The density of an aqueous solution containing 15.0% ethanol (C2H5OH) by mass is

Question

The density of an aqueous solution containing 15.0% ethanol (C2H5OH) by mass is 0.974 g/mL. A) calculate the molality of this solution. B) calculate the solutions molarity. C) what volume of the solution would contain 0.108 mole of ethanol? The density of an aqueous solution containing 15.0% ethanol (C2H5OH) by mass is 0.974 g/mL. A) calculate the molality of this solution. B) calculate the solutions molarity. C) what volume of the solution would contain 0.108 mole of ethanol? A) calculate the molality of this solution. B) calculate the solutions molarity. C) what volume of the solution would contain 0.108 mole of ethanol?

Explanation / Answer

1) let there be 100 g of the solution

thus, mass of ethanol = 15 g

molar mass of ethanol = 46 g/mole

thus, moles of 15 g of ethanol = 15/46 = 0.3261

mass of solvent = 85 g = 0.085 kg

Thus, molality = moles of ethanol/mass of solvent in kg = 0.3261/0.085 = 3.836 m

Now, volume of solution = mass of solution/density = 100/0.974 = 102.67 ml = 0.10267 litres

Hence molarity = moles of ethanol/volume of solution in litres = 0.3261/0.102673.176 M

Mass of 0.108 moles of ethanol = 0.108*46 = 4.968 g

Thus, mass of solution containing 0.108 moles of ethanol = 100*4.968/15 = 33.12 g

Hence volume of solution containg 0.108 moles of methanol = mass of solution/density of solution = 33.12/0.974 = 34.004 ml

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