# How can I calculate the molality when 75.0 grams of MgCl2 is dissolved in 500.0 g of solvent?

Jul 28, 2014

The molality of a solution is calculated by taking the moles of solute and dividing by the kilograms of solvent.

molality = number of moles of solute/ mass of solvent in kg

Mass of solvent = 500 g or 0.500 kg

number of moles of Mg$C {l}_{2}$ = mass of Mg$C {l}_{2}$ / molar mass of Mg$C {l}_{2}$

number of moles of Mg$C {l}_{2}$ = 75 g / 95.2 g $m o {l}^{-} 1$

number of moles of Mg$C {l}_{2}$= 0.78 moles

molality = 0.78moles / 0.5 kg

molality = 1.56 mol $k {g}^{-} 1$