Find `[H^(+)]` in a solution whose pH is `3.69`.

Answer

To find the concentration of hydrogen ions \([H^+]\) in a solution with a given pH of 3.69, we can follow these steps:

### Step-by-Step Solution:

1. **Understand the Relationship Between pH and \([H^+]\)**:
The pH of a solution is defined as:
\[ \text{pH} = -\log[H^+] \]
This means that the concentration of hydrogen ions can be found using the inverse of the logarithm.

2. **Set Up the Equation**:
Given that the pH is 3.69, we can set up the equation:
\[ 3.69 = -\log[H^+] \]

3. **Rearranging the Equation**:
To isolate \([H^+]\), we can rearrange the equation:
\[ -3.69 = \log[H^+] \]

4. **Convert Logarithmic to Exponential Form**:
To find \([H^+]\), we take the antilogarithm (base 10) of both sides:
\[ [H^+] = 10^{-3.69} \]

5. **Calculate \([H^+]\)**:
Now, we can calculate the value:
\[ [H^+] = 10^{-3.69} \approx 2.00 \times 10^{-4} \text{ M} \]

### Final Answer:
The concentration of hydrogen ions \([H^+]\) in the solution is approximately:
\[ [H^+] \approx 2.00 \times 10^{-4} \text{ M} \]