1. Chapter 6: Solutions

2. This chapter will introduce the chemistry needed to understand:
Section 1: Solutions & electrolytes
Section 2: Concentrations of solutions
Section 3: Acidity & pH

3. Section 1—Solutions & Electrolytes

4. Dissolving Substances
Substances are dissolved by a process called hydration when the solvent is water
The solvent and solute need to break intermolecular forces within themselves- This requires ENERGY (ENDOTHERMIC)
New intermolecular forces are formed between the solvent and solute.- This releases ENERGY(EXOTHERMIC)
The solvent “carries off” the solute particles

5. Solution Formation
Endothermic
Exothermic
Endothermic

6. Dissolving Ionic Compounds+ - O H - +
Solute,Ionic compound
Solvent,water
Water molecules are polar and they are attracted to the charges of the ions in an ionic compound. - + -
When the intermolecular forces are stronger between the water and the ion than the intramolecular forces between the ions, the water carries away the ion. + - + - + -

7. Dissolving Ionic Compounds+ - O H - +
Ionic compound
water -
As more ions are “exposed” to the water after the outer ions were “carried off”, more ions can be “carried off” as well. + - + - + - + -

8. DRAW THIS IN THE BOX + - O H - +
Ionic compound
water + -
These free-floating ions in the solution allow electricity to be conducted - + - + - + -

9. Electrolytes
When there are free-floating charges in a solution then it can conduct electricity.
Substances that produce free-floating charges when dissolved in water are called electrolytes.

10. Dissolving Covalent Compounds: POLAR MOLECULES
Solvent, water (polar) + -
- +
Solute, sugar (polar)
Polar covalent molecules are formed in the same way—water forms intermolecular forces with the solute and “carries” the solute particles away.
- +
- +
- +

11. DRAW THIS IN THE BOX
Solvent, water (polar) + -
- +
Solute, sugar (polar)
However, the polar covalent molecules stay together and just separates from other solute molecules. NO charged ions form.
- +

12. Non-electrolytes
When molecules separate from other molecules, but free-floating charges are not produced, the solution cannot conduct electricity.
These are called
non-electrolytes

13. Types of Electrolytes Strong Electrolytes Weak Electrolytes
Non-Electrolytes
Soluble
Ionic compounds
Strong Acids & Bases
Insoluble
Ionic Compounds
Weak Acids & Bases
Covalent Compounds except for ACIDS & BASES
Almost all ions are separated when dissolved in water.
Only a few ions are separated when dissolved in water
No molecules separate—ions are not formed
Easily conducts electricity when dissolved in water
Conducts electricity slightly when dissolved in water
Does not conduct electricity at all when dissolved in water

14. Breaking up Electrolytes
Leave polyatomic ions in-tact (including the subscript within the polyatomic ion)
All subscripts not within a polyatomic ion become coefficients
Be sure to include charges on the dissociated ions!
Example:
Break up the following ionic compounds into their ions
KNO3
Ca(NO3)2
Na2CO3

15. Breaking up Electrolytes
Leave polyatomic ions in-tact (including the subscript within the polyatomic ion)
All subscripts not within a polyatomic ion become coefficients
Be sure to include charges on the dissociated ions!
Example:
Break up the following ionic compounds into their ions
KNO3
Ca(NO3)2
Na2CO3
 K+1 + NO3-1
 Ca NO3-1
 2 Na+1 + CO3-2

16. Section 2: Types of Solutions
A solution is made of two parts:
SOLUTE: the substance that is dissolved; usually in minority
SOLVENT: The substance that does the dissolving, usually in majority
When 2 substances dissolve in one another, they are SOLUBLE
If they cannot dissolve in one another, they are INSOLUBLE

17. Examples of Solutions SOLID-LIQUID LIQUID-SOLID GAS-LIQUID Salt Water
Dental Filling (Mercury in Silver)
SODA
(Carbon dioxide gas in water)

18. Examples of Solutions When 2 liquids dissolve in one another, they are
SOLID-SOLID
LIQUID-LIQUID
GAS-GAS
ALLOYS
(brass, bronze, sterling silver, steel)
Alcohol & water
Acetic acid in water(vinegar)
AIR
(Oxygen in Nitrogen gas)
When 2 liquids dissolve in one another, they are
MISCIBLE
If they cannot dissolve in one another, they are IMMISCIBLE.

19. Types of Solutions Unsaturated Saturated Super-Saturated
Has more solute dissolved than a saturated solution has at room temperature
No visual- need some background information
Not full- we can add solute to the solvent & it will dissolve
Visual-no solid on bottom
It’s “Full”- no more solute can be dissolved
Visual- solid can be seen at the bottom

20. Diagrams of Unsaturated,Saturated, & SuperSaturated Solutions

21. Diagrams of Unsaturated vs Saturated Solutions

23. A SUPERSATURATED SOLUTION
A supersaturated solution can be seeded. This is a solution at room temperature that has beyond the maximum amount of solid it can dissolve.

24. A SUPERSATURATED SOLUTION
Crystallization Begins.

25. A SUPERSATURATED SOLUTION
Crystallization Continues.

26. A SUPERSATURATED SOLUTION
A SuperSautrated solution is now saturated. This is also very exothermic!

27. Solubility of a Gas vs Liquid
In general,
the higher the temperature of a solution, more solid can be dissolved.
the higher the temperature of a solution, less gas can dissolve. Thermal Pollution!

