Chemistry with Solutions and mixtures

Question

A 25.0 mL solution of HBr is neutralized with 16.6 mL of 0.105 M Sr(OH)₂. What is the concentration of the original HBr solution?

Answer 1

2HBr + Sr(OH)2 ==> 2H2O + SrBr2 .. balanced equation

moles Sr(OH)₂ used = 16.6 ml x 1 L / 1000 ml x 0.105 mol / L = 1.74x1^-3 mol

moles HBr neutralized = 1.74x1^-3 mol Sr(OH)₂ x 2 mol HBr / mol Sr(OH)₂ = 3.49x10^-3 mol

Concentration of HBr = 3.49x10^-3 mol / 25.0 ml x 1000 ml / L = 0.140 mol / L = 0.140 M (3 sig. figs.)