Question

A student wants to prepare 250 mL of a 0.035 mol L-1 solution from the primary standard, anhydrous sodium carbonate. Calculate the mass of anhydrous sodium carbonate that is needed.

Answer 1

n(Na₂CO₃) = C(Na₂CO₃) × V(Na₂CO₃) = 0.035 mol L^-1 × 0.25 L = 0.00875 mol.

m(Na₂CO₃) = n(Na₂CO₃) × M(Na₂CO₃) = 0.00875 mol × (2×23 + 12 + 3×16) = 0.9275 g = 927.5 mg.