Unit 12 Solutions- Page 1 of 14

Unit 12 Chemistry– Solutions and Colligative Properties

Quiz Date: Test Date:

FORMULAS/VOCABULARY:

1 Molarity 2 freezing point depression 3 boiling point elevation 4 solute

5 solvent 6 alloy 7 solution 8 saturated 9 unsaturated

10 electrolytes 11 colligative property 12 net ionic equation 13 dilute solution

14 concentrated solution 15 nonelectrolytes 16 precipitate

OBJECTIVES:

Be able to describe the makeup of a solution.

Be able to identify electrolytes.

Be able to apply the formula for molarity

Be able to describe colligative properties.

Be able to read a solubility graph

Be able to read a table of solubility rules.

Using a table of solubility rules, be able to write net ionic equations.

From the Chemistry Reference Tables Packet (Do Not Memorize!):

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Chapter 13 - Solutions Read pages 395-410. Fill in the following worksheet:

Remember solutions are __________________ mixtures (look the same throughout) that can have

varying compositions. Most solutions (but not all) are made of solids dissolved in liquids. The part of

the solution that is dissolved is called the _______________________ and the substance it is dissolved into

(the dissolving medium) is called the _____________________________; the most common one is water

(sometimes called the universal solvent!). Because water is polar it is attracted to ions and other

polar molecules. For example when salt is placed in water its ions are pulled apart by the polarity of

the water. When ionic substances are dissolved in water they become solutions made up of

individual ions. Salt water is actually made up of sodium ions and chloride ions. See pics below:

Like substances will dissolve like substances when making solutions; so two polar substances or two

nonpolar substances will dissolve each other. If two substances will dissolve in each other they are

called _____________or miscible_. Not all solutions are solids in liquids. You can make solutions of two

metals (solids); these solutions are called alloys. An example is bronze, which is a solution of copper

and tin. You can also have gas dissolved in a liquid for example: ___________________ or a liquid

dissolved in a gas for example_______________________.

A substance that dissolves in water to produce ions and gives a solution that conducts a current is

called an ____________________________ and an example is_________________________. A substance

that dissolves in water and doesn’t conduct a current (because it doesn’t form ions) is called a

_____________________________ and an example is __________________________________.

Three ways to increase the rate of dissolving are:

1.

2.

3.

A solution where the undissolved substance is holding the maximum amount of solute is called a

_____________________________ solution. A solution with less than the saturated amount is

called__________________________________ and more than the saturated amount is a

_____________________________ solution. These are usually formed by heating a saturated solution and

then adding more solute.

The rate of dissolving gases in solution depends on pressure. Higher pressure allows more gas to be

dissolved in a liquid, this is based on Henry’s law. This is applied in dissolved carbon dioxide in soda

pop at high pressures. The release of these bubbles when your pop is opened is called

effervescence. Dissolved nitrogen gas in blood can affect scuba divers. If divers come up too fast,

the drop in pressure can cause N2 gas build ups which lead to the bends (which can be fatal).

Most solids increase in solubility with an increase in ________________________________________ due to

an increase in kinetic energy.

Unit 12 Solutions- Page 3 of 14

Label the pictures to the left as unsaturated

solution, saturated solution or supersaturated

solution.

Solutions and solubility

Solutions are ________________________________________________ mixtures in a single phase.

Solubility depends on: the nature of solute-solvent attraction , temperature and (for gases only)

pressure – think back to our phase diagrams

1) The nature of solute-solvent attraction: In order for a solute to be soluble in a particular solvent,

three things need to be considered. First, the intermolecular forces holding the solvent

molecules together must be broken to make room for the solute.

This requires energy (bond breaking always takes energy). Second, the intermolecular forces

holding the solute together must be broken. Again, this requires energy. Finally, the solute and

solvent particles must surround each other. This releases energy (bond formation or particle

interaction gives off energy), and is called solvation energy or hydration (when water is

involved) energy. If the energy needed in the first two steps is not too great and the solvation

energy is sufficiently large, the overall energy will be negative and a solution will be formed.

Based on solute-solvent attraction generally: ________________________

_____________________________________________ when making solutions; so two polar

substances or two nonpolar substances will dissolve each other.

A material is ________________________________________________________________________

General solubility guidelines:

-Polar molecules : _____________________________________________________________________

-Nonpolar molecules:_____________________________________________________________________

Extra info: Alcohols ______________________________________________________________________

Using the above 1. Determine if substance is ionic or covalent polar/ covalent nonpolar 2. X if

soluble in each other

SOLUTES

(ionic OR polar or

nonpolar) Write I,P or

NP

SOLVENTS (determine if they are polar or nonpolar first)

Water CCl4 HCl

__________ ______________

__________________

NaCl

I2

HBr

KNO3

CH4

2) Temperature: Generally higher temp lead to higher solubility due to an increase in kinetic

energy (exception is gases). Solubility curves are used to illustrate the relationship between

solubility and temperature – see solubility curve practice at the end of the packet.

