Consider a solution containing 0.100 M fluoride ions and 0.126 M hydrogen fluoride. The concentration of hydrogen fluoride after addition of 9.00 mL of 0.0100 M HCl to 25.0 mL of this solution is ________ M.
A)0.0953
B)0.0900
C)0.130
D)0.122
E)0.00976

Question

Quizplus · Accepted Answer

The addition of HCl will convert some fluoride ions to hydrogen fluoride. Calculate moles of HCl added (9.00 mL * 0.0100 M = 0.00009 mol). Initial moles of fluoride ions = 0.100 M * 0.025 L = 0.0025 mol. Moles of fluoride ions after reaction = 0.0025 mol - 0.00009 mol = 0.00241 mol. Initial moles of hydrogen fluoride = 0.126 M * 0.025 L = 0.00315 mol. Moles of hydrogen fluoride after reaction = 0.00315 mol + 0.00009 mol = 0.00324 mol. Total volume = 25.0 mL + 9.00 mL = 34.0 mL = 0.034 L. Concentration of hydrogen fluoride = 0.00324 mol / 0.034 L = 0.0953 M.

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