Question

What is the pH of solution containing \(5\times 10^{-4} \text{M} \text{H}^+\) ion?

• A. \(4.699\)
• B. \(3.301\)
• C. \(5.401\)
• D. \(3.725\)

Hint:

pH is the negative log of the hydrogen ion concentration; log 5 is 0.699.

Answer 1

The Correct Option is B

Step 1: Quick Bound:
$10^{-4} < 5\times10^{-4} < 10^{-3}$, so pH lies between 3 and 4. That already rules out (A) and (C).

Step 2: Exact Value:
$\log 5 = 0.699$. So $\text{pH} = 4 - 0.699 = 3.301$.

Step 3: Last Option:
3.725 would need $[\text{H}^+] = 1.9\times10^{-4}$, not the given value. The answer is (B).

Final Answer:
Option (B), 3.301. \[ \boxed{\text{(B) } 3.301} \]