ch 13 solutions!

CH 13 Solutions!

Solution = stable homogeneous mixture; has the same composition throughout, does not settle out, and particles are dissolved; can’t distinguish phases under a microscope

• The solute is what gets dissolved and the solvent is what does the dissolving.

• In salt water the salt is the solute and water is the solvent.

Not all solutions are liquids only:1. Solid in a liquid = salt water2. Gas in a liquid = soda pop (carbon dioxide in

water) or in a lake dissolved oxygen in water.3. Gas in Gas = Air around us is mixture of

mainly nitrogen and oxygen4. Liquid in liquid = alcohol in water5. Solid in a solid = these are also known as

alloys.

5 ounces of wine24 proof

24 ÷ 2 = 12 (% alcohol)

12 ÷ 100 = 0.12 0.12 x 5 oz

=0.6 ounces ethanol

12 ounces of beer10 proof 10 ÷ 2 = 5

(% alcohol) 5 ÷ 100 = 0.05

0.05 x 12 oz=

0.6 ounces ethanol

1 1/2 shot80 proof

80 ÷ 2 = 40 (% alcohol)

40 ÷ 100 = 0.4 0.4 x 1.5 oz

=0.6 ounces ethanol

Ex. Liquid in liquid mixture

FYI

Other types of alcohol are not safe to drink. They can be toxic and even fatal is consumed. They include:

•Butyl alcohol, or butanol. This type of alcohol, derived from butane, is commonly used in products such as adhesives and varnishes.

FYI

• Methyl alcohol, also known as methanol or wood alcohol. It is used in the manufacture of formaldehyde and as industrial solvent. During Prohibition wood alcohol gained notoriety as a mixing agent with ethyl alcohol to make liquor.

• Several people became blind after drinking this toxic mixture, as methyl alcohol causes swelling of the optic nerve, an irreversible condition.

FYI

• Isopropyl alcohol, also known as rubbing alcohol, is a common household product. It is used as a disinfectant and as an ingredient in cologne and after-shave lotion.

• Ethylene glycol, also known as antifreeze, is the most harmful type of alcohol. It should never be consumed, as it is deadly.

Examples of Alloys:

Brass – copper + zincBronze – copper +

tin/aluminumSteel – iron, carbon + othersWhite gold – gold + Ni + PdWrought iron – iron + carbon

13.2 Concentration & Molarity

• In a solution, the solute is distributed evenly throughout the solvent.

• Any part of the solution has the same solute to solvent ratio or concentration

• Concentrations can be expressed in many forms Ex. molarity, ppm, molality

Name Abbreviation or symbol

Units Areas of Application

Molarity M mol soluteL solution

Solution stoichiometry

Molality m mol solutekg solvent

calc. of colligative properties

Parts per million

ppm g solute1000 000 g solution

To express small concentrations

Parts per million (ppm) = gram solute per one million grams solvent; used in measurements such as pollution that involve very low concentrations

1 mg/L = 1 ppmEx. Lead in drinking water

ppm = gram solute 1 000 000 g solution

• “Parts” are measured by mass

Sample Problem A p. 461A chemical analysis shows that there are 2.2 mg of lead in exactly 500 g of a water sample (solution). Convert to ppm. (grams solute/one million grams solution)

Convert mg to grams

2.2 mg x =

Divide by 500 grams to get the grams (parts) in 1 gram of water. Multiply by 1 000 000 to get the amount of grams in 1 000 000 g water.2.2 x 10-3 g of Pb x 1 000 000 parts = 4.4 ppm Pb in the water 500 g H2O 1 million

• 4.4 grams of lead for every 1 000 000 grams of solution• 0.000 004 4 grams of lead for every 1 gram of solution

1 gram1000 mg

2.2 x 10-3 g of Pb

Practice Problems #1-7 p. 461

1. Helium gas, 3.0 x 10-4g, is dissolved in 200.0g of water. Express in ppm.

3.0 x 10-4g He200.0 g H20

x 1 000 000 parts 1 million

= 1.5 ppm

Practice Problems #1-7 p. 4612. A sample of 300.0g of drinking water is found

to contain 38 mg Pb. Express in ppm.

