Question

\(1.0 \times 10^{-4}\,\text{M}\) HCl is diluted 10 times. The pH of the final solution is:

• A. between 3 and 4
• B. between 4 and 5
• C. between 6 and 7
• D. equal to 7

Hint:

When concentration is \(\ge 10^{-5}\,\text{M}\), water contribution can be ignored.

Answer 1

The Correct Option is B

Step 1: Initial concentration of HCl \[ [\text{HCl}] = 1.0 \times 10^{-4}\,\text{M} \] After dilution by 10 times: \[ [\text{H}^+]_{\text{new}} = \frac{10^{-4}}{10} = 10^{-5}\,\text{M} \] Step 2: Since \(10^{-5} \gg 10^{-7}\), contribution of water is negligible. Step 3: Calculate pH: \[ \text{pH} = -\log(10^{-5}) = 5 \] Thus, pH lies between 4 and 5.