Question

a chemist adds a chemical to pure water and there is a 100 - fold increase in the concentration of hydrogen ions. what is the best approximation of the new ph value? multiple choice 0 5 7 9

Explanation:

Step1: Find pure water pH

Pure water has $\text{pH} = 7$, so $[\text{H}^+] = 10^{-7}\ \text{M}$.

Step2: Calculate new $\text{H}^+$ concentration

100-fold increase: $[\text{H}^+]_{\text{new}} = 100 \times 10^{-7} = 10^{-5}\ \text{M}$.

Step3: Compute new pH

Use $\text{pH} = -\log_{10}[\text{H}^+]$:
$\text{pH} = -\log_{10}(10^{-5}) = 5$

Answer:

C. 5