Question

A solution of ammonia has a pH of 11.8. What is the concentration of OH– ions in the solution?-1.58 x 10^–12 M-6.31 x 10^–3 M-2.20 M-158 M

Answer 1

INFORMATION:

We know that:

- A solution of ammonia has a pH of 11.8

And we must find the concentration of OH– ions in the solution

STEP BY STEP EXPLANATION:

To find it, we need to know that pH & pOH are related by the following equation

`pH+pOH=14`

Now, using the given information, we know that pH = 11.8

Then, replacing the value in the formula

`11.8+pOH=14`

Solving for pOH,

`\begin{gathered} pOH=14-11.8 \\ pOH=2.2 \end{gathered}`

The concentration of OH- ions is given by

`pOH=-log\lbrack OH^-\rbrack`

Replacing the value of pOH,

`2.2=-log\lbrack OH^-\rbrack`

Finally, solving for OH-

`\begin{gathered} -2.2=log\lbrack OH^-\rbrack \\ OH^-=10^(-2.2) \\ OH^-=6.31*10^(-3) \end{gathered}`

Hence, concentration of OH- is 6.31 x 10^-3 M

ANSWER:

6.31 x 10^-3 M