Answer to Question #151805 in General Chemistry for Tansha Renoe

Question

25.0 cm3 of 0.100 moldm-3 sodium carbonate solution was titrated with dilute phosphoric acid of unknown concentration. 17.60 cm3 of the acid was required to neutralise the sodium carbonate. Find the concentration of the phosphoric acid in moldm-3 and gdm-3

Answer 1

3Na₂CO₃ + 2H₃PO₄ = 2Na₃PO₄ + 3H₂O + 3CO₂

Ca Va / CbVb = na / nb

Ca × 17.60 /(0.1 ×25) = 2/3

Ca = 0.1 × 25 ×2 /(17.60×3)

= 0.095M

Mass concentration = molar concentration × molar mass

= 0.095 × 98 = 9.31g/dm³