0.038 g Pb300.0 g H20

x 1 000 000 parts 1 million

= 126.6 = 130 ppm

38 mg Pb x 1 g = 0.038 g 1000 mg

Practice Problems #1-7 p. 461

3. A solution of lead sulfate contains 0.425 grams of lead sulfate in 100.0 grams of water. Express in ppm.

0.425 gPbSO4

100.0 g H20

x 1 000 000 parts 1 million

= 4250 ppm

Practice Problems #1-7 p. 461

4. A 900.0 g sample of sea water is found to contain 6.7 x 10-3 g Zn. Express in ppm.

6.7 x 10-3 g Zn. 900.0 g H20

x 1 000 000 parts 1 million

= 7.4 ppm

Practice Problems #1-7 p. 4615. A 365.0 gram sample of water contains 23

mg Au. Express in ppm.

0.023 g Au365.0 g H20

x 1 000 000 parts 1 million

= 63 ppm

23 mg Au x 1 g = 0.023 g 1000 mg

Practice Problems #1-7 p. 4616. A 650.0 g hard-water sample contains 101

mg Ca. Express in ppm.

0.101 g Ca650.0 g H20

x 1 000 000 parts 1 million

= 155 ppm

101 mg Ca x 1 g = 0.101 g 1000 mg

Practice Problems #1-7 p. 4617. An 870.0 g river water sample contains 2.0

mg Cd. Express in ppm.

0.0020 g Cd870.0 g H20

x 1 000 000 parts 1 million

= 2.3 ppm

2.0 mg Cd x 1 g = 0.0020 g 1000 mg

Which of the following would be the most concentrated solution? (Hint: density of water 1g/1mL)

A. 200 g of C12H22O11 in 1 kg of water

B. 1000 ppm of C12H22O11 in water

C. 1500 ppm of C12H22O11 in water

D.1 mol of C12H22O11 in 1 L of solutionA. 200 grams C12H22O11 x 1000 0000 = 200 000 ppm 1000 grams water 1 million

D. 1 mol = 12(12) + 22(1) + 11(16) = 342 g SO 1 L x 1000 mL x 1 g = 1000 g 1 L 1 mL 342 grams C12H22O11 x 1000 0000 = 342 000 ppm 1000 grams water 1 million

Application:p. 489 # 37-40

Molarity

• Allows chemists to describe the number of solute particles in a volume of total solution (not just solvent)

Molarity = moles of solute dissolved in a liter of solution

M = mol/L (read “moles per liter” or “molar”)

[ ] = molarity (in aqueous solution)

[CuSO4] = 0.5 M

The molarity of copper sulfate is 0.5 M or moles per liter.

[NaNO3] = 1.0 M

The molarity of sodium nitrate is 1.0M. Also called a 1 molar solution.

Sample B p.465Calculating Molarity

Molarity = moles of solute liters of solution

What is the molarity of a potassium chloride solution that has a volume of 400.0 mL and contains 85.0g KCl?

Step 1 Convert solute to moles.85.0 g KCl x 1 mol = 1.14 mol KCl 74.55 g KCl

Step 2 Convert solution to liters.400.0 mL x 1L = 0.400 L 1000 mLStep 3Divide moles by liters. 1.14 mol KCl = 2.85 M KCl

