Question

Calculate the molality of a 150% by mass solution of MgCl, FW-95.3 g/mol in H.O. The density of tis solution is 1.127 gim 0.0134 m 0.157 m 1.58 m 1.86 m 11.8 m igator Delete Backspace U 10 pilli

Answer 1

Answer: 1.86 m

Explanation:

Molality of a solution is defined as the number of moles of solute dissolved per kg of the solvent.

$Molality=\frac{n\times 1000}{W_s}$

where,

n = moles of solute

$W_s$ = weight of solvent in g

Given : 15.0 grams of $MgCl_2$ is present in 100 g of solution

Moles of solute $H_2O=\frac{\text {given mass}}{\text {Molar mass}}=\frac{15.0g}{95.3g/mol}=0.16$

mass of solution = 100 g

density of solution = 1.127g/ml

mass of solvent = mass of solution - mass of solute = 100 g - 15.0g = 85.0 g

$Molality=\frac{0.16\times 1000}{85.0g}=1.86$

Thus molality of a 15.0% by mass solution of $MgCl_2$ is 1.86m.