2. Solutions (Lots of vocabulary)
Unit 7

3. Solvents + Solutes = Solutions
An aqueous solution is water that contains dissolved substances.
In a solution, the dissolving medium is the solvent.
In a solution, the dissolved particles are the solute.
A solvent dissolves the solute. The solute becomes dispersed in the solvent.
Solvents and solutes may be gases, liquids, or solids.
Solute particles can be atoms, ions, or molecules.
As individual solute ions break away from the crystal, the negatively and positively charged ions become surrounded by solvent molecules, and the ionic crystal dissolves.

4. The Key to Solvation
The process by which the positive and negative ions of an ionic solid become surrounded by solvent molecules is called solvation.
An electrolyte is a compound that conducts an electric current when it is in an aqueous solution or in the molten state.
All ionic compounds are electrolytes because they dissociate into ions.
Sodium chloride is a strong electrolyte and is a good conductor of electricity because nearly all the dissolved sodium chloride exists as separate, solvated Na+ and Cl– ions.

5. Nonelectrolytes
A weak electrolyte conducts electricity poorly because only a fraction of the solute in the solution exists as solvated ions.
A compound that does not conduct an electric current in either aqueous solution or the molten state is called a nonelectrolyte.

6. Standards and Targets Standards Clear Targets & essential questions
Utilize appropriate mathematical equations and processes to solve chemistry problems.
Identify and solve different types of stoichiometry problems (e.g., volume at STP to mass, moles to mass, molarity).
Convert among the quantities of a substance: mass, number of moles, number of particles, molar volume at STP.
Know and understand the vocabulary:
Aqueous
Solute
Solvent
Dissociation
solvation
Electrolyte
Strong
Weak
Non
Know and be able to use Henry’s Law in solving problems

7. Under Pressure S1/P1 = S2/P2
Changes in pressure have little effect on the solubility of solids and liquids, but pressure strongly influences the solubility of gases.
Gas solubility increases as the partial pressure of the gas above the solution increases.
(Why?)
Henry’s law states that at a given temperature, the solubility (S) of a gas in a liquid is directly proportional to the pressure (P) of the gas above the liquid.
S1/P1 = S2/P2
Practice. Show work below.
Check for Understanding
What two factors affect the solubility of a gas?
Temperature and pressure
What is the formula for Henry’s Law?
S1/P1 = S2/P2

10. Standards and Targets Standards Clear Targets & essential questions
Utilize appropriate mathematical equations and processes to solve chemistry problems.
Identify and solve different types of stoichiometry problems (e.g., volume at STP to mass, moles to mass, molarity).
Convert among the quantities of a substance: mass, number of moles, number of particles, molar volume at STP.
Know and understand the vocabulary:
Aqueous
Solute
Solvent
Dissociation
solvation
Electrolyte
Strong
Weak
Non
Know and be able to use Henry’s Law in solving problems

11. If 0. 55 g of a gas dissolves in 1
If 0.55 g of a gas dissolves in 1.0 L of water at 2 atm of pressure, how much will dissolve at 4.5 atm of pressure? (1.23 g/L) 
A gas has a solubility of 0.66 g/L at 10 atm of pressure. What is the pressure on a 1.0 L sample that contains 1.5 g of gas? (22.73 atm) 
If .68 g of a gas at 5 atm of pressure dissolves in 1.0 L of water at 25oC, how much will dissolve in 1.0 L of water at 8 atm of pressure and the same temperature? (1.09 g/L)
 A gas has a solubility of 1.46 g/L at 8 atm of pressure. What is the pressure of a 1.0 L sample that contains 2.7 g/L? (14.8 atm)
 If 1.2 g of a gas at 6 atm of pressure dissolves in 1.0 L of water at 25oC, how much will dissolve in 1.0 L of water at 3 atm of pressure and the same temperature? (.6 g/L)

12. Molarity
The concentration of a solution is a measure of the amount of solute that is dissolved in a given quantity of solvent.
A dilute solution is one that contains a small amount of solute.
A concentrated solution contains a large amount of solute.
Molarity (M) is the moles of solute dissolved in one liter of solution.
To calculate the molarity of a solution, divide the moles of solute by the volume of the solution.

13. Practice
moles/liters

14. moles
Molarity Liters
1.0 moles of potassium fluoride is dissolved to make 0.10 L of solution.
1.0 grams of potassium fluoride is dissolved to make 0.10 L of solution.
1.0 grams of potassium fluoride is dissolved to make 0.10 mL of solution.
952 grams of ammonium carbonate are dissolved to make 1750 mL of solution.
9.82 grams of lead (IV) nitrate are dissolved to make 465 mL of solution.
1 L = 1000 mL

15. Percent Solutions
Percent concentration by volume/volume ratio:
Percent concentration by mass/mass ratio:
The concentration of a solution in percent can be expressed in two ways:
as the ratio of the volume of the solute to the volume of the solution
or as the ratio of the mass of the solute to the mass of the solution.
Check for Understanding
Diluting a solution does NOT change what?
Amount of moles in solution/amount of solute
What are the two ways that concentration can be expressed?
Percent by volume and percent by mass

16. 1. What is the percent by mass of 5. 0 g of NaCl mixed with 80
1. What is the percent by mass of 5.0 g of NaCl mixed with 80. g of water? 2. What is the percent by mass of 25.0 g of sodium acetate mixed with 40. g of water? 3. What mass of NaOH is found in 40. g of a 10% by mass solution? How many moles of NaOH is this? 4. What mass of lithium chloride is found in 85 g of a 25% by mass solution? 5. A group of friends finish an entire 750mL bottle of Jack Daniels, labeled 90. proof. Using this information, find out how much alcohol was in this bottle. 6. How many g of NaCl are found in 60. g of a 4.0% (by mass) solution? 7. How many moles of NaOH are needed to make 120 g of a 15% solution? 8. What is the percent solution (by volume) when 50. mL of ethanol is diluted to 140 mL with water?

