Untitled - Kelly Walsh High School

Solutions 173
ways of expressing the concentration of solutions. There are a number of these
concentration units that prove to be useful, including percentage, molarity,
molality, and mole fraction.
Percentage
One common way of expressing the relative amount of solute and solvent is
through percentage, amount per hundred. There are three ways that we may
express this percentage: mass percent, mass/volume percent, and volume/volume
percent.
Mass (weight) Percentage
The mass percentage of a solution is the mass of the solute divided by the mass
of the solution and then multiplied by 100% to yield percentage.
Mass % (mass of solute/mass of solution) 100%
A solution is prepared by dissolving 45.2 g of sucrose in 250.0 g of water.
Calculate the mass percent of the solution.
Answer:
Don’t Forget!
Mass %
(45.2 g sucrose)
100% 15.3%
(45.2 250.0) g solution
Add both the solute and solvent masses together to give the solution mass.
Mass/volume Percentage
The mass/volume percent of a solution is the mass of the solute (typically in
grams) divided by the volume (typically in mL) of the solution and then multiplied
by 100% to yield percentage.
Mass/volume % (mass solute/volume of solution) 100%