Unit 12 Solutions- Page 4 of 14

Notes on Concentration Units

Solute = Dilute =

Solvent = Concentrated =

Solutions =

Molarity - M A way to measure solution concentration. It’s the most common chemistry

concentration unit.

Example1: What’s the molarity of 250ml of solution that has 12.7g of lithium bromide?

You try: Calculate the molarity of 450ml of solution that has 32g of sodium sulfate.

Example 2: how many grams of solute are required to make 500. ml of a .32 M solution of

lithium bromide and water?

YT: How many g of solute are needed to make 250ml of .5M solution of sodium sulfate

Molarity by dilution-(often done for acids & bases –we will cover in a few weeks!:

If you are given a solution and you are diluting it – you can calculate the new concentration

using this relationship: M1V1 = M2V2

Example: How much 12 M HCl is required to prepare 300 ml of a 5.0 M solution?

You try: To what volume should 35 ml of 15 M nitric acid be diluted to prepare a 6 M solution?

Unit 12 Solutions- Page 5 of 14

Unit 12 Solutions- Page 6 of 14

Unit 12 Solutions- Page 7 of 14

Solubility Rules:

Answer the following questions in the space provided.

1. Use your solubility rules to determine if the following substances are soluble-Yes or insoluble-NO in

water.

a. NaC2H3O2 d. AgCl g. NaCl j. HNO3

b. Li2SO4 e. K3PO4 h PbI2

c. Barium hydroxide f. CaCO3 i. MgBr2

Practice Writing Dissolution of Solids Equations:

Write the net ionic equation for the dissolution of the following compounds.

Sample: BaCl2 (s) Ba+2(aq) + 2Cl-1(aq)

a. Na3PO4 (s) c. CaI2 (s)

b. H2SO4 (s) d. Mg(NO3)2 (s)

Net Ionic Equations:

Steps for writing a net ionic equation

1. Write a balanced equation.

2. Use your solubility rules to determine solubility and break soluble compounds into ions (with

charges!). Leave insoluble compounds together without any charges!

3. Cancel out spectator ions – if everything cancels write no net reaction.

4. Write the final equation – include state symbols!

Example 1 (demo) AgNO3 + MgCl2

(a draw a picture!)

Example 2: K2S + Al(NO3)3

You try: HNO3 + Ba(OH)2

Unit 12 Solutions- Page 8 of 14

Solubility Rules and Net Ionic Equations Worksheet

Write net ionic equations for the following reactions:

1. Ba(NO3)2 + Na2CO3 BaCO3 + 2 NaNO3

2. sodium hydroxide + zinc nitrate sodium nitrate + zinc hydroxide

3. BaCl2 + Na2SO4

4. Silver nitrate and calcium bromide

5. sulfuric acid (H2SO4) and sodium chloride produce hydrochloric acid (HCl) and sodium sulfate

6. LiOH + H2S

7. aluminum chloride and iron (III) nitrate

8. ammonium chloride + lead (II) nitrate

9. rubidium carbonate + strontium acetate

Unit 12 Solutions- Page 9 of 14

Electrolytes, Nonelectrolytes and Colligative Properties

Electrolytes vs Nonelectrolytes

Exs:____________________ Exs: ______________________

ELECTROLYTES Worksheet

Compound Electrolyte Nonelectrolyte

NaCl

HCl

C6H12O6 (sugar)

NaOH

CO2

H2O

H2SO4

What is a colligative property? Depends on the concentration of a solution but not on the identity of

the solute.

Electrolytes have a greater effect on colligative properties than do nonelectrolytes.

B/c electrolytes actually dissolve into more particles than do nonelectrolytes:

Examples

SUGAR Non E SALT E

5 molecules dissolved in water 5 atoms in water makes=

makes= ________ Na+ and _______ Cl-

__________ particles of sugar a total of ______________ particles

4 Colligative properties:

A. Vapor pressure lowering

Unit 12 Solutions- Page 10 of 14

B. Freezing point depression: Solutions have a ____________ freezing point than pure water.

Ex?

C. Boiling point elevation: solutions have a ________________ boiling point than pure water.

Example?

