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In a solution of dichloromethane (CH2Cl2) in 2-pentanone (CH3COC3H7), the mole fraction of dichloromethane is 0.320. If the solution contains only these two components, what is the molality of dichloromethane in this solution?
Expert Answer
molecular mass of dichloromethane is
molecular mass of 2-pentanone is
mole fraction =moles of solute /moles of solvent =moles of CH2Cl2 / moles of CH3COC3H7 = 0.32
molality = moles of solute / mass of solvent in kg
let say the moles of solvent CH3COC3H7 is 1 which implies moles of solute CH2Cl2 is 0.32.
mass of 1 mole of solvent CH3COC3H7 in kg is ( molecular weight of CH3COC3H7) / 1000
=> mass of CH3COC3H7 = 86/1000 mol/kg = 0.86 mol/kg
=molality of given solution is (moles of solute )/ mass of solvent in kg
=> molality = 1/0.86 =1.1627 m
