How much (volume) of 0.001 M HCl (aq) should be added to 10 mL of 0.001 M NaOH to change its pH by one unit?

Explanation

To solve the problem of how much volume of 0.001 M HCl should be added to 10 mL of 0.001 M NaOH to change its pH by one unit, we can follow these steps:

### Step 1: Understand the pH Change
A change in pH by one unit means that if the initial pH is 3, we want to change it to 4, or if it is 4, we want to change it to 3. Since we are adding HCl to NaOH, the pH will decrease.

### Step 2: Calculate the Initial Moles of NaOH
We need to calculate the number of moles of NaOH present in the solution.
- Volume of NaOH = 10 mL = 0.01 L
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