Dilutions
When you take some frozen concentrated orange juice, put it into a pitcher, then add some water, you have performed a dilution. When putting antifreeze into a car's radiator, the antifreeze must be mixed with water, or diluted. A can of condensed soup must be diluted with water. Many everyday processes require us to dilute the original solution.
Chemists will often store solutions in a more concentrated form to save on storage space and the ease of making new solutions. These types of solutions are called stock solutions. Virtually an infinite number of solutions of varying concentrations can be made from a single stock solution, simply by adding more solvent.
To dilute a solution means to add more solvent without adding more solute. Since the number of moles of solute remains the same (since no more solute is added), calculations of new concentrations becomes easier.
To dilute a solution means to add more solvent without adding more solute. Since the number of moles of solute remains the same (since no more solute is added), calculations of new concentrations becomes easier.
This video demonstrates how to calculate concentrations and volumes when doing dilutions.
After watching the video practice calculations by doing the questions below. (answers are provided in the brackets)
After watching the video practice calculations by doing the questions below. (answers are provided in the brackets)
1. If 500. mL of water is added to 300. mL of a 0.100 mol/L solution of NaCl, what is the new concentration?
(0.0375 mol/L)
2. What is the concentration of the stock solution if 50.0 mL of the solution is diluted to make 220. mL of a 0.400 mol/L solution?
(1.76 mol/L)
3. How much water must be added to 25.0 mL of a 1.00 mol/L stock solution of NaOH to make a 0.100 mol/L solution?
(0.225 L or 225 mL)
(0.0375 mol/L)
2. What is the concentration of the stock solution if 50.0 mL of the solution is diluted to make 220. mL of a 0.400 mol/L solution?
(1.76 mol/L)
3. How much water must be added to 25.0 mL of a 1.00 mol/L stock solution of NaOH to make a 0.100 mol/L solution?
(0.225 L or 225 mL)
Mixing Solutions with the Same Solute
Open and take notes on mixing solutions with the same solute.
Once you are finished practice by completing the question below. (answer is in brackets) |
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1. 450.0 mL of 2.40 mol/L H2SO4 is mixed with 375 mL of 8.20 mol/L H2SO4. What is the new concentration?
(5.04 mol/L)
Preparing a Dilution
Preparing a diluted solution is very similar to preparing a solution, except there is no solute to mass.
To prepare a diluted solution:
i. Determine the volume of stock solution needed.
ii. Add the stock solution to a volumetric flask.
iii. Add water to the volumetric flask up to the mark and mix.
To prepare a diluted solution:
i. Determine the volume of stock solution needed.
ii. Add the stock solution to a volumetric flask.
iii. Add water to the volumetric flask up to the mark and mix.