Question

If I add 1.5 mole of lactose (molar mass 342.3g/mol) to 0.5 kg of water, what is the resulting molality of my solution? choose one of the following.1027.5 m3 m0.002 m256.7 m

Answer 1

Step 1 - Understanding the formula for molality

Molality is a concentratio defined as the quotient between the number of moles of solute and the mass of solvent.

We can state it mathematically as:

$M=\frac{n_{solute}}{m_{\text{solvent}}}$

Step 2 - Setting the data in the equation

The exercise has given us all the needed data: the number of moles of solute (lactose) is 1.5 whereas the mass of solvent (water) is 0.5kg. Therefore:

$M=\frac{1.5}{0.5}=3m$

The molality of this solution will be 3 moles/kg or 3m.