Concentration Practice
The concentration of a solution is defined as the amount of solute in a certain amount of
solvent. The solvent is commonly water, with something else dissolved in it. Here are the basic
steps to solving any concentration problem, done as a worked example:
What mass of salt, in grams, would you need to add to 100mL of water to make a solution
with a concentration of 800 ppm.
1. Figure out which equation that you need to use, and rearrange it to isolate the variable that
you are trying to find.
Metric Conversions
2. Convert units so that any common measurements are in the same units.
800 ppm = 800 mg/L
100 mL = 0.1 L
1 g = 1000 mg
1 L = 1000 mL
1 ppm = 1g/1000000g = 1 mg/L
3. Plug the given values into the equation, being sure to put them in the right places (see common units
chart on the side).
Common Units
mass – mg/g/kg
volume – mL/L
concentration – mg/L, g/L, ppm
4. Convert to the desired units.
80 mg = 0.08 g
5. Answer the original question.
You would need 0.08 g of salt.
Complete the practice problems on the following page, on a separate piece of paper. Show
your work, and do every step (Don’t be lazy!!). I have included the answers at the end, so that
you can CHECK your work.
1. Calculate the concentration (in g/L) of a solution made by dissolving 2 g of sugar in 100 mL of
water.
2. How much salt would you need to add to 1 L of water in order to make a solution with a
concentration of 800 ppm?
3. Determine the concentration (in ppm) of a solution prepared by mixing 10 g of salt with 400
mL of water.
4. You want to make chocolate milk with a concentration of 30 g/L. How much chocolate
powder would you need to add to 450 mL of milk to make your drink?
5. You add 5 g of sugar to your coffee to sweeten it. If you originally used 500 mL of water to
make your coffee, what will be the resulting concentration of sugar (in g/L)?
6. How much water would you need to add to 3 g of sugar to make a solution with a
concentration of 400 mg/L?
7. What would be the concentration (in g/L) of a solution made by dissolving 20 g of chlorine in
12000 mL of water?
8. Determine the amount of water you would need to add to 10 g of KoolAid to make a solution
with a concentration of 6000 ppm.
9. The salt concentration of seawater is 35 000 ppm. What is this concentration in g/L?
10. If you had 500 mL of salt water (see question 9 for concentration), and you added 10 g of
salt to it, what would be the resulting concentration in g/L?
11. Determine the concentration (in ppm) of a solution prepared by mixing 4 mg of fluoride
with 500 mL of water.
12. What mass of potassium chloride would you need to add to 1.5 L of water in order to make
a solution with a concentration of 800 ppm?
13. You want to make a calcium chloride solution with a concentration of 3600 ppm. What
mass of calcium chloride would you need to add to 400 mL of water to make this solution?
Answers:
1.
2.
3.
4.
5.
20 g/L
800 mg
25000 ppm
13.5 g
10 g/L
6.
7.
8.
9.
10.
7.5 L
1.67 g/L
1.67 L
35 g/L
55 g/L
11. 8 ppm
12. 1200 mg or 1.2 g
13. 1440 mg or 1.44 g