Question

What is ionic product of water ?

Answer 1

Ionic product of water: Ionic product of water is defined as the product of molar concentrations of ${\mathrm{H}}^{+}\mathrm{and}{\mathrm{OH}}^{-}$at a specified temperature.

The ionization of water can be represented as:

$\underset{\mathrm{Water}}{{\mathrm{H}}_2\mathrm{O}\left(\mathrm{l}\right)}\rightleftharpoons \underset{\mathrm{Hydrogen}\mathrm{ion}}{{\mathrm{H}}^{+}\left(\mathrm{aq}\right)}+\underset{\mathrm{Hydroxide}\mathrm{ion}}{{\mathrm{OH}}^{-}\left(\mathrm{aq}\right)}$

The ionization constant is given as shown below.
$$\begin{gathered} \mathrm{K}=\frac{\left[{\mathrm{H}}^{+}\right]\left[{\mathrm{OH}}^{-}\right]}{\left[{\mathrm{H}}_2\mathrm{O}\right]} \\ \mathrm{K}\left[{\mathrm{H}}_2\mathrm{O}\right]=\left[{\mathrm{H}}^{+}\right]\left[{\mathrm{OH}}^{-}\right] \\ {\mathrm{K}}_{\mathrm{w}}=\left[{\mathrm{H}}^{+}\right]\left[{\mathrm{OH}}^{-}\right] \end{gathered}$$

Effect of temperature:

• With the rise in temperature, there is increase in concentrations of these ions and hence the value of the ionic product also increases.
• At 25$°\mathrm{C}$, the value of ionic product is $1\times {10}^{-14}$.
• Therefore, ${\mathrm{H}}^{+}={\mathrm{OH}}^{-}=1\times {10}^{-7}$.
• But for different temperatures, these values may be different and can be calculated accordingly.