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Chapter16 Solutions
16.1 Properties of Solutions
Chemistry
Today we are learning to:-
1. Understand what is meant by solubility
2. Identify factors that affect solubility of a substance
Types of Solutions
Solutions are a homogenous mixture of substances. Atoms, ions or molecules are
spread out evenly throughout another substance.
i. All three states of matter form solutions for example a solid may be
dissolved in another solid. Ex. Brass (zinc and copper alloy)
ii. Usually we think of liquids as forming solution. Ex. Salt/water solution
Some vocabulary you must know:
Solute: the substance that dissolves. Ex salt.
Solvent: the substance that does the dissolving. Ex. water.
Solution: the solute dissolved in the solvent forms this. Ex. Salt solution.
Solubility: describes how easily a solute will dissolve in a solvent
Soluble: it dissolves
Insoluble: it doesn’t dissolve
Types of Solutions
How do you know you have a solution?
i. Homogeneous mixture
ii. Light passes straight through (not dispersed)
iii. May be colored
iv. Does not settle on standing
v. Doesn’t separate out when filtered
Chapter 15&16 Solutions
16.1 Properties of Solutions
Exothermic and Endothermic Processes
17.1
Factors Affecting Solubility
1. The type of solvent and solute
A.Ionic solids and polar molecules will dissolve in polar solvents but not in non polar ones. Ex. in the ionic solid NaCl(s), Na+ ions are attracted to the negative pole of water molecules and Cl- ions to the positively charged pole of water molecules.
B.Nonpolar molecules will dissolve in nonpolar solvents but not in polar ones such as water Ex. Oils and fats are nonpolar. The will not dissolve in water (polar solvent) but will dissolve in gasoline (nonpolar solvent)
Like dissolves like
Exothermic and Endothermic Processes
17.1
Exothermic and Endothermic Processes
17.1
Factors Affecting Solubility
2. Temperature
Usually as temperature increases substances become more soluble in water.
• Exceptions to this rule include gases, which come out of solution as temperature increases.
Exothermic and Endothermic Processes
17.1
Factors Affecting Solubility
3. Pressure
Usually has no effect on solubility of solids or liquids.
• Solubility of gases increases as pressure increases.
• Ex. Soda water has a lot of carbon dioxide gas dissolved in it as it is under high pressure. When a can is opened the pressure in the can drops and the carbon dioxide escapes as bubbles
Now try review questions 1-12 on page 120 and 121
Exothermic and Endothermic Processes
17.1
Solubility Graphs
1. The type of solvent and solute
A.Ionic solids and polar molecules will dissolve in polar solvents but not in non polar ones. Ex. in the ionic solid NaCl(s), Na+ ions are attracted to the negative pole of water molecules and Cl- ions to the positively charged pole of water molecules.
B.Nonpolar molecules will dissolve in nonpolar solvents but not in polar ones such as water Ex. Oils and fats are nonpolar. The will not dissolve in water (polar solvent) but will dissolve in gasoline (nonpolar solvent)
Like dissolves like
Exothermic and Endothermic Processes
17.1
Solubility Graphs (Table G)
• Shows number of grams of substance that can be dissolved in 100g of water at a given temperature.
• The line shows the maximum amount of that substance that can dissolve at that temperature.
0 10 20 30 40 50 60 70 80 90 100
Solubility vs. Temperature for Solids
Sol
ubili
ty (
gram
s of
sol
ute/
100
g H
2O)
KI
KCl
20
10
30
40
50
60
70
80
90
110
120
130
140
100
NaNO3
KNO3
HCl NH4Cl
NH3
NaCl KClO3
SO2
gases
solids
Look at the solubility curve for potassium nitrate only
Exothermic and Endothermic Processes
17.1
Solubility Graphs (Table G)
0 10 20 30 40 50 60 70 80 90 100
Solubility vs. Temperature for Solids
Sol
ubili
ty (
gram
s of
sol
ute/
100
g H
2O)
20
10
30
40
50
60
70
80
90
110
120
130
140
100
KNO3
Where the temperature is 40C
Below the curve the solution is unsaturated. This means we could dissolve more KNO3
On the curve the solution is saturated. This means we are at the maximum mass of KNO3 that will dissolve at that temperature
Above the curve the solution is supersaturated. The solution is unstable. Addition of a single crystal will cause rapid crystalization
Exothermic and Endothermic Processes
17.1
Solubility Graphs (Table G)
0 10 20 30 40 50 60 70 80 90 100
Solubility vs. Temperature for Solids
Sol
ubili
ty (
gram
s of
sol
ute/
100
g H
2O)
20
10
30
40
50
60
70
80
90
110
120
130
140
100
KNO3
Where the mass of KNO3 is 60 g/100g H2O
Unsaturated solution cools
On the curve the solution is saturated. This means we are at the maximum mass of KNO3 that will dissolve at that temperature
The solution is supersaturated. The solution is unstable. Addition of a single crystal will cause rapid crystalization
Ex1:What substance has a solubility of 73 g/100 cm3 of water at a temperature of 90ºC ?
NH4Cl (ammonium chloride)
Ex2:At what temperature will potassium nitrate have a solubility of 95 g/100 cm3 ?
55ºC
Ex3:30 grams of potassium nitrate has been added to 100 cm3 of water at a temperature of 50ºC. How many additional grams of solute must be added in order to make it saturated?
From graph you can see that the solubility for potassium nitrate at 50ºC is 84 grams
So we need to add 84-30 = 54g of potassium nitrate.
Ex3:30 grams of potassium nitrate has been added to 100 cm3 of water at a temperature of 50ºC. How many additional grams of solute must be added in order to make it saturated?
Exothermic and Endothermic Processes
17.1
Now try review questions 13-23 on page 123
END OF SHOW
