PACKET #9 Solutions Textbook: Chapter 15 Reference Table: F, G, & T .

PACKET #9PACKET #9SolutionsSolutions

Textbook: Chapter 15Textbook: Chapter 15Reference Table: F, G, & TReference Table: F, G, & T

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Let’s Review a little . . .Let’s Review a little . . . A solution is a A solution is a homogenous mixturehomogenous mixture

homogeneous mixture of substances in the same homogeneous mixture of substances in the same physical statephysical state

contains atoms, ions, or molecules of one contains atoms, ions, or molecules of one substance spread uniformly throughout a second substance spread uniformly throughout a second substancesubstanceWhen salt (NaCl) is stirred into water, the When salt (NaCl) is stirred into water, the individual Na+ and Cl- ions separate and individual Na+ and Cl- ions separate and uniformly spread throughout the water, forming uniformly spread throughout the water, forming a solutiona solution

appears to be one substance appears to be one substance

Solid Solutions:Solid Solutions:

A solid may be A solid may be dissolved in dissolved in another solidanother solid

Brass is a solution Brass is a solution of zinc and copperof zinc and copper

When metals are When metals are mixed together to mixed together to form a solution, the form a solution, the result is called anresult is called an ALLOYALLOY

Gaseous Solutions:Gaseous Solutions:

Air is an example Air is an example of a mixture of of a mixture of gases that form a gases that form a solutionsolution

Although solutions Although solutions exist in all three exist in all three states the most states the most common type of common type of solution is one in solution is one in which a solid or a which a solid or a liquid is dissolved liquid is dissolved in another liquidin another liquid

Solution:Solution: a homogenous mixture made up a homogenous mixture made up of two or more substances. A solution is of two or more substances. A solution is made up of a made up of a solutesolute and a and a solvent.solvent.

Solute:Solute: a substance like salt or sugar that a substance like salt or sugar that dissolves in a solvent like water.dissolves in a solvent like water.

Solvent:Solvent: usually a liquid, for example water. usually a liquid, for example water. If the solvent is water, then the solution is If the solvent is water, then the solution is called an called an aqueous solution (aq).aqueous solution (aq).

Precipitate:Precipitate: a substance that is a substance that is caused to become caused to become insolubleinsoluble by heat by heat or chemical reagent and separate out or chemical reagent and separate out from a solution. Example: salt and from a solution. Example: salt and water, boil, evaporate water, and the water, boil, evaporate water, and the salt that remains are known as the salt that remains are known as the precipitate.precipitate.

Solubility: Solubility: the most substance that the most substance that can dissolve in the water (a solvent) at can dissolve in the water (a solvent) at a specific temperature. Different a specific temperature. Different substances react differently (TABLE G).substances react differently (TABLE G).

DissolvingDissolving The solvent molecules have enough The solvent molecules have enough

attraction for the solute particles to attraction for the solute particles to break the intermolecular forces between break the intermolecular forces between solute particles. solute particles.

Solvent particles are attracted to the Solvent particles are attracted to the solute particles and bring the solute into solute particles and bring the solute into the solution. the solution.

Factors Affecting the Rate Factors Affecting the Rate of Dissolvingof Dissolving

Three important factors that affect rate of Three important factors that affect rate of dissolving are dissolving are surface area, stirring, and surface area, stirring, and temperature.temperature.

SURFACE AREA:SURFACE AREA: The greater the SA, the faster the substance will The greater the SA, the faster the substance will

dissolve.dissolve.

More solute particles can come in contact with the More solute particles can come in contact with the solvent and be pulled into solution.solvent and be pulled into solution.

This is why granulated sugar will dissolve faster This is why granulated sugar will dissolve faster than a cube of sugar.than a cube of sugar.

STIRRING:STIRRING: Increased stirring causes a substance to dissolve Increased stirring causes a substance to dissolve

faster.faster.

More solute particles can come in contact with More solute particles can come in contact with the solvent and be pulled into solution.the solvent and be pulled into solution.

This is why people stir lemonade or iced tea This is why people stir lemonade or iced tea mixes.mixes.

TEMPERATURE:TEMPERATURE: For solids and liquids, increasing temperature For solids and liquids, increasing temperature

increases the rate of dissolving. increases the rate of dissolving.

This allows more solvent particles to collide with This allows more solvent particles to collide with the solute.the solute.

For gases, increasing the temperature For gases, increasing the temperature decreasesdecreases the rate of dissolving. the rate of dissolving.

The gas is more able to evaporate out The gas is more able to evaporate out of the solution.of the solution.

