What is the concentration of the HNO3 solution?

Question

Consider the neutralization reaction.

2 HNO3(aq) + Ba(OH)2 (aq) —> 2 H2O (I) + Ba(NO3)2 (aq)

A 0.120 L sample of an unknown HNO3 solution required 37.9 mL of 0.250 M Ba(OH)2 for complete neutralization. What is the concentration of the HNO3 solution?

Concentration:? M

Answer 1

2 HNO₃(aq) + Ba(OH)₂ (aq) ==> 2 H₂O (I) + Ba(NO₃)₂ (aq) .. balanced reaction

mols Ba(OH)₂ used = 37.9 ml x 1 L / 1000 ml x 0.250 mol / L = 9.475x10^-3 moles

mols HNO₃ present = 9.475x10^-3 mol Ba(OH)₂ x 2 mol HNO₃ / mol Ba(NO₃)₂ = 0.01895 mol HNO₃

Concentration HNO₃ = 0.01895 mols / 0.120 L = 0.158 M (3 sig. figs.)