Question: What is the molality of a solution prepared by dissolving 86.9 g of diethyl ether, C4H10O, in 425 g of benzene, C6H6?
Answer: 2.76 mol/kg
Explanation:
Formula of morality is moles of solute divided by the mass of the solvent.
Molality = moles of solute/ mass of solvents (kg)
Mass of solvent is 425g = 0.452kg
Moles = mass / molar mass
Mass of diethyl ester = 86.9g
Molar mass of diethyl ether (C4H10O) = 12*4 + 1*10+ 16
= 48+ 10 + 16
= 74g/mol.
So moles of diethyl ester = 86.9 g / 74 g/mol= 1.17 mol
molality = 1.17mol/0.425kg = 2. 75 mol/kg
Answer is 2. 76 mol approximately.