This is why soda should be refrigerated This is why soda should be refrigerated and why it becomes flat if left open.and why it becomes flat if left open.

Remember . . .Remember . . . ““Likes dissolve in likes”Likes dissolve in likes” Polar solutes will Polar solutes will onlyonly dissolve in dissolve in

polar solvents.polar solvents. Non-polar solutes willNon-polar solutes will only only dissolve in dissolve in

non-polar solvents.non-polar solvents. Polar in PolarPolar in Polar Non-polar in Non-polar in

PolarPolar

Table G: Solubility CurveTable G: Solubility Curve

HCl

NH3

SO2

TABLE G:TABLE G: Solubility Curve, the horizontal line Solubility Curve, the horizontal line in the graph shows temperature, and the in the graph shows temperature, and the vertical line shows how many grams of a vertical line shows how many grams of a solute is the most that can dissolve in 100 solute is the most that can dissolve in 100 grams of water.grams of water.

The various compounds on the graph The various compounds on the graph (solutes) dissolve differently at different (solutes) dissolve differently at different temperature, and for a given temperature temperature, and for a given temperature only a certain amount of the solutes can only a certain amount of the solutes can dissolve in 100 grams of water.dissolve in 100 grams of water.

Some of the solutes on the graph are in solid Some of the solutes on the graph are in solid form, and some are in gas form.form, and some are in gas form.

This graph represents that This graph represents that temperature temperature does have an effect on solubility.does have an effect on solubility.

Solubility of a Solubility of a solidsolid (KNO (KNO33, NaNO, NaNO33) ) increases as temperature increases.increases as temperature increases.

Solubility of a Solubility of a gasgas (NH (NH33, HCl) , HCl) decreases as temperature increases.decreases as temperature increases.

HCl

NH3

SO2

Table G: Solubility CurveTable G: Solubility Curve Concentrated: Concentrated: a large amount of solute a large amount of solute

per grams of solvent; there is a large per grams of solvent; there is a large concentration of solute.concentration of solute.

Dilute:Dilute: a small amount of solute per a small amount of solute per grams of solvent.grams of solvent.

There are three types of solutions:There are three types of solutions: saturatedsaturated unsaturatedunsaturated supersaturatedsupersaturated

Saturated SolutionSaturated Solution Contains the most solute that can dissolve at Contains the most solute that can dissolve at

a given temperature. If you added anymore a given temperature. If you added anymore of the solute it would not dissolve. of the solute it would not dissolve.

When you graph the solubility of a solvent, When you graph the solubility of a solvent, the line on the graph represents saturated; the line on the graph represents saturated; all the lines on Table G are saturated!!!all the lines on Table G are saturated!!!

Example: Look at KNOExample: Look at KNO33 at 70°C, the at 70°C, the maximum amount of the salt that can maximum amount of the salt that can dissolve in 100 grams of water is about 134 dissolve in 100 grams of water is about 134 grams, so the line for saturated can only grams, so the line for saturated can only hold 134 grams of KNOhold 134 grams of KNO33..

Unsaturated SolutionUnsaturated Solution

Contains less solute than a saturated Contains less solute than a saturated solution. You can still add more salt solution. You can still add more salt and it will dissolve. and it will dissolve.

Example: At 70°C, if you have 130 Example: At 70°C, if you have 130 grams of KNOgrams of KNO33, this would be an , this would be an unsaturated solution because you can unsaturated solution because you can still add 4 grams of KNOstill add 4 grams of KNO33 before the before the solution is saturated.solution is saturated.

Supersaturated SolutionSupersaturated Solution This is only a temporary situation caused by This is only a temporary situation caused by

slowly cooling a saturated solution. It has slowly cooling a saturated solution. It has more solute than in a saturated solution. more solute than in a saturated solution.

A supersaturated solution is very unstable A supersaturated solution is very unstable and the amount in excess can precipitate or and the amount in excess can precipitate or crystallize.crystallize.

Example: At 70°C, if you have 137 grams Example: At 70°C, if you have 137 grams of KNOof KNO33, this would be an supersaturated , this would be an supersaturated solution because you have more than 134 solution because you have more than 134 grams of solute per 100 grams of water.grams of solute per 100 grams of water.

Pressure Affects Pressure Affects SolubilitySolubility

We have already learned that temperature has We have already learned that temperature has an affect on solubility, and that the nature of the an affect on solubility, and that the nature of the solute/solvent has an affect on solubility (polar solute/solvent has an affect on solubility (polar vs. non-polar)vs. non-polar)

Pressure also has an effect on solubility.Pressure also has an effect on solubility.

Pressure makes gases more soluble, and has Pressure makes gases more soluble, and has almost no effect of liquids or solids.almost no effect of liquids or solids.

Example: High pressure forces carbon dioxide Example: High pressure forces carbon dioxide gas into water to make soda; makes carbon gas into water to make soda; makes carbon dioxide more soluble. When you open the cap of dioxide more soluble. When you open the cap of soda, there is less pressure, the soda fizzes, and soda, there is less pressure, the soda fizzes, and gas escapes.gas escapes.

Soluble or Insoluble? (Table Soluble or Insoluble? (Table F)F)S

olu

ble

Inso

luble

Inso

luble

Solu

ble

NH4+

Ions that are soluble (have the Ions that are soluble (have the highest highest concentration of dissolved ions)concentration of dissolved ions) can can conduct electricity (are electrolytes)conduct electricity (are electrolytes)

Ions that are insoluble (have the Ions that are insoluble (have the lowest lowest concentration of dissolved ions) concentration of dissolved ions) cannot conduct electricity (are non-cannot conduct electricity (are non-electrolytes or poor electrolytes)electrolytes or poor electrolytes)

Electrical conductivity decreases when the Electrical conductivity decreases when the concentration of ions decreases.concentration of ions decreases.

Remember that a precipitate is Remember that a precipitate is always always considered insoluble.considered insoluble.

Question: Are the following soluble? Question: Are the following soluble? NaCl, AgBr, NaCl, AgBr, CaCOCaCO33, (NH, (NH44))22SS

Question: Based on Table F, which of the Question: Based on Table F, which of the following saturated solutions has the lowest following saturated solutions has the lowest concentration of dissolved ions? (meaning concentration of dissolved ions? (meaning insoluble) NaCl, MgClinsoluble) NaCl, MgCl22, NiCl, NiCl22 or AgCl? or AgCl?

Be Be Specific . . .Specific . . .

Sometimes it is adequate to refer to a solution as Sometimes it is adequate to refer to a solution as dilute or concentrated, but dilute and dilute or concentrated, but dilute and concentrated are concentrated are relative termsrelative terms and are not and are not precise with regards to the amount of solute precise with regards to the amount of solute involvedinvolved

In most cases it is very important to know the In most cases it is very important to know the specific amount of solute specific amount of solute (the (the concentration)concentration) of a solution of a solution

There are several methods of expressing the There are several methods of expressing the specific concentration of a solute in a solutionspecific concentration of a solute in a solution

You can describe the concentration of a solution You can describe the concentration of a solution by by molarity, molality, percent by mass, or molarity, molality, percent by mass, or parts per million.parts per million.

Molarity (Table T)Molarity (Table T) The molarity of a solution is the number The molarity of a solution is the number

of moles of solute in one liter of a of moles of solute in one liter of a solution. solution.

Molarity (M) = moles of soluteMolarity (M) = moles of solute liters of liters of

solutionsolutionWARNING!!! Triple Threat:WARNING!!! Triple Threat:1. May not give you moles (given/GFM)2. May not give you liters (convert mL L)3. Liters of solution (solute + solvent; may have

to add them together)

Molarity (Table T)Molarity (Table T)Question:Question: How many grams of NaCl would you How many grams of NaCl would you

need for a .5M solution?need for a .5M solution?

Question:Question: How many moles of solute are How many moles of solute are contained in 200 mL of a 1M solution? contained in 200 mL of a 1M solution?

Question:Question: If you have 50 moles of a solute in If you have 50 moles of a solute in 25 liters of solution, what is the molarity?25 liters of solution, what is the molarity?

We said before that the higher the We said before that the higher the concentration of ions (more ions), the better concentration of ions (more ions), the better the solution conducts electricity. When the solution conducts electricity. When comparing a 1M solution of NaCl to a 5M of comparing a 1M solution of NaCl to a 5M of NaCl, the 5M of NaCl is a better conductor of NaCl, the 5M of NaCl is a better conductor of electricity than the 1M of NaCl.electricity than the 1M of NaCl.

Molality Molality There are certain situations in which we There are certain situations in which we

must know how much solvent is present in must know how much solvent is present in a solution. a solution.

Molality Molality is defined as the number of moles is defined as the number of moles of solute dissolved in 1 kilogram of solute.of solute dissolved in 1 kilogram of solute.

