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Solving Problems: A Chemistry Handbook
Chemistry: Matter and Change
143
SOLVING PROBLEMS:
A CHEMISTRY HANDBOOK
CHAPTER 14
The mass in grams of water is numerically equal to the volume of
the water in milliliters, because 1 mL water has a mass of 1 g. Thus,
the mass of the solvent (water) is 260.0 g. The mass of the solution
is the sum of the masses of solute and solvent.
Mass of solution ϭ 5.4 g ϩ 260.0 g ϭ 265.4 g
Substitute the mass of solution and the given mass of solute into the
equation for percent by mass and solve.
Percent by mass ϭ ᎏ
m
m
a
a
ss
ss
o
o
f
f
so
so
lu
lu
ti
t
o
e
n
ᎏ ϫ 100
ϭ
ϫ100 ϭ 2.0%
Practice Problems
4. What is the percent by mass of sodium carbonate in a water
solution containing 0.497 g NaCO 3 in 58.3 g of solution?
5. The percent by mass of magnesium chloride in a water solution
is 1.47%. How many grams of solute are dissolved in each
500.00 g of solution?
6. What is the mass of the solvent in Practice Problem 5?
Percent by volume is a method of expressing the concentration of
solute in a solution made by mixing two liquids.
Percent by volume ϭ
ϫ 100
For example, 100 mL of a solution made by mixing water with
50 mL of acetone has a percent by volume of acetone of
(50 mL/100 mL) ϫ 100, or 50%.
Practice Problems
7. What is the percent by volume of isopropyl alcohol in a solution made by mixing 75 mL of the alcohol with enough water
to make 288 mL of solution?
8. What volume of acetone was used to make 3.11 L of a water
solution if the percent acetone by volume is 27.9%?
volume of solute
ᎏᎏ
volume of solution
5.4 g
ᎏ
265.4 g