1. Measuring concentration

2. Units of concentration
The units of concentration tell us the relative amount of solute dissolved in a solvent.
g/L or gL-1 (sometimes mg/L or mgL-1)
mol/L or molL-1 (sometimes labelled M)
Ppm (parts per million or ppb – parts per billion)
% concentrations

3. gL-1
This tells us how many grams of solute are dissolved in 1 litre of solution.
Concentration (gL-1) = mass of solute (g)
Volume of solution (L)
Eg 1. What is the concentration, in gL-1 of a solution containing 8.00g of sodium chloride in 500mL of solution?
Eg2. What is the concentration in gL-1 of a solution containing 5.00g of glucose in 250 mL of solution?

4. ppm
For solutions that have very low concentrations, parts per million, ppm, units are used.
ppm can be thought of as grams per grams or the mass in mg per kg
1 ppm = 1mg/kg = 1mg/L
Concentration (ppm) = mass of solute (mg)
mass of solution (kg)
Eg A sample of tap water is found to contain g of NaCl per 250.0g of solution. Calculate the concentration of NaCl in parts per million (ppm)

5. Molar (M) = molL-1 Concentration (molL-1) = amount of solute(mol)
volume of solution (L)
c = 𝑛 𝑉 or n = cV
Eg 1 Calculate the molar concentration of a solution that contains mol of KNO3 dissolved in 200mL of solution.
Eg 2 Calculate the concentration, in molL-1, of a solution that contains 4000mg of ethanoic acid (CH3COOH) dissolved in 100mL of solution.

6. % compositions %m/m = g in 100g of solution
What is the concentration, in %(m/m), of a 300g solution of KNO3 that contains 15 g of solute
%m/v = g in 100mL of solution
In 5.0mL dose of cold and flu medicine, there is 2.00mg of the active ingredient. What is the concentration of the chemical, in mgL-1 and %(m/v)?
% v/v = mL in 100mL of solution

7. Dilution
The process of adding more solvent to a solution is called dilution.
While the number of solute particles stays the same the concentration of the solution decreases.
We can use n=cV
add water

8. Dilution questions
Calculate the concentration of the solution formed when 10.0mL of water is added to 5.00mL of 1.2M HCl.
A laboratory technician wishes to produce 5.00L of 2.50M sulfuric acid from a stock bottle of 18.0M H2SO4.
What volume of the concentrated acid will be required?