1. Understanding dilutions

2. Sometimes we make up solutions by diluting a stronger solution that has already been made up. If the concentration of the original solution is accurately known, and volumetric glassware (pipettes and volumetric flasks) are used, then the concentration of the diluted solution can be calculated. Dilutions If the concentration of a diluted solution is determined experimentally, the reverse of this formula is used to find the concentration of the original solution:

3. What is the concentration of a citric acid solution prepared by taking 20.0 mL of 0.784 mol L –1 and diluting it to 250.0 mL?

4. What volume of 2.0 mol L –1 H 2 SO 4 should be used to make up 250.0 mL of 0.05 mol L –1 solution? Instead of plugging numbers into a formula, try using logic: 250 mL of 2.0 mol L –1 H 2 SO 4 in 250 mL = 2.0 mol L –1 125 mL of 2.0 mol L –1 H 2 SO 4 in 250 mL = 1.0 mol L –1 12.5 mL of 2.0 mol L –1 H 2 SO 4 in 250 mL = 0.1 mol L –1 6.25 mL of 2.0 mol L –1 H 2 SO 4 in 250 mL = 0.05 mol L –1

5. What volume of 2.0 mol L –1 H 2 SO 4 should be used to make up 250.0 mL of 0.05 mol L –1 solution? If you don't like logic, put the numbers into the formula and rearrange to find the pipette volume:

6. What is the concentration of sodium chloride if 20.0 mL of solution diluted to 100.0 mL has a concentration of 0.127 mol L –1.

7. If the solution has been diluted several times, just string the dilutions together: