# Mass percent and Molality Problem in Solutions

Assume that the density of water is 1.00 g/mL. % eth by volume = V of eth / (V of eth + V of water) * 100%.

A bottle of wine contains 10.5% ethanol by volume. The density of ethanol (C2H5OH) is 0.789 g/cm3. Calculate the concentration of ethanol in wine in terms of mass percent and molality.

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#### Solution Preview

Mass percentage

The mass percentage of a component in a given solution is the mass of the component per 100 g of the solution. That is if Wa is the mass of component A and Wb the mass of component B in a solution, then

mass percent of A = [Wa/(Wa + Wb)] * 100 ...(1)

Similarly volume percent is given by,

Volume percentage ...

#### Solution Summary

The solution involves calculations of mass percentage given the mass of components in a solution. Volume percentage is also calculated, using the volume of components in a given solution. Mass is calculated using the volume and density, and molality is calculated using number of moles and weight of solvent.