Question

How can I calculate the concentration for the following pH: pH = 4.52 and pH = 7.00

Answer 1

`\begin{gathered} pH\text{ of 4.52 = 3.02}*10^(-5)\text{moldm}^(-3) \\ pH\text{ of 7.00 = }1*10^(-7)\text{moldm}^(-3) \end{gathered}`

Explanations:

To calculate the pH of an aqueous solution, you need to know the concentration of the hydronium ion in moles per liter (molarity). The pH is therefore calculated using the formula;

`\begin{gathered} pH=-\log _(10)\lbrack H^{+^{}}(aq)_{}\rbrack \\ -pH=\log _(10)\lbrack H^+(aq)\rbrack \end{gathered}`

Note that the square bracket denotes concentration.

Recall from the law of logarithm;

`\begin{gathered} \text{If log}_ab=x^{} \\ b=a^x \end{gathered}`

Applying this rule to the pH formula above, we will have:

`\lbrack H^+(aq)\rbrack=10^(-pH)`

For the concentration with a pH of 4.52, its concentration will be derived by substituting this pH value into the concentration formula as shown:

`\begin{gathered} \lbrack H^+(aq)\rbrack=10^(-4.52) \\ \lbrack H^+(aq)\rbrack=3.02*10^(-5)moldm^(-3) \end{gathered}`

Similarly for the concentration of pH of 7.00;

`\begin{gathered} \lbrack H^+(aq)\rbrack=10^(-7) \\ \lbrack H^+(aq)\rbrack=1*10^(-7)\text{moldm}^(-3) \end{gathered}`