Question

If pH of solution changes from 4 to 5, then the $\text{H}_3\text{O}^+$ion concentration of solution}

• A. decreases by one times
• B. increase by one times
• C. increase by 10 times
• D. decrease by 10 times

Hint:

Each unit change in pH corresponds to a 10-fold change in $[H^+]$. Higher pH means lower $[H^+]$.

Answer 1

The Correct Option is D

Step 1: Understanding the Concept:
pH is the negative logarithm (base 10) of the hydronium ion concentration.
Step 2: Key Formula or Approach:
$[\text{H}_3\text{O}^+] = 10^{-\text{pH}}$.
Step 3: Detailed Explanation:
- Initial $\text{pH} = 4 \rightarrow [\text{H}_3\text{O}^+]_1 = 10^{-4}\text{ M}$.
- Final $\text{pH} = 5 \rightarrow [\text{H}_3\text{O}^+]_2 = 10^{-5}\text{ M}$.
Ratio $= [\text{H}_3\text{O}^+]_2 / [\text{H}_3\text{O}^+]_1 = 10^{-5} / 10^{-4} = 10^{-1} = 1/10$.
The concentration becomes one-tenth of the original, which means it decreases by 10 times.
Step 4: Final Answer:
The $\text{H}_3\text{O}^+$ ion concentration decreases by 10 times.