Answer:
6,97x10⁻³ gallons
Explanation:
pH is defined as:
pH = -log [H⁺]
Thus, you need to have, in the end:
10⁻⁷ = [H⁺]
And you have, in the first:
= [H⁺]
The volume of swimming pool is:
700'000 galllons × = 2649787 L
Thus, the moles of H⁺ in the first and in the end are:
First:
× 2649787L = 1,24x10⁻³ moles
End:
× 2649787L = 0,265 moles
Thus, the moles of H⁺ you need to add are:
0,265 - 1,24x10⁻³ = <em>0,26376 moles</em>
These moles comes from 10M HCl, thus, the volume in gallons you need to add are:
=
<em>6,97x10⁻³ gallons</em>
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I hope it helps!