Question

25g of magnesium chloride (MgCl2) was dissolved in 250 ml distilled water at 25oC. The density of water was 0.9975g/cm3 . Calculate the concentration in molality.

Answer 1

Answer:

[MgCl₂] = 1.05 m

Explanation:

Molality is a type of concentration that indicates the moles of solute in 1000g of solvent.

m = mol/kg.

Our solute is MgCl₂. We convert mass to moles:

25 g . 1mol / 95.21 g = 0.262 moles.

Our solvent is water → 250 mL of H₂O

We use density to determine the mass: density = m / V

Density . V = m → 0.9975 g/mL . 250 mL = 249.3 g

We convert from g to kg = 249.3 g . 1kg/1000g = 0.2493kg

molality → 0.262 mol /0.2493kg = 1.05