CONCENTRATION complexified
A concentration can be expressed in 4 different ways.
g/L
(grams of solute per liter of solution)
% m/V (grams of solute per 100 mL of solution)
% V/V (mL of solute per 100mL of solution)
% m/m (grams of solute per 100 g of solution)
We will practice the different ways we can calculate
concentration in these ways.
Concentration in g/L
Concentration =
1.
Mass of solute (g)
Volume of solution (L)
Find the concentration in g/L for each of the following:
a) 20 g of NaCl dissolved in 500 mL of solution (0.04 g/L)
b) 2.8 g of NaBr dissolved in 200 mL of solution (14 g/L)
c) 200 mg of KCl dissolved in 75 mL of solution (2.67 g/L)
2.
How many grams of Br2 are needed to make 250 ml of a 4.5 g/L solution?
(1.125 g)
3.
How many grams of HCl are needed to make 500 mL of a 2 g/L solution? (1 g)
4.
How many grams of LiF are needed to make 2.0 L of a 5 g/L solution? (10 g)
5.
Step by step, explain how you would actually prepare 2.0 L of a 5 g/L solution of NaCl in
the lab. (10 g NaCl)
1.
2.
3.
4.
5.
Concentration in % m/V
Mass/Volume Percent =
Mass of solute (g)
Volume of solution (mL)
x 100
You cannot add mass and volume = they are apples and oranges!!!
1.
What is the concentration in percent mass/volume of 150 mL of solution containing 30 g
of solute? (20 %)
2.
What is the concentration by % m/v if 67 g are dissolved to make 1.2 L of solution? (5.6
%)
3.
What volume of a 40 % m/v solution contains 70 g of solute? (175 mL)
4.
What amount of solute is dissolved to make 0.5 L of a 20 % m/v solution?
(100g solute)
5.
What amount of a 75 % m/v solution will be made if 50 g of solute are dissolved?
(66.7 mL solution)
6.
What is the concentration in % m/v if 0.55 kg of solute is dissolved to make 1.5 L of
solution? (36.7 %)
Concentration in % v/v
Volume Percent =
Volume of solute (mL)
Volume of solution (mL)
x 100
1.
What would be the percent by volume of a solution made with 45 mL of alcohol with 125
mL of water? (26.5 %)
2.
What would be the percent by volume of a solution made with 67 ml of acetone mixed
with water to a total volume of 250 mL? (26.8 %)
3.
How would you make 300 mL of a 15 % v/v solution of peroxide?
Label a sketch as to how you would do this. Show all amounts on the sketch.
(45 mL of peroxide)
4.
What volume of water would be used to make 280 mL of a 30 % v/v alcohol solution?
(196 mL of water)
Concentration in % m/m
Mass percent = Mass of solute (g) x 100
Mass of solution (g)
1.
What is the concentration of a solution in mass percent if 25 g of solute are dissolved to
make 150 g of solution? (16.7 %)
2.
What is the concentration of a solution in mass percent if 25 g of solute are dissolved in
150 g of water? (14.3 %)
3.
What is the concentration of a solution in % m/m if 15 g of NaCl are dissolved in 72 g of
water? (17.2 %)
4.
How much solute has to be dissolved to make 65 g of a 20 % m/m solution?
(13 g solute)
5.
How many grams of solution must be made if 80. g of solute are dissolved to make a 35
% m/m solution? (228.6 g solution)
6.
What mass of solute must be dissolve to make 125 g of a 7 % m/m solution?
(8.75 g solute)
7.
What amount of water must be added to 28 g of solute to make an 11 % m/m solution?
(226.5 g water)