0.400 L

Practice p. 465 #1-7 Calculate molarity of the given solutions.1. Vinegar contains 5.0g of acetic acid, CH3COOH,

in 100.0 mL of solution. 5.0 g x 1 mol = 0.083 mol acetic acid 60 g

0.083 mol = 0.83 M acetic acid solution0.100 L

2. If 18.25g HCl is dissolved in enough water to make 500.0mL of solution, what is the molarity of the solution?

18.25 g x 1 mol = 0.5005 mol HCl 36.46g

0.5005 mol = 1.001 M hydrochloric acid solution0.500 L

3. If 20.0 g H2SO4 is dissolved in enough water to make 250.0mL of solution, what is the molarity of the solution?

20.0 g x 1 mol = 0.204 mol 98.09g

0.204 mol = 0.816 M sulfuric acid solution0.2500 L

4. A solution of AgNO3 contains 29.66 g of solute in 100.0 mL of solution. What is the molarity of the solution?

29.66 g x 1 mol = 0.175 mol 169.9g

0.175 mol = 1.75 M silver nitrate solution0.1000 L

5. A solution of barium hydroxide, Ba(OH)2, contains 4.285 g of solute in 100.0 mL of solution. What is the molarity of the solution?

4.285 g x 1 mol = 0.0250 mol 171.35g

0.0250 mol = 0.2501 M barium hydroxide solution

0.1000 L

6. What mass of KBr is present in 25 mL of a 0.85 M solution of potassium bromide?

x mol = 0.85M x = 0.85 mol X 0.025 L = 0.021 mol0.025L L

0.021 mol KBr x 119 g = 2.5 g KBr 1 mol

7. If all of the water in 430.0 mL of 0.45 M NaCl solution evaporates, what mass of NaCl will remain?

x mol = 0.45M x = 0.45 mol X 0.4300 L = 0.19 mol0.4300 L L

0.19 mol NaCl x 58.44 g = 11 g NaCl 1 mol

Application: p. 489 # 41-45

9.2 Review p. 467# 2,4-9

Preparing a Solution of Specified Molarity

If you add 1.000 mol solute to 1.000 L of solution, the molarity would NOT be 1.000M.

Why not???

•The added solute would change the total volume of the solution.•Molarity would be = 1 mol = 0.83M

1.2 L

Preparing 1.000L of solution (p. 463)1. Convert moles to mass using molar mass. 2. Measure amount needed in grams. 3. Add small amount water (solvent) to beaker and

dissolve.4. Pour into 1.000 L volumetric flask.5. Rinse beaker and pour into flask.6. Stopper flask & swirl.7. Carefully add water to 1.000L mark on flask.8. Stopper & invert at least 10 times.

• Why don’t you fill with water to the 1000 mL mark and then add solute?Because then the total volume of the solution will be greater than 1000 mL.

• Video

Application: Molarity Lab

Dilution = adding more solvent to a solution so that the concentration of the solute becomes lower.

•The total number of solute particles in the solution remains the same after dilution, but the volume of the solution becomes greater, resulting in a lower molarity, ppm, mg/L, or % concentration.

• Dilution video• Dilution – Preparation of Solutions

• END OF PART 1 NOTES

13.3 Solubility & Dissolving

Solubility = ability of one substance to dissolve into another at a given temperature & pressure.

Dissolving Liquids

Miscible = 2 liquids that are able to dissolve into each other

Immiscible = do not mix; form 2 layers upon settling, droplets when mixed

These liquids are immiscible. Nonpolar molecules form droplets

• Two mutually immiscible liquids in a cylinder are heated with a light bulb.

• The density of the liquids change as they are heated and cooled.

DISSOLVING SOLIDSSolvation (aka dissolution) =

process of breaking apart the crystal lattice of ionic solids

Hydration = as ions dissolve in a solvent they spread out and become surrounded by solvent molecules.– Water molecular are polar– Partially positive hydrogen surrounds neg. ions– Partially negative oxygen surrounds pos. ions

Ex. Video Dissolution of KMnO4

Solubility depends on

1.Nature of solute & solvent molecules

2.Surface area

3.Temperature

4.Pressure (for gases only)

1. Nature of Solute/Solvent - POLARITY“Like dissolves like”• A polar covalent solvent will dissolve ionic

solutes and other polar covalent solutes• A nonpolar covalent solvent will dissolve

nonpolar solutesVideo

• Why no discussion of ionic solvents?