Unit 12 Solutions- Page 11 of 14

Solubility Graph Worksheet extra practice

1. Why do the temperatures on the graph only go from 0º C to 100º C ?

2. Which substance is most soluble at 20º C ?

3. Which three substances have the same solubility at 26º C ?

4.Which substance’s solubility changes the most from 0º C to 100º C ?

5.Which substance’s solubility changes the least from 0º C to 100º C ?

6. What is the solubility of potassium nitrate at 40º C ?

7. At what temp does potassium chloride have a solubility of 50 g/ 100 ml water ?

8. You have a solution of sodium nitrate containing 40 g at 35º C. Is the solution saturated,

unsaturated, or supersaturated ?

9. You have a solution of potassium chlorate containing 10 g at 65º C. How many additional grams of

solute must be added to it, to make the solution saturated?

Unit 12 Solutions- Page 12 of 14

Review Sheet – Solutions & Colligative Properties

Molarity – Perform the following molarity calculations:

1.) What is the molarity of 35 g of salt in 1.6 L of solution.

2.) What is the molarity of 12.8 g of calcium acetate in 876mL of solution?

3.) How many grams of salt are required to make 674mL of a 2.5 M solution?

4.) How much concentrated 12 M nitric acid solution is required to prepare 100 ml of a 2.0 M

solution?

Net Ionic Equations Write net ionic equations for the following:

5.) The reaction of acetic acid (HC2H3O2) with potassium hydroxide

6.) The reaction of calcium chloride with sodium sulfate

7.) The reaction of copper (II) nitrate with sodium chloride.

Solubility curve – use the graph on page 11 of this packet to answer these!

8) At 20 0C how much KNO3 is soluble in 200 g of water?

9) Which salt is least soluble at 30 0C?

10) At what temperature will 60 g of ammonium chloride form a saturated solution with 100

g of water?

Unit 12 Solutions- Page 13 of 14

Lab Chromatography

Read pgs 828 (intro)

Pre-lab question:

1. Define chromatography.

Procedure:

Equipment: goggles 1 large test tube test tube rack

filter paper strips Washable black pen (use Ms. Clark’s pens!)

Procedure:

1. Use a pencil to mark a small circle, the size of the printed letter o, about 2 cm from one

end of a piece of filter paper strip. (strip should be long enough to go from the bottom to

the top of your test tube and the sides of the strip should not be bent when placed in the

test tube).

2. Place a dot of black ink into the o. – allow the ink to dry.

3. Fill a test tube with water to a little less than 2 cm.

4. Place the filter paper strip into the test tube. The end of strip should be below the water

level; the dye spot must be above the water level (do not allow it to get wet!)

5. Set the tube to the side where it will be allowed to sit for the rest of the station time

6. At the end of the period go back to your tube and pull out your filter paper. Throw it

away after observing the changes!

Questions:

1 What happened to your filter paper. Explain

2 Did the ink undergo a physical or chemical change?

3 Classify the black ink as an element, compound, solution or heterogeneous mixture.

___________

4 What factors helped you make the above classification?

Unit 12 Solutions- Page 14 of 14

Molarity lab – layered solution

Materials: food coloring,salt, cups, stirring rod, pipettes, graduated cylinder (10 ml), water,

balance

Procedure: 1. Calculate the mass of salt needed to make each of the solutions below. Copy

the chart onto your lab write up . Have your teacher check your calculations before you

continue!

Cup Molarity mL of water Grams NaCl Food coloring

1 4.0 25.0 Blue

2 2.5 25.0 Green

3 1.0 25.0 Yellow

4 0 25.0 Red

2. Into each of the 4 labeled cups place salt and water in the amounts identified in the

chart above. Add 2 drops of food coloring to each cup.

3. Using the stirring rod stir until all salt dissolves.

4. Very carefully transfer 2 mL from cup 1 to the graduated cylinder.

5. Using a large pipette, layer 2 mL from the 2.5M solution on top of the first layer in the

graduated cylinder. . The goal is NOT to mix the solutions. Do not tilt the cylinder during

the process; this will favor mixing of layers.

6. Then carefully layer 2 ml of cup 3 on top. Continue with 4.

Observations: Make a colored drawing of your layered solution on your paper.

Questions: Answer these questions– you do not have to copy the questions or write a

conclusion.

1. Which is the most dense solution?__________________________ DRAWING BELOW!

2. The least dense?____________________________

3. How is density related to molarity?___________________________

4. Why don’t the layers mix?_____________________________

5. Which of the solutions you mixed was most concentrated?

___________________________

6. Would the salt or the water be considered the solute?

_________________________

7. Would the salt or the water be considered the solvent?

_____________________________

8. Which of the solutions contained more solute?

________________________