Question

Find the pH of the solution if \( [\text{H}^+] = 2 \times 10^{-4} \, \text{mol/L} \).

• A. 3.0
• B. 3.7
• C. 4.5
• D. 5.0

Hint:

To calculate the pH, use the formula \( \text{pH} = -\log[\text{H}^+] \). Remember that the concentration of hydrogen ions determines the acidity of the solution.

Answer 1

The Correct Option is B

The pH of a solution is calculated using the formula: \[ \text{pH} = -\log[\text{H}^+] \] Where \( [\text{H}^+] \) is the concentration of hydrogen ions in the solution.

1. Step 1: Substitute the given value of \( [\text{H}^+] \). We are given \( [\text{H}^+] = 2 \times 10^{-4} \, \text{mol/L} \). Substituting this value into the pH formula: \[ \text{pH} = -\log(2 \times 10^{-4}) \]

2. Step 2: Simplify the expression. Using logarithmic properties: \[ \text{pH} = -\log(2) - \log(10^{-4}) = -\log(2) + 4 \] Since \( \log(2) \approx 0.3010 \), we have: \[ \text{pH} = -0.3010 + 4 =
3.7 \] Thus, the pH of the solution is \(
3.7 \).