Question

What is the molality of a solution when 1.2 moles MgCl2 is stirred in 1000 grams of water?

Answer 1

1 ml H2O = 1 g H2O

1000 g H2O = 1000 mL H2O = 1 L H2O

molarity = mol/volume

[MgCl2] = 1.2 mol / 1 L = 1.2 M
but one significant digit: 1 M

Answer 2

Answer: The molality of the solution is 1.2 m.

Explanation:

To calculate the molality of the solution, we use the equation:

$\text{Molality of the solution}=\frac{\text{Moles of solute}}{\text{Mass of solvent (in kg)}}$

We are given:

Moles of $MgCl_2$ (solute) = 1.2 moles

Mass of water (solvent) = 1000 g = 1 kg     (Conversion factor: 1 kg = 1000 g)

Putting values in above equation, we get:

$\text{Molality of the solution}=\frac{1.2mol}{1kg}=1.2mol/kg=1.2m$

Hence, the molality of the solution is 1.2 m