Question

An aqueous solution contains 32.7% KCl (wt/wt%). what is the mole fraction of KCl in the solution

Answer 1

The mole fraction of KCl in the solution is 0.1051

calculation

mole fraction of KCl in solution = moles of KCl / total number of moles(moles of KCl +moles of H2O)

moles=mass/molar mass

mass of KCl=32.7g

molar mass of KCl= 39 +35.5

moles of KCl is therefore= 32.7g/74.5 g/mol=0.439 moles

find the moles of H2O= mass of H2O/molar mass

mass of H2O=100-32.7=67.3g

molar mass of H2O=( 1 x2) +16=18 g/mol

moles = 67.3/18 =3.739 moles

total moles=3.739+0.439=4.178 moles

mole fraction is therefore=0.439/4.178=0.1051