1. Solutions Unit 13

2.
Day One

3. Solutions Homogeneous mixtures.
Composition may vary from one sample to another
Appears to be one substance, though really contains multiple materials.
Most homogeneous materials we encounter are actually solutions.
E.g., air and lake water.
Tro's Introductory Chemistry, Chapter 13

4. SOLUTIONS Consists of two parts Solute
The substance that is being dissolved
Solvent
The substance that is “DOING” the dissolving
Universal Solvent  water
Solutions in which the solvent is water are called aqueous solutions.

5. SOLUTIONS Must fit three criteria
Combination of two or more pure substances
Must be able to vary in concentration
Parts must be indistinguishable

6. Common Types of Solution
Solution phase
Solute phase
Solvent phase
Example
Gaseous solutions
Gas
Air (mostly N2 and O2)
Liquid solutions
Liquid
Solid
Soda (CO2 in H2O)
Vodka (C2H5OH in H2O)
Seawater (NaCl in H2O)
Solid solutions
Brass (Zn in Cu)
Tro's Introductory Chemistry, Chapter 13

7. How do we make solutions?
Remember there are two parts to a solution
Solute: stuff that is dissolving
Solvent: stuff “doing” the dissolving
When you talk about solutions you must talk about dissolving and solubility

8. What is solubility? Solubility :
Amount of a substance to dissolve into another at a given temperature and pressure
Not all substances are SOLUBLE!!!
Meaning they WILL NOT dissolve
How do I know what will be soluble?
RULE: “Like dissolves Like”

9. Does temperature affect solubility?
Solubility usually increases as temperature increases
Lets look at an example! Think about Hot tea!!

10. Saturation of Solutions
We can talk about saturation of solution in three ways!!
Saturated: a solution that cannot dissolve any more solute
Unsaturated: a solution that contains less solute than a saturated solution its able to dissolve more solute
Supersaturated: a solution holding more dissolved solute than what its supposed to hold

11. Supersaturated Solution
A supersaturated solution has more dissolved solute than
the solvent can hold. When disturbed, all the solute above
the saturation level comes out of solution.
Tro's Introductory Chemistry, Chapter 13

12. Adding Solute to various Solutions
Unsaturated
Saturated
Supersaturated
Tro's Introductory Chemistry, Chapter 13

13. Solubility and Temperature
The solubility of the solute in the solvent depends on the temperature.
Higher temperature = Higher solubility of solid in liquid.
Lower temperature = Higher solubility of gas in liquid.

14. Expressing Amounts with Solutions (A.K.A. CONCENTRATION)
Molarity (M)
Molality (m)
Mole Fraction (X)
Percent Composition or pph (% or pph)

15. Mole Fraction (X) X = moles solute/ total moles solution
What is the mole fraction in a solution that contains 2.2 moles of sugar and 250 mL of water?

16. Percent Composition (%) or parts per hundred (pph)
% = grams solute / total grams of solution
What is the percent composition of salt in a solution that contains 15 grams of salt and 25 grams of water?

17. Practice—Calculate the Mass Percent of a Solution that Has 10
Practice—Calculate the Mass Percent of a Solution that Has 10.0 g of I2 Dissolved in g of Ethanol.
Tro's Introductory Chemistry, Chapter 13

18. Practice—Milk Is 4. 5% by Mass Lactose
Practice—Milk Is 4.5% by Mass Lactose. Determine the Mass of Lactose in 175 g of Milk.
Tro's Introductory Chemistry, Chapter 13