salt that was obtained from strong acid, it is weakly acidic and has acid dissociation constant $p{K_a}$ value.