Molality (m) = moles of Molality (m) = moles of solutesolute

Kg of solventKg of solvent

WARNING!!! Double Threat:WARNING!!! Double Threat:1. May not give you moles (given/GFM)2. May not give you Kg (convert g Kg)

MolalityMolalityQuestion: Question: Sucrose (table sugar) as a Sucrose (table sugar) as a

molar mass (GFM) of 342 grams per molar mass (GFM) of 342 grams per mole. What is the molality of a mole. What is the molality of a solution prepared by dissolving 34.2 solution prepared by dissolving 34.2 grams of sucrose in 200 grams of grams of sucrose in 200 grams of water?water?

Question: Question: What is the molality of a What is the molality of a solution prepared by dissolving 51 solution prepared by dissolving 51 grams of NHgrams of NH33 in 2.0 kilograms of H in 2.0 kilograms of H22O?O?

Parts Per Million (ppm) Parts Per Million (ppm) (Table T)(Table T)

A unit of concentration that expresses the A unit of concentration that expresses the mass of a solute dissolved in 1 million parts mass of a solute dissolved in 1 million parts of a very diluted solution. of a very diluted solution.

ppm = grams of solute x ppm = grams of solute x 1,000,0001,000,000

grams of solutiongrams of solution

WARNING!!! Triple Threat:WARNING!!! Triple Threat:1. May not give you grams of solute

(given/GFM)2. May not give you grams of solution (mg

g)3. Grams of solution (solute + solvent; may

have to add them together)

Percent by MassPercent by Mass Similar concept as percent composition (part/whole Similar concept as percent composition (part/whole

x 100). Looking to calculate the percent mass of x 100). Looking to calculate the percent mass of solute in the whole solution.solute in the whole solution.

% Mass = grams solute x 100% Mass = grams solute x 100 grams solutiongrams solution

WARNING!!! Triple Threat:WARNING!!! Triple Threat:1. May not give you grams of solute (given/GFM)2. May not give you grams of solution (convert mg

g)3. Grams of solution (solute + solvent; may have to

add them together)

Parts Per Million & % Parts Per Million & % MassMass

Question: Question: A CuSOA CuSO44 solution contains .05g of solution contains .05g of CuSOCuSO44 in 1000g of solution. What is the in 1000g of solution. What is the concentration of the solution in parts per million?concentration of the solution in parts per million?

Question: Question: What are the grams of solute required to What are the grams of solute required to make a 3 ppm solution when the amount of water make a 3 ppm solution when the amount of water is 150g?is 150g?

Question: Question: In percent by mass, what is the In percent by mass, what is the concentration of 85.6g of hydrochloric acid in concentration of 85.6g of hydrochloric acid in 356g of solution?356g of solution?

Parts Per Million & % Parts Per Million & % MassMass

Question: Question: What are the parts per million if What are the parts per million if a solution contains 75g of solute in 150g a solution contains 75g of solute in 150g of solution?of solution?

Question: Question: 8 grams of NaCl is dissolved 8 grams of NaCl is dissolved in 100 grams of solution, what is the in 100 grams of solution, what is the percent by mass of NaCl?percent by mass of NaCl?

Molarity by DilutionMolarity by Dilution Dilution - Dilution - the process of adding more the process of adding more

solvent to a solution. solvent to a solution.

**Important****Important**

We’re not changing the number of moles, We’re not changing the number of moles, just the volume of solvent. The moles of just the volume of solvent. The moles of solute are equal in the concentrated and solute are equal in the concentrated and dilute solutionsdilute solutions..

Before Dilution After DilutionBefore Dilution After Dilution

Molarity by DilutionMolarity by Dilution

MM11VV11 = M = M22VV22

MM11 = initial concentration (molarity) = initial concentration (molarity)

VV11 = initial volume = initial volume

MM22 = final concentration (molarity) = final concentration (molarity)

VV22 = final volume = final volume

Molarity by DilutionMolarity by Dilution

Question: Question: A teacher wants to prepare 500. A teacher wants to prepare 500. mL of 1.00 M solution of acetic acid from mL of 1.00 M solution of acetic acid from 17.5 M stock solution. What volume of the 17.5 M stock solution. What volume of the stock solution is required?stock solution is required?

Question: Question: What volume of 16M sulfuric acid What volume of 16M sulfuric acid must be used to prepare 1.5L of a 0.10 M must be used to prepare 1.5L of a 0.10 M solution?solution?

Question: Question: What volume of 12 M HCl must What volume of 12 M HCl must be taken to prepare 0.75 L of 0.25M HCl?be taken to prepare 0.75 L of 0.25M HCl?

