Answer:
pH = 7
Explanation:
pH is defined as -log [H⁺]. In a solution of pH 5:
pH = -log [H⁺]
10^(-5) = [H⁺]
1x10⁻⁵M = [H⁺].
Then, this solution is diluted from 10mL to 1000mL (990mL of water + 10mL of the original solution). That means the solution is diluted:
1000mL / 10mL / 100 times.
If [H⁺] before dilution was 1x10⁻⁵M, after dilution will be:
1x10⁻⁵M / 100 = 1x10⁻⁷M
And pH:
pH = -log [H⁺]
pH = -log 1x10⁻⁷M
pH = 7
