1. Solutions

2. What is a solution? A homogenous mixture:
Composed of at least two different substances that can be separated using a physical technique.
The substances cannot be distinguished.
Homogenous mixtures are composed of a:
Solute, (substance which is dissolved).
Solvent, (liquid which dissolves the solute).
When you mix a solute and a solvent, two things can happen:
The solute dissolves and separates in the solvent.
The solute does not dissolve and forms a precipitate.

3. Common Solutions Solution can exist in any state of matter. Tap water
Water is the solvent, salt is the solute.
Air
Nitrogen is the solvent, oxygen, water vapour, carbon dioxide are solutes.
Brass
Copper is the solvent, zinc is the solute.
Aqueous solutions are those in which the solvent is water.

4. Key Things to Remember
Solvent → Liquid doing the dissolving Solute → Substance being dissolved Solution → Combination of the solvent and the solute together. Example: Water and koolaid. Water is solvent, koolaid is solute, the solution is your drink.

5. Precipitates Precipitates can sometimes form within a solution.
Definition: formation of a solid in a solution.
Can form due to many things: (Key ones you need to know)
Solute you are trying to dissolve in solvent is insoluble (can’t dissolve).
Sand, oil, etc. are insoluble.
Too much of a soluble solute is introduced to a solvent and the solution becomes supersaturated.
Definition: solution that has more of a dissolved solute that can de dissolved by the solvent.

6. Things which ↑ or ↓ concentration
Definition: proportion of solute to solvent in a solution.
Things which ↑ or ↓ concentration
Dilution → adding water to solution = ↓ concentration.
Dissolution → adding solute to solution = ↑ concentration.
Evaporation → removing solvent from solution = ↑ concentration.
Concentration can be expressed in many ways.

7. Concentration Where C = concentration of solution
Formula:
C = m/V
Where C = concentration of solution
m = mass of solute (in g)
V = volume of solution (in L or mL)
Units for concentration:
g/L and g/mL are most common.
When concentration is given as a percentage:
%m/V % V/V % m/m

8. Recall on Converting Units
Multiply by 1000
-Going from bigger unit to smaller
Multiply by 1000
-Going from bigger unit to smaller kg g mg
Divide by 1000
-Going from smaller unit to bigger
Divide by 1000
-Going from smaller unit to bigger

9. Recall on Converting Units
Multiply by 1000
-Going from bigger unit to smaller L mL
Divide by 1000
-Going from smaller unit to bigger

10. Concentration Example #1
What is the concentration of a lemonade when 18 g of powder are dissolved in 10 L of the solution? m = 18 g V = 10 L C = 18 g/10 L → C = 1.8g/L

11. Concentration Example #2
What is the concentration of Ms. Maither’s coffee if there are 154 mg of caffeine dissolved in the solution in a 354 mL travel mug? m = 154 mg → need to convert to g → m = g V = 354 mL → need to convert to L → V = L C = g/0.354 L → C = 0.43 g/L

12. Concentration Example #3
What is the mass of salt present in 30 mL of saltwater with a concentration of 2.5%? C = 2.5%→ convert to fraction → C = 2.5/100 m = ? V = 30 mL 2.5/100 = m/30 → cross multiply m = (2.5 x 30)/100 → m = 0.75 g

13. Concentration Example #4
Place the following solutions in order from highest concentration to lowest concentration.
4 g/2800 mL
8.1%
167 mg/10 mL
15849 mg/14879 mL
2 g/L
Put everything in the same unit! Suggestion, convert everything to g/L.

14. …
g/L

15. Parts Per Million (ppm)
Unit of concentration used when the solute is much, much smaller than the amount of the solution.
In an aqueous solution, 1 ppm is equal to about 1 mg of solute in 1 L of solution.
1 ppm = 1 g/1000 L or mg/L
(When the solution is solid)