Fill in the blanks by using the correct word/term given in the brackets.
The pH of `10^(-6)` is ____ than that of `10^(-4)` HCl. (greater/less)

Explanation

To solve the question, we need to determine the pH values of two different concentrations of hydrochloric acid (HCl) and compare them.

### Step-by-Step Solution:

1. **Understand the pH Formula**:
The pH of a solution is calculated using the formula:
\[
\text{pH} = -\log[\text{H}^+]
...