Question

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

Answer 1

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

Step-by-step 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*10^(-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^+]*[OH^-]=1.0*10^(-14) \\ \\ Putting\text{ }[H^+]=1.202*0^(-11) \\ \\ 1.202*0^(-11)*[OH^-]=1.0*10^(-14) \\ \\ Divide\text{ }both\text{ }sides\text{ }by\text{ }1.202*0^(-11) \\ \\ (1.202*0^(-11)*[OH^-])/(1.202*0^(-11))=(1.0*0^(-14))/(1.202*0^(-11)) \\ \\ \therefore\text{ }[OH^-]=8.319*10^(-4)\text{ }M \end{gathered}`

The [OH⁻] = 8.319 x 10⁻⁴ M