1 What is the pH of a substance that has a hydrogen ion concentration of 1.2 x10-2 M2 ZpG

Chemistry

2 answers:

Jobisdone [24]2 years ago

5 0

Answer:

Approximately $1.92$ .

Explanation:

The ${\rm pH}$ of a solution is the opposite of the base- $10$ logarithm of that solution's ${\rm H^{+}}$ concentration measured in ${\rm mol \cdot L^{-1}}$ . In other words:

${\rm pH} = - \log_{10} ([{\rm H^{+}])$ .

Using properties of logarithms:

$\begin{aligned}{\rm pH} &= - \log_{10} ([{\rm H^{+}]) \\ &= -\left(\frac{\ln([{\rm H^{+}]})}{\ln(10)}\right)\end{aligned}$ .

In this question, $[{\rm H^{+}}] = 1.2 \times 10^{-2}\; {\rm mol \cdot L^{-1}}$ . Therefore:

$\begin{aligned}{\rm pH} &= - \log_{10} ([{\rm H^{+}]) \\ &= -\left(\frac{\ln([{\rm H^{+}]})}{\ln(10)}\right) \\ &= - \frac{\ln(1.2 \times 10^{-2})}{\ln(10)} \\ &\approx 1.92\end{aligned}$ .

By convention, the number of decimal values in the ${\rm pH}$ should be equal to the number of significant figures in the ${\rm H^{+}}$ concentration of the solution.

In this question, there are two significant figures in the measurement $[{\rm H^{+}}] = 1.2 \times 10^{-2}\; {\rm mol \cdot L^{-1}}$ . Thus, the ${\rm pH}$ result should be rounded to two decimal places.