Determine the molality of an aqueous solution prepared by dissolving 0.112 moles of LiCl in 13.7 moles of H2O

Question

Accidently wrote the wrong numbers so have to post it again correctly. Please help!

Answer 1

Molality (m) is defined as the number of moles of solute per kg of solvent (not solution, the solvent only (eg, in this case H2O).

m = mole / kg  (The m is written as a large lower case m)

First work out how many kg of H2O is in 13.7 moles of H2O

moles = mass / molar mass

molar mass H2O = (1.008 x 2) + 16.0 = 18.016 g/mol

therefore

mass = moles x molar mass

= 13.7 mol x 18.016 g/mol

= 246.82 g

= 0.247 kg

So now

m = moles / kg

= 0.112 mol / 0.247 kg

= 0.453 m