Given a 0.1 M solution of each of the following. Which solution has the lowest pH

Options

A. `NaHSO_(4)`
B. `NH_(4)Cl`
C. HCl
D. `NH_(3)`

Explanation

To determine which 0.1 M solution has the lowest pH, we need to analyze the nature of the solutions provided. The solutions typically consist of strong acids, weak acids, neutral salts, or strong bases.

### Step-by-Step Solution:

1. **Identify the Solutions**:
Let's assume we have the following solutions for analysis:
- HCl (strong acid)
- CH₃COOH (weak acid)
- NaCl (neutral salt)
- NaOH (strong base)

2. **Calculate pH for Each Solution**:
- **For HCl**:
- HCl is a strong acid and completely dissociates in water.
- The concentration of H⁺ ions = 0.1 M.
- pH = -log[H⁺] = -log(0.1) = 1.

- **For CH₃COOH**:
- Acetic acid is a weak acid and does not completely dissociate.
- The dissociation constant (Ka) for acetic acid is approximately 1.8 x 10⁻⁵.
- Using the formula for weak acids:
\[ [H⁺] = \sqrt{Ka \times C} = \sqrt{1.8 \times 10^{-5} \times 0.1} \approx 0.00134 \text{ M} \]
- pH = -log(0.00134) ≈ 2.87.

- **For NaCl**:
- Sodium chloride is a neutral salt and does not affect the pH significantly.
- pH ≈ 7.

- **For NaOH**:
- NaOH is a strong base and completely dissociates in water.
- The concentration of OH⁻ ions = 0.1 M.
- To find pH, first calculate pOH:
\[ pOH = -log[OH⁻] = -log(0.1) = 1. \]
- Then, use the relation pH + pOH = 14:
\[ pH = 14 - pOH = 14 - 1 = 13. \]

3. **Compare the pH Values**:
- HCl: pH = 1
- CH₃COOH: pH ≈ 2.87
- NaCl: pH ≈ 7
- NaOH: pH = 13

4. **Conclusion**:
The solution with the lowest pH is the 0.1 M HCl solution, which has a pH of 1.