Question

1. Calculate Molarity and molality of 50% solution, by volume, of ethanol (d=.789g/mL) in water (d=1.00g/mL).

2.

A. What volume of 6M nickel (II) chloride is needed to make 5.0L of .3m solution?

B. What mass of solid nickel (II) chloride is needed to make the same 5.0L of a 3m solution?

Answer 1

(1) 50 % ethanol solution means 50 mL of ethanol in 50 mL of water and density = mass / volume

Mass of ethanol = density x volume = 0.789x50 = 39.45 g.

No.of moles of ethanol = 39.45 / 46 = 0.8576 mol

Volume of solution, (ethanol+water) = 100 / 1000 = 0.1 L

Therefroe, Molarity = No.of moles of solute / volume of solution in L

M = 0.8576 / 0.1 = 8.576 M

Mass of solvent = 50/1000 = 0.05 kg

Therefore molality = No.of moles of solute / Weight of solvent in kg

m = 0.8576 / 0.05 = 17.152 m