Solutions, Suspensions Colloids

Solutions Appears to be a single substance

but really two or more substances dissolved in a solvent and evenly distributed

Very small particles that never settle out

Homogeneous

Examples of Solutions Alloys – solid solutions of metals or

non-metals dissolved in metals Iced tea, salt water, soda, gasoline

Solute versus Solvent A solute is the substance in a solution

that gets dissolved A solvent is the substance in a solution

that does the dissolving If something is soluble, the solute can

be dissolved in a particular solvent If something is insoluble, the solute will

not be dissolved in a particular solvent Solutes can be soluble in some solvents

but insoluble in others

Concentration The comparison of solute to

solvent When there is not a lot of solute

compared to solvent, the solution is dilute

When there is a lot of solute compared to solvent, the solution is concentrated

Saturated Solutions Saturated solution – contains all of

the solute it can hold at a given temperature. If you add even one more molecule of

the solute, it will fall out of solution and rest on the bottom

Unsaturated Solutions Contains less solute than it can

hold at a given temperature Can add more solute and it wont fall

out of the solution

Supersaturated Solution Solution that holds more than it

usually would at a given temperature

Solubility The amount of solute needed to make a

saturated solution in a given solvent at a given temperature

For solid solute in liquid solvent – solubility rises as temperature rises.

For gas solute in a liquid solvent – solubility lowers as temperature risesex – soda goes flat at warm temperatures

Solubility Table

LeMay Jr, Beall, Robblee, Brower, Chemistry Connections to Our Changing World , 1996, page 517 images.hboys2011.multiply.multiplycontent.com/.../SOLUBILITY%20CURVE%202.ppt?... 0 10 20 30 40 50 60 70 80 90 100

Solubility vs. Temperature for Solids

Solu

bili

ty (

gra

ms

of

solu

te/1

00

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

How to determine the solubility of a given substance?

• Find out the mass of solute needed to make a saturated solution in 100 cm3 of water for a specific temperature(referred to as the solubility).

• This is repeated for each of the temperatures from 0ºC to 100ºC. The data is then plotted on a temperature/solubility graph,and the points are connected. These connected points are called a solubility curve.

How to use a solubility graph?

A. IDENTIFYING A SUBSTANCE ( given the solubility in g/100 cm3 of water and the temperature)

• Look for the intersection of the solubility and temperature.

What substance has a solubility of 90 g/100 cm3 of water at a temperature of 25ºC ?

Example:

Example:

What substance has a solubility of 200 g/100 cm3 of water at a temperature of 90ºC ?

B. Look for the temperature or solubility

•Locate the solubility curve needed and see for a given temperature, which solubility it lines up with and visa versa.

• What is the solubility of potassium nitrate at 80ºC ?

At what temperature will sodium nitrate have a solubility

of95 g/100 cm3 ?

At what temperature will potassium

iodidehave a solubility of 230 g/100

cm3 ?

What is the solubility of sodium chloride at 25ºC in 150 cm3 of water ?

• From the solubility graph we see that sodium chlorides solubility is 36 g.

C. Determine if a solution is saturated,unsaturated,or supersaturated.

• If the solubility for a given substance places it anywhere on it's solubility curve it is saturated.• If it lies above the solubility curve, then it's

supersaturated,• If it lies below the solubility curve it's an

unsaturated solution. Remember though, if the volume of water isn't 100 cm3 to use a proportion first as shown above.

To

Sol.

To

Sol.

Solids dissolved in liquids Gases dissolved in liquids

As To , solubility As To , solubility

Sometimes you'll need to determine how much additional solute needs to be added to a unsaturated solution in order to make it saturated.

For example,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 the graph you can see that the solubility for potassium nitrate at 50ºC is 84 grams

If there are already 30 grams of solute in the solution, all you need to get to 84 grams is 54 more grams

( 84g-30g )

Classify as unsaturated, saturated, or supersaturated.

per100

gH2O

80 g NaNO3 @ 30oC

45 g KCl @ 60oC

50 g NH3 @ 10oC

70 g NH4Cl @ 70oC

=unsaturated

=saturated

=unsaturated

=supersaturated

0 10 20 30 40 50 60 70 80 90 100

Solubility vs. Temperature for Solids

Solu

bili

ty (

gra

ms

of

solu

te/1

00

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

LeMay Jr, Beall, Robblee, Brower, Chemistry Connections to Our Changing World , 1996, page 517 images.hboys2011.multiply.multiplycontent.com/.../SOLUBILITY%20CURVE%202.ppt?...

Methods to speed up dissolving Crushing a solute increases the surface area of

the solute allowing more solvent to surround it thus dissolving it faster Ex. Putting butter in macaroni and cheese

Heating a solution increases the energy of the molecules making them move more quickly thus spreading the solute throughout the solvent and speeding up the rate at which the solute dissolves Ex- cooking iced tea

Mixing has the same effect as heating does Ex- making chocolate milk

Suspensions A suspension is a mixture in which

particles of material are dispersed throughout a liquid or gas and are large enough to settle out

The particles are insoluble Heterogeneous mixtures Ex snow globe

Colloids Have properties of both solutions and

suspensions Particles in a colloid are much smaller than

particles in a suspension Colloids have the same definition as

suspensions in that a colloid is a mixture in which particles of material are dispersed throughout a liquid or gas, but the particles of a colloid are not large enough to settle out

Particles in a colloid scatter light Ex milk, fog, jello