Calculate the molarity of each of the following solutions:

Question

(a) 31.5 g of ethanol (C₂H₅OH) in 4.30 × 10²mL of solution

(b) 13.2 g of sucrose (C₁₂H₂₂O₁₁) in 76.5 mL of solution

(c) 8.60 g of sodium chloride (NaCl) in 76.8 mL of solution

Answer 1

Molarity = moles of solute / liter of solution

a) 31.5 g ethanol x 1 mol ethanol / 46.1 g = 0.6833 mols / 0.430 L = 1.60 M (3 sig. figs.)

b) 13.2 g sucrose x 1 mol sucrose / 342.3 g = 0.03944 mols / 0.0765 L = 0.516 M (3 sig. figs.)

c) 8.60 g NaCl x 1 mol NaCl / 58.4 g = 0.1473 mols / 0.0768 L = 1.92 M (3 sig. figs.)