Question

Milk of magnesia, pH = 10.92 Calculate [H +] and [OH﹘]

Answer 1

Answer

[H⁺] = 1.202 x 10⁻¹¹ M and [OH⁻] = 8.319 x 10⁻⁴ M

Explanation

Given:

The pH of milk of magnesia = 10.92

What to find:

To calculate [H⁺] and [OH⁻].

Step-by-step solution:

pH is a measure of hydrogen ion concentration, a measure of the acidity or alkalinity of a solution. The pH scale usually ranges from 0 to 14.

The equation for calculating pH is given by:

$pH=-\log_.[H^+]$

Substitute pH as 10.92 into the formula, we have

$\begin{gathered} 10.92=-\log_.[H^+] \\ \\ .[H^+]=10^{-10.92} \\ \\ .[H]=1.202\times10^{-11}\text{ }M \end{gathered}$

The [H⁺] = 1.202 x 10⁻¹¹ M

For aqueous solutions, the product of hydrogen ion concentration, [H⁺] and hydroxide ion concentration, [OH⁻] equals

$\begin{gathered} .[H^+]\times[OH^-]=1.0\times10^{-14} \\ \\ Putting\text{ }[H^+]=1.202\times0^{-11} \\ \\ 1.202\times0^{-11}\times[OH^-]=1.0\times10^{-14} \\ \\ Divide\text{ }both\text{ }sides\text{ }by\text{ }1.202\times0^{-11} \\ \\ \frac{1.202\times0^{-11}\times[OH^-]}{1.202\times0^{-11}}=\frac{1.0\times0^{-14}}{1.202\times0^{-11}} \\ \\ \therefore\text{ }[OH^-]=8.319\times10^{-4}\text{ }M \end{gathered}$

The [OH⁻] = 8.319 x 10⁻⁴ M