Answer to Question #329680 in General Chemistry for Wen

Question

Calculate the mole fraction of a 20% aqueous hydrochloric acid solution

Answer 1

20% HCl solution means

20 g of HCl in 100 g solution

m(H₂O) = 100 - 20 = 80 g

n(HCl) = m(HCl) / Mr(HCl) = 20 g / 36.5 g/mol = 0.548 mol

n(H₂O) = m(H₂O) / Mr(H₂O) = 80 g / 18 g/mol = 4.444 mol

n(solution) = 0.548 mol + 4.444 mol = 4.992 mol

$\chi$(HCl) = n(HCl) / n(solution) = 0.548 mol / 4.992 mol = 0.11