28. Solubility of Gas vs Liquiud

29. Henry’s Law
As the pressure above a liquid increases, the solubility of a gas within a liquid will increase

30. Reading a Solubility Curve
Find the data point on the graph of the temperature and solubility of solute in solvent.
If it is below the line, it is UNSATURATED
IF it is on the line, it is SATURATED
If it is above the line, the difference between the point and the line is the extra amount that is sitting at the bottom.

31. Reading a Solubility Curve
Examples
What kind of solution occurs when 40g of KCl is dissolved in 100 g H2O at 60ºC?
What kind of solution occurs when 40g of KCl is dissolved in 100 g H2O at 40ºC?
What is the maximum amount of NaBr that can be dissolved in 100 g H2O at 60ºC?
unsaturated
saturated
120 g

32. Reading a Solubility Curve
Examples
4. What is the maximum amount of KNO3 that can be dissolved at 70ºC?
5. According to the diamond mark, How much of the KNO3 has been added to the water at 70ºC?
6. How much extra KNO3 is sitting at the bottom of the container at this temperature of 70ºC?
140g
160g
20g

33. Factors that Affect the Rate of Hydration
1. Temperature
2. Particle Size
3. Agitation (stirring)

34. Section 3: Concentration
A measure of the amount of solute in a given amount of solution
Qualitative Description:
Dilute: small amount of solute compared to solvent
Concentrated: large amount of solute compared to solvent
Concentrated
Dilute

35. Concentrated versus Dilute
solvent
solute
Lower concentration
Not as many solute (what’s being dissolved) particles
Higher concentration
More solute (what’s being dissolved) particles

36. Molarity: a quantitiative description of concentration
Molarity (M) is a concentration unit that uses moles of the solute instead of the mass of the solute
2M solution is 2 moles of solute dissolved in 1.0 L of solution
moles
Molarity X
Liters

38. Molarity Example Example:
If you dissolve 5.0 moles of NaCl in mL of water, what is the molarity?

39. Molarity Example 17 M NaCl Example:
If you dissolve 5.0 moles of NaCl in mL of water, what is the molarity?
Remember to change mL to L! mL of water = L
17 M NaCl

40. Molarity Example Example:
If you dissolve 12.0 g of NaCl in mL of water, what is the molarity?

41. Molarity Example = _______ mole NaCl 1.37 M NaCl
If you dissolve 12.0 g of NaCl in mL of water, what is the molarity? Na Cl 1
22.99 g/mole
35.45 g/mole  = +
58.44 g/mole
1 mole NaCl molecules = g
12.0 g NaCl 1
mole NaCl
= _______ mole NaCl
0.205
58.44
g NaCl
Remember to change mL to L! mL of water = L
1.37 M NaCl

42. Molarity Example Example:
How many grams of CaCl2 would be needed to make 25.0 ml of a 2.5M solution?

43. Molarity Example = 6.9 grams CaCl2 .0625 moles NaCl
How many grams of CaCl2 would be needed to make 25.0 ml of a 2.5M solution? Ca Cl 1 2
40.01 g/mole
35.45 g/mole  =
40.08 g/mole
70.90 g/mole +
g/mole
1 mole CaCl2 = g
.063 mol CaCl2
110.98
g CaCl2
= grams CaCl2
1 mol
CaCl2
Remember to change mL to L! 25 mL of water = L
.0625 moles NaCl

44. How to Make a Solution Make 500. 0 ml of a 0
How to Make a Solution Make ml of a 0.12 M solution of CoCl22H2O
1st: Convert your moles of solute to grams.
.12 M x .500L = .060 moles solute
.060 moles x g/1mol = g
(10. g)
2nd : Add solute amount to a volumetric flask.
Add 10.0 g cobalt chloride to flask
3rd : Add enough solvent to make the required amount of solution and stir.
In this case, the solvent is ethanol. Add slowly until 500 ml of solution is reached.

45. What Not to Do! Never add the solvent first!

46. Dilution: A technique used to make a dilute solution from a Concentrated Solution
= mol
.10 L
= .050 M I2
= mol
.50 L
= .010 M I2

47. How to Calculate a Dilution
M1V1= M2V2
moles1 = moles2
M1V1 = original(stock) concentration & volume
M2V2 = new concentration & volume
You do not have to change your volume to liters!
Example:
What is the molarity of a new solution if you diluted ml of 3.0M HCl to ml?

48. Example:. What is the molarity of a new solution if you diluted 100
Example: What is the molarity of a new solution if you diluted ml of 3.0 M HCl to ml?
M1V1= M2V2 (3.0M)(100.0ml) = (X)(250.0 ml) Mml= 250.0ml x ml 250.0ml X= 1.2 M

49. Add 875 ml of water to 375 ml to make 1250 ml.
Example: What volume would need to be added to dilute a 375 ml of a 5.0 M to 1.5 M?
M1V1= M2V2
(5.0M)(375ml) = (X)(1.5M)
1875 Mml= 1.5M x
1.5 M M
X= 1250 ml
Add 875 ml of water to 375 ml to make 1250 ml.