what is the pH solution in which 15 mL of 0.10 M NaOH has been added to 25 mL of 0.10 M HCl

Answer 1

HCl + NaOH ==> NaCl + H2O
millimols NaOH = 15 x 0.1 = 1.5
mmols HCl = 25 x 0.1 = 2.5
Excess HCl = 2.5-1.5 = 1
(HCl) = (H^+) = 1 mmol/40 mL = ?
Convert to pH.

Answer 2

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