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Do Now
• What does percent represent?
• How do you think percent by mass would be calculated?
• Take out Reference Table and open to Table T
k
f
bl
d
bl
PERCENT BY MASS
• Percent by mass formula:
% mass = mass solute (g) X 100
mass solution (g)
Remember, solution = solute + solvent
Also, 1mL of water = 1g of water = 1cm3 of water!
Insecticides
are often
dissolved in
solvents. Their
concentrations
are usually
given as sample
wei ht divided
weight
by solvent
weight
converted to
percent.
Practice Problems
1. What is the percent by mass of a solution in which 5.0 g. of NaCl is dissolved in 80.0 g of water?
0.243 grams NaF per 100 cc.
0.15 grams Fluoride ion per 100 cc.
Practice Problems
2. What is the percent by mass of a solution if 60.0 g. of acetic acid are added to 90 g. of water?
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Practice Problems
3. What is the percent by mass of a solution if 75 g. of NaOH are dissolved in sufficient water to make 100 g. of solution?
Practice Problems
4. What is the percent by mass of a saturated solution of potassium chlorate at 20 °C?
Parts Per Million (ppm)
Parts Per Million formula:
ppm = grams solute x (1,000,000)
grams solution
• Remember, the density of water is 1 g/mL. So if you are given the solution volume, you can easily convert it to grams.
Practice Problems
1. Find the ppm concentration of 0.10 g. of sugar dissolved in 500mL of water.
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Practice Problems
Practice Problems
2. How many grams of solute must be in 2000mL to have a concentration of 8.0 ppm?
3. What is the ppm concentration when 40 g. of solute are dissolved in 22000mL of solution? Practice Problems
Practice Problems
4. How many grams of solute are necessary to make 400mL of a 3.5 ppm solution?
5. How many milliliters of solution will you have if you need to make a 225 ppm solution with 60 g. of solute?
FORMULAS
Molarity measure of
concentration
Molarity by
Dilution
(M) Molarity = moles solute (mol)
liter solution (L)
PERCENT BY
MASS
% mass = mass solute (g) X 100
mass solution (g)
PARTS PER
MILLION (ppm)
ppm = grams solute X (1,000,000)
grams solution
M1x V1=M2xV2
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