• Water is a common example of a polar solvent.

• Carbon tetrachloride is a common example of a nonpolar solvent – unequal sharing geometrically cancels/balances

immiscible

Iodine Crystals

• The purple iodine crystal remains undissolved (insoluble) in the water

• Iodine has dissolved (soluble) in the CCl4

• Iodine molecules are nonpolar (identical atoms share equally).

nonpolar

Sugar

• You can see that the sugar has dissolved in the water but has not dissolved in the carbon tetrachloride

• Sugar molecules contain polar angular C-O-H groups.

WATER CCl4

WATER CCl4

Ethanol

• Miscible with both. • Half of each ethanol

molecule contains a polar C-O-H group and the other half contains essentially nonpolar C-H bonds.

• That gives ethanol molecules both polar and nonpolar characteristics.

WATER CCl4

• There are many degrees of polarity, all sorts of gradations in between the extremes of polar and nonpolar.

Ex. The solubility of nonpolar iodine increases as the polarity of the solvent decreases.

WATER CCl4ACETONE ETHANOL

2. Surface Area• Greater the surface exposed to the

solvent, the faster dissolving occurs– Coarse salt vs. table salt – smaller

pieces– Mixing/shaking – increases contact

• What does a sugar cube have to do with this concept?

• Same mass of granules dissolve faster than cube

3. Temperature

• For most solids, solubility increases as temperature increases

• As temperature increases, solvent particles move faster and collide more often with surface of solute

From left to right temperature increases, does the curve of solubility increase, stay the same, or decrease?

1. NaNO3 & many others

2. NaCl3. Ce2(SO4)3

• For most gases, solubility decreases as temperature increases

• A short metal rod is heated and then dropped into a freshly opened bottle of root beer.

• A fountain of foam shoots out since carbon dioxide is less soluble in warm root beer than cold root beer.

Saturation= a solution that cannot dissolve any more

solute under the given conditions• As long as a solution is unsaturated, more

solute can be added and dissolved• What evidence can you see that might

indicate that this solution is saturated?

Supersaturated Solutions

= solution holding more than normal dissolved solute at a given temperature.

• Heat to dissolve, then allow to cool• Cooled – add seed crystal and excess solute

comes out of solution.Video: Sodium AcetateExample: hot packs (same chemical)

• Homework: Worksheet 13.3

19.4 Physical Properties of Solutions1. Conduct electricity if contain charged

particles (ions)– Nonelectrolytes do not increase the electrical

conductivity of water– Electrolytes do increase the electrical conductivity

of water• Weak electrolytes cause a mild increase• Strong electrolytes cause a greater increase

Electrical Conductivity of Solutions

Electrocuting a Pickle

Non-electrolytes

Strong electrolyte

Weak electrolyte

Dissolution of an Ionic and a Covalent Compound

• Does tap water conduct electricity?• Does pure water conduct electrity?

Water only conducts electricity if it contains dissolved electrolytes.

• Is bottled water pure water?• Is distilled water pure water?

2. Colligative Properties

• The next time you see a container of antifreeze, look on the label and it will show you that as you increase the amount (concentration, actually) of the antifreeze in the car's cooling system the freezing point of the solution decreases. There is a limit to that, and the instructions usually say that you should not exceed a certain percentage. If you get to the point where you have water in the antifreeze rather than antifreeze in the water, the freezing point starts going back up--although it is still very low.

• In general, for dilute solutions, the amount of change in the freezing point is proportional to the concentration of the solute in the solution.

• The effect on the boiling point is just the opposite; that is, the boiling point of a liquid is increased if something is dissolved in it.

• Again, the antifreeze in a car radiator is an example of this. In the advertisements it's called summer protection against boil-overs. Essentially what they have done is raised the boiling point of the liquid, of the water, by making it a solution.

• Emulisifier

Kerosene and water are shaken together and separate rapidly. Adding liquid soap to the mixture produces a temporary emulsion when the flask is shaken again. The emulsion separates slowly.