solubility

SOLUBILITY

Let’s Review some vocabulary!

solubility: The ability to dissolve a substance in water.

solute: The substance being dissolved.

solvent: The substance that the solute is being dissolved in.

Water is considered the universal solvent! Why?

solution: A mixture made of solute(s) and a solvent.

Solutions

Some solutions are good conductors of electricity.

To understand conductivity of solutions we need to review covalent vs. ionic bonds:

Conductivity of Solutions

• Ionic bonds tend to break up in water, covalent bonds don't.

• This is b/c the charged ions are attracted to the opposite partial charges on the water molecules. So the ionic compound is pulled apart in the water!!!

• When the ionic bonds break, they leave the ions floating around in the water as charged particles. That's important…

Conductivity of Solutions

• It’s important b/c electricity is carried by charged particles. So, a good conductor of electricity would be a sodium ion, Na+, or a chlorine ion, Cl-. (See where this is going?)

• Covalent bonds do not have charged particles.

• So solutions that have an ionic compound as a solute will conduct electricity well!!!

Solubility Curves (Graphs)

Solubility varies from one substance to the next.

Therefore, we have solubility curves… graphs of solutes regarding the amount that will dissolve in a certain amount of solvent.

Solubility Curve

0

20

40

60

80

100

120

140

160

180

200

0 10 20 30 40 50 60 70 80 90 100

Temperature of Solvent oC

So

lute

(g

) d

isso

lved

in

100

ml

of

wat

er NaCl

KCl

KNO3

How much KNO3 can be dissolved at 70oC in 100 cc of water?

120 g

Reading a Solubility Curve

Where the solutes cross they are equally soluble at that temperature.

(Remember: Temp. is on the X-AXIS

Amount of Solute dissolved is on the Y-AXIS)

Solubility Curve

0

20

40

60

80

100

120

140

160

180

200

0 10 20 30 40 50 60 70 80 90 100

Temperature of Solvent oC

So

lute

(g

) d

isso

lved

in

100m

l o

f

wate

r NaCl

KCl

KNO3

At what temperature are the solutes equally soluble?

28 oC (If you said 38, you were reading the wrong axis!)

Solubility Curve

0

20

40

60

80

100

120

140

160

180

200

0 10 20 30 40 50 60 70 80 90 100

Temperature of Solvent oC

So

lute

(g

) d

isso

lved

in

100m

l o

f

wate

r NaCl

KCl

KNO3

How much KNO3 can be dissolved at 50oC in 100 cc of water?

About 75 g (Don’t forget units!!!)

Solubility Curve

0

20

40

60

80

100

120

140

160

180

200

0 10 20 30 40 50 60 70 80 90 100

Temperature of Solvent oC

So

lute

(g

) d

isso

lved

in

100m

l o

f

wate

r

NaCl

KCl

KNO3

Q: At what temperature can 52 g of KCl be dissolved?

80 o C (Don’t forget units!!!)

Solubility Curve

0

20

40

60

80

100

120

140

160

180

200

0 10 20 30 40 50 60 70 80 90 100

Temperature of Solvent oC

So

lute

(g

) d

isso

lved

in

100m

l o

f

wate

r

NaCl

KCl

KNO3

Q: How much NaCl can be dissolved at 60oC?

39 g

Reading a Solubility Curve For Gases

• The solubility curve for gasesare the opposite of the solubility curve for solids.

• The solubility of a gas decreases as the temperature increases.

Solid graph

Gas graph

Solubility Curve w/ Gases

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80

100

120

140

160

180

200

0 10 20 30 40 50 60 70 80 90 100

Temperature of Solvent oC

So

lute

(g

) d

isso

lved

in

100

ml

of

wat

er

NH3 (gas)

KCl

KNO3

HCl (gas)

Which substances on the graph are gases?

NH3 and HCl

Solubility Curve w/ Gases

0

20

40

60

80

100

120

140

160

180

200

0 10 20 30 40 50 60 70 80 90 100

Temperature of Solvent oC

So

lute

(g

) d

isso

lved

in

100

ml

of

wat

er

NH3 (gas)

KCl

KNO3

HCl (gas)

Q: How much NH3 can be dissolved at 65oC?

20 g

Solubility Curve w/ Gases

0

20

40

60

80

100

120

140

160

180

200

0 10 20 30 40 50 60 70 80 90 100

Temperature of Solvent oC

So

lute

(g

) d

isso

lved

in

100

ml

of

wat

er

NH3 (gas)

KCl

KNO3

HCl (gas)

At what temperature can 60 g of HCl be dissolved?

45 oC

Saturated SolutionsSaturation is when something has dissolved in a solution and no more of it will dissolve under normal circumstances. It has reached equilibrium.

Unsaturated Solutions

Unsaturated is just before the equilibrium is reached, so you can keep dissolving the substance into the solution.

Supersaturated Solutions

• Supersaturated is when you change the conditions so that you can dissolve more of the substance into the solution than it normally would.

• If the solution is brought back under normal conditions, it will spit back out the substance. (Coca-cola is an example of a super saturated solution of CO2, when a bottle is opened it will attempt to reach equilibrium again by bubbling and fizzing. When it does reach equilibrium it becomes flat)

• Another example is Rock Candy

Solubility Curve

0

20

40

60

80

100

120

140

160

180

200

0 10 20 30 40 50 60 70 80 90 100

Temperature of Solvent oC

So

lute

(g

) d

isso

lved

in

100m

l o

f

wate

r NaCl

KCl

KNO3

Saturated

Unsaturated

Super saturated

Factors that Affect Solubility

There are three main factors that will cause the rate of solubility (how fast a solute dissolves) to increase.

Can you guess what they might be? 1. Stirring2. Heating the solution3. Increasing the surface area of the solute

1. A mixture made of solute and solvent is called a:

Solu

tion

Solv

ent

Sat

urate

d

Solu

bility

65%

0%

15%20%

A. SolutionB. SolventC. Saturated D. Solubility

2. Ionic bonds break up in water to form a conductive

solution

Tru

e

Fal

se

20%

80%A. TrueB. False

3. Gases follow the same solubility curve as solids.

Tru

e

Fal

se

95%

5%

A. TrueB. False

4. This is when you change the conditions so that you can dissolve more of a substance into the solution than you normally could.

Solu

tion

Solu

bility

Sat

urate

d

Unsa

tura

ted

Super

sat

urate

d

0%5%

90%

0%5%

A. SolutionB. SolubilityC. SaturatedD. UnsaturatedE. Super saturated

5. This is the substance that is being dissolved in a solvent.

Solu

te

Solu

tion

Solu

bility

Sat

urate

d

100%

0%0%0%

A. SoluteB. SolutionC. SolubilityD. Saturated

6. At what temperature is Compound X and Y equally soluble?

45 170 39

They

are

not.

5%0%

95%

0%

A. 45B. 170C. 39D. They

are not.

7. Which compound is considered unsaturated?

X Y

60%

40%

A. XB. Y

8. The substance that the solute is being dissolved in is:

Solu

tion

Solv

ent

Sat

urate

d

Solu

bility

20%

5%5%

70%A. SolutionB. SolventC. SaturatedD. Solubility

9.How many grams of compound X is dissolved at 80 degrees ?

140 70 12

0 80

0%5%

95%

0%

A. 140B. 70C. 120D. 80

10. At what temperature is 80g of compound Y dissolved?

80 60 100 40

5%0%

85%

10%

A. 80B. 60C. 100D. 40