The `pH` of solution having `[OH^(-)]=10^(-7)` is

Options

A. `7`
B. `14`
C. zero
D. `-7`

Explanation

To find the pH of a solution with a hydroxide ion concentration \([OH^-] = 10^{-7}\), follow these steps:

### Step 1: Understand the relationship between \([H^+]\) and \([OH^-]\)
At 25 degrees Celsius, the product of the concentrations of hydrogen ions \([H^+]\) and hydroxide ions \([OH^-]\) is given by the ion product of water:
\[ K_w = [H^+][OH^-] = 10^{-14} \]

### Step 2: Calculate \([H^+]\) concentration
Given \([OH^-] = 10^{-7}\), we can find \([H^+]\) using the equation for \(K_w\):
\[ [H^+] = \frac{K_w}{[OH^-]} = \frac{10^{-14}}{10^{-7}} = 10^{-7} \]

### Step 3: Calculate the pH
The pH is calculated using the formula:
\[ pH = -\log[H^+] \]
Substituting the value of \([H^+]\):
\[ pH = -\log(10^{-7}) \]

### Step 4: Simplify the logarithm
Using the properties of logarithms:
\[ pH = -(-7) = 7 \]

### Final Answer
The pH of the solution is **7**.

---