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: Concept pH is defined as $-\log_{10}[H_3O^+]$. Thus, $[H_3O^+] = 10^{-pH}$.

Step 2: Meaning Initial $[H_3O^+]_1 = 10^{-4} \text{ M}$. Final $[H_3O^+]_2 = 10^{-5} \text{ M}$.

Step 3: Analysis Ratio $= \frac{10^{-5}}{10^{-4}} = 10^{-1} = 1/10$.

Step 4: Conclusion The concentration becomes one-tenth of the original, meaning it decreases by 10 times. Final Answer: (D)