Colligative PropertiesColligative Properties

Boiling Point Elevation:Boiling Point Elevation: Rule: The presence of a solute (salt or sugar) raises Rule: The presence of a solute (salt or sugar) raises

the boiling point of the solvent.the boiling point of the solvent. The greater the concentration of the solute, the The greater the concentration of the solute, the

more it raises the boiling point.more it raises the boiling point. Water boils at 100°C, by adding glucose to water; it Water boils at 100°C, by adding glucose to water; it

will raise the boiling point of water slightly. The will raise the boiling point of water slightly. The greater the concentration of solute, the higher the greater the concentration of solute, the higher the boiling point becomes.boiling point becomes.

Freezing Point Depression:Freezing Point Depression: Rule: The presence of any solute (salt or sugar) Rule: The presence of any solute (salt or sugar)

lowers the freezing point of the solvent.lowers the freezing point of the solvent. The freezing point of water is 0°C, by adding The freezing point of water is 0°C, by adding

glucose to water it lowers the freezing point slightly. glucose to water it lowers the freezing point slightly. The greater the concentration of the solute, the The greater the concentration of the solute, the lower the freezing point becomes.lower the freezing point becomes.

HOT GET HOTTER; COLD GET COLDERHOT GET HOTTER; COLD GET COLDER

Calculating the Freezing Calculating the Freezing and Boiling Points of and Boiling Points of

SolutionsSolutions∆∆TTbb = (i)(+k = (i)(+kbb )( )(m)m)

∆∆TTff = (i)(-k = (i)(-kff )(m) )(m)

∆∆TTb b & ∆T& ∆Tff = changes in BP & FP = changes in BP & FP i – ions (in ionic i – ions (in ionic dissociation; covalent dissociation; covalent

1)1) +k+kbb & -k & -kff = constants representing the number = constants representing the number

of degrees that the BP and FP of a solvent is of degrees that the BP and FP of a solvent is raised when 1 mole of a molecular, non-volatile raised when 1 mole of a molecular, non-volatile (does not evaporate with the solvent) solute is (does not evaporate with the solvent) solute is dissolved in 1 kilogram of the solventdissolved in 1 kilogram of the solvent

m = m = molalitymolality

kkbb = +0.513 °C/m = +0.513 °C/m kkff = -1.86 °C/m = -1.86 °C/m

Question: Question: What is the boiling point of What is the boiling point of a 2.0m solution of ethylene glycol in a 2.0m solution of ethylene glycol in water at 1 atm?water at 1 atm?

Question: Question: What is the boiling point of What is the boiling point of a 2.0m aqueous solution of NaCl?a 2.0m aqueous solution of NaCl?

Question: Question: What is the freezing point of What is the freezing point of a 2.0m solution of ethylene glycol in a 2.0m solution of ethylene glycol in water?water?

Review Questions1) What is the molarity of a solution of NaOH

if 2 liters of the solution contains 4 moles of NaOH? A) 2 M B) 8 M C) 80 M D) 0.5 M

2) How many moles of solute are contained in 200 milliliters of a 1 M solution? A) 1 B) 0.2 C) 200 D) 0.8

3) What is the total number of grams of NaI(s) needed to make 1.0 liter of a 0.010 M solution? A) 15 B) 0.15 C) 0.015 D) 1.5

4) At standard pressure when NaCl is added to water, the solution will have a A) lower freezing point and a lower boiling point than waterB) higher freezing point and a higher boiling point than waterC) higher freezing point and a lower boiling point than waterD) lower freezing point and a higher boiling point than water

5) According to the Solubility Guidelines chemistry reference table, which of these compounds is the least soluble in water? A) K2CO3 B) Ca3(PO4)2 C) KC2H3O2 D) Ca(NO3)2

6) How many liters of a 0.5 M sodium hydroxide solution would contain 2 moles of solute?A) 1 L B) 2 L C) 3 L D) 4 L

7) How many grams of KOH are needed to prepare 250 milliliters of a 2.00 M solution of KOH (formula mass = 56.0)? A) 112 g B) 28.0 g C) 2.00 g D) 1.00 g

8) A solution of KCl(aq) contains 15 grams of solute in 85 grams of water. What is the concentration of the solution in percent by mass? A) 0.20% B) 2.0% C) 15% D) 6.0%

9) Based on the Solubility Curves chemistry reference table, which substance is most soluble at 60°C?

A) NH3 B) KCl C) NH4Cl D) NaCl

10) A solution contains 90 grams of a salt dissolved in 100 grams of water at 10°C. The solution could be an unsaturated solution of

A) KI B) KCl C) NaCl D) KNO3

Questions 11 and 12 refer to the following:The graph below represents the solubility curves for

solute A and solute B.

11) Compare the solubility of solute A and solute B at 20DC and at 80DC.

12) At what temperature are solute A and solute B equally soluble in 100. grams of water?