A 20.0 mL solution of NaOH is neutralized with 39.2 mL of 0.200 M HBr. What is the concentration of the original NaOH solution?

Answer 1

NaOH(aq) + HBr(aq) → NaBr(aq) + H₂O(l)

Molarity = moles of substance (mol) / volume of solution (L)

Moles of HBr = (39.2 mL / 1000) L x 0.200 M = 0.00784 mol

Moles of NaOH = moles of HBr = 0.00784 mol (NaOH:HBr molar ratio is 1:1)

Concentration (molarity) of original NaOH solution = 0.00784 mol / (20.0 mL / 1000) L = 0.392 M

*Answered!