Question

A). To what volume should you dilute 121 mL of an 8.00 M CuCl2 solution so that 52.0 mL of the diluted solution contains 4.44 g CuCl2?

B). Silver nitrate solutions are often used to plate silver onto other metals. What is the maximum amount of silver (in grams) that can be plated out of 5.1 L of an AgNO3 solution containing 3.4 % Ag by mass? Assume that the density of the solution is 1.01 g/mL. Express your answer using two significant figures.

C). An aqueous solution containing 35.6 g  of an unknown molecular (non-electrolyte) compound in 149.9 g of water was found to have a freezing point of -1.3 ∘C.

Calculate the molar mass of the unknown compound.

Express your answer using two significant figures.

Answer 1

A) molar cncentration of diluted solution = 4.44 g/134.45 g/mol x 0.052 L = 0.635 M

Using, M1V1 = M2V2

M1 and M2 are molar concentration of original and diluted solution

V1 and V2 are volumes of original and diluted solutions

So, the final volume of diluted solution = V2 = M1V1/M2 = 8 x 121/0.635 = 1524.41 ml

So we have to dilute the 8 M solution to 1524.41 ml to get final solution having 4.44 g CuCl2 in 52 ml solution

B) 3.4% m/v of 5.1 L AgNO3 has = 3.4 g in 100 ml

So in 1 L = 34 g AgNO3 present in 1 L solution

maximum amount of Ag that can be plated = 34 x 107.87 g/mol/169.87 g/mol = 21.60 g

C) Freezing point = -iKf.m

with,

Kf of water = 1.86 oC/m

freezing point = -1.3 oC

i = 1

We get,

1.3 = 1 x 1.86 x x/0.1499

x = 0.105 moles

molar mass of unknown = 35.6/0.105 = 339.05 g/mol