If pH of a solution is 4, its `[H^+]` is

Options

A. `10^(-2)` M
B. `10^4 ` M
C. `1/(10^4)` M
D. `10^(-6) M`

Answer

To find the concentration of hydrogen ions \([H^+]\) when the pH of a solution is given as 4, we can follow these steps:

### Step-by-Step Solution:

1. **Understand the relationship between pH and \([H^+]\)**:
The pH of a solution is defined by the formula:
\[ \text{pH} = -\log[H^+] \]

2. **Substitute the given pH value**:
We know that the pH is 4. Therefore, we can write:
\[ 4 = -\log[H^+] \]

3. **Rearrange the equation to isolate \([H^+]\)**:
To isolate \([H^+]\), we first take the logarithm on both sides:
\[ \log[H^+] = -4 \]

4. **Convert the logarithmic equation to exponential form**:
Since the base of the logarithm is 10, we can convert the equation:
\[ [H^+] = 10^{-4} \]

5. **Express the concentration in standard form**:
The expression \(10^{-4}\) can also be written as:
\[ [H^+] = \frac{1}{10^4} \]

6. **Final answer**:
Therefore, the concentration of hydrogen ions \([H^+]\) is:
\[ [H^+] = 0.0001 \, \text{mol/L} \quad \text{or} \quad [H^+] = 1 \times 10^{-4} \, \text{mol/L} \]