Subjects
Grades
Concentration Calculations in g/L and %
Concept sheet | Science and Technology
Secondary
3-4
There are many ways to express concentration. The following sections focus on calculating concentration in |\text{g/L}| and percent (|\text{%}|). Practice questions and examples are included too.
Calculating Concentration in |\text{g/L}|
Concentration in |\text{g/L}| refers to the ratio of the mass of the dissolved solute to the given volume of the solution.
|C=\dfrac{m_{solute}}{V_{solution}}|
where
|C:| concentration in grams per litre |(\text{g/L})|
|m_{solute:}| mass of the solute in grams |(\text{g})|
|V_{solution:}| volume of the solution in litres |(\text{L})|
A mass of |100\ \text{mg}| of potassium nitrate |(\text{KNO}_3)| is dissolved in |0.800\ \text{L}| of water. What is the concentration of the solution in |\text{g/L}|?
See solution
Sodium hydroxide |(\text{NaOH})| is used to prepare |250\ \text{mL}| of a |2.00\ \text{g/L}| aqueous solution. What is the mass, in grams |(\text{g}),| of sodium hydroxide required to prepare the solution?
See solution
Concentration in g/L
Moments in the video:
- 00:00-Formula used to calculate concentration in g/L
- 00:33-Solving the problem to find concentration
- 00:36-Technically, chocolate milk is not a solution. It's not a homogeneous mixture, but rather a colloid. That said, the concept of concentration is easier to understand with delicious chocolate milk!
- 01:31-Solving the problem to find the mass of the solute
Calculating Concentration in Percent (|\text{%}|)
Percent concentration is the percentage of the amount of dissolved solute compared to the given amount of solution. The amount can refer to mass or volume.
There are three types of percent concentration:
-
mass percent, also called mass/mass percentage |(\text{% m/m}),|
-
volume percent, also called volume/volume percentage |(\text{% V/V}),|
-
mass per volume percent, also called mass/volume percentage |(\text{% m/V}).|
The following table summarizes the formulas and the context for using each one.
|
|
Mass percent |(\text{% m/m})| |
Volume percent |(\text{% V/V})| |
Mass per volume percent |(\text{% m/V})| |
|---|---|---|---|
|
Formula |
||C=\left(\dfrac{m_{solute}}{m_{solution}}\right)\times 100|| |
||C=\left(\dfrac{V_{solute}}{V_{solution}}\right)\times 100|| |
||C=\left(\dfrac{m_{solute}}{V_{solution}}\right)\times 100|| |
|
Notes |
|
A |\text{m/V}| percentage corresponds to the mass of the solute per |100\ \text{mL}| of solution. |
|
|
Context |
Mass percent concentration is generally used when both the solute and the solvent are solid. |
Volume percent concentration is generally used when both the solute and the solvent are liquid. |
Mass per volume percent concentration is generally used when the solute is solid and the solvent is liquid. |
Exercise
A metal block consists of |22.0\ \text{g}| of nickel |(\text{Ni})| and |84.0\ \text{g}| of zinc |(\text{Zn}).| What is the mass percent concentration of nickel in the metal block?
See solution
In a laboratory, sulphuric acid |(\text{H}_2 \text{SO}_4)| is used to prepare |125\ \text{mL}| of a |5.00\text{% V/V}| aqueous solution. How much sulphuric acid is required to prepare the solution?
See solution
The percent concentration of a solution is |2.5\text{% m/V}.| What is the concentration of the solution in grams per litre |(\text{g/L})|?
See solution
Percent Concentration
Moments in the video:
- 00:00-Percent concentration
- 00:26-Units of percent concentration
- 01:11-Calculating concentration using ratios
- 01:30-Units of solute and solvent
- 02:00-Example 1: concentration using ratios
- 02:14-Technically, chocolate milk is not a solution. It's not a homogeneous mixture, but rather a colloid. That said, the concept of concentration is easier to understand with delicious chocolate milk!
- 03:08-Example 2: concentration using the formula