17. 1. What is the percent by mass of 5. 0 g of NaCl mixed with 80
1. What is the percent by mass of 5.0 g of NaCl mixed with 80. g of water? 2. What is the percent by mass of 25.0 g of sodium acetate mixed with 40. g of water? 3. What mass of NaOH is found in 40. g of a 10% by mass solution? How many moles of NaOH is this? 4. What mass of lithium chloride is found in 85 g of a 25% by mass solution? 5. A group of friends finish an entire 750mL bottle of Jack Daniels, labeled 90. proof. Using this information, find out how much alcohol was in this bottle. 6. How many g of NaCl are found in 60. g of a 4.0% (by mass) solution? 7. How many moles of NaOH are needed to make 120 g of a 15% solution? 8. What is the percent solution (by volume) when 50. mL of ethanol is diluted to 140 mL with water?
Ans: 1) 5.9% 2) 38% 3) 4.0 g, 0.10 mol 4) 21 g 5) 340mL 6) 2.4 g 7) 0.45 mol 8) 36%

18. Standards and Targets Standards Clear Targets & essential questions
Utilize appropriate mathematical equations and processes to solve chemistry problems.
Identify and solve different types of stoichiometry problems (e.g., volume at STP to mass, moles to mass, molarity).
Convert among the quantities of a substance: mass, number of moles, number of particles, molar volume at STP.
Determine the molarity (M) of a solution.
Determine the molality (m) of a solution.
Analyze a graph to determine the effects of concentration on solutions.
Construct an appropriate graphical relationship for a data set.
How is solubility of a solution expressed?
What factors affect solubility?
How do you calculate the molarity of a solution?
What are the three colligative properties of a solution?
How does molality relate to colligative properties?
In what ways are molarity and molality different? Similar?

19. Solutions and Molality
Colligative Properties
A property that depends only upon the number of solute particles, and not upon their identity, is called a colligative property.
Three important colligative properties of solutions are
vapor-pressure lowering
boiling-point elevation
freezing-point depression

20. Solutions and Molality
Molality and Mole Fraction
The unit molality and mole fractions are two additional ways in which chemists express the concentration of a solution.
The unit molality (m) is the number of moles of solute dissolved in 1 kilogram (1000 g) of solvent. Molality is also known as molal concentration.

21. Standards and Targets Standards Clear Targets & essential questions
Utilize appropriate mathematical equations and processes to solve chemistry problems.
Identify and solve different types of stoichiometry problems (e.g., volume at STP to mass, moles to mass, molarity).
Convert among the quantities of a substance: mass, number of moles, number of particles, molar volume at STP.
Determine the molarity (M) of a solution.
Determine the molality (m) of a solution.
Analyze a graph to determine the effects of concentration on solutions.
Construct an appropriate graphical relationship for a data set.
How is solubility of a solution expressed?
What factors affect solubility?
How do you calculate the molarity of a solution?
What are the three colligative properties of a solution?
How does molality relate to colligative properties?
In what ways are molarity and molality different? Similar?

23. Heterogeneous Aqueous Systems
A suspension is a mixture from which particles settle out upon standing.
A suspension differs from a solution because the particles of a suspension are much larger and do not stay suspended indefinitely.
Suspensions are heterogeneous because at least two substances can be clearly identified.

24. Heterogeneous Mixtures
A colloid is a heterogeneous mixture containing particles that range in size from 1 nm to 1000 nm. (don’t settle)
The particles in a colloid are spread throughout the dispersion medium.
Colloids have particles smaller than those in suspensions and larger than those in solutions.

25. Colloids
The scattering of visible light by colloidal particles is called the Tyndall effect.
Particles in colloids and suspensions reflect or scatter light in all directions. Solutions do not scatter light.
The chaotic movement of colloidal particles, which was first observed by the Scottish botanist Robert Brown, is called Brownian motion.
Brownian motion is caused by collisions of the molecules of the dispersion medium with the small, dispersed colloidal particles.(why they don’t settle)

26. Colloids
An emulsion is a colloidal dispersion of a liquid in a liquid.
An emulsifying agent is essential for the formation of an emulsion and for maintaining the emulsion’s stability.

27. Standards and Targets Standards Clear Targets & essential questions
Utilize appropriate mathematical equations and processes to solve chemistry problems.
Identify and solve different types of stoichiometry problems (e.g., volume at STP to mass, moles to mass, molarity).
Convert among the quantities of a substance: mass, number of moles, number of particles, molar volume at STP.
Determine the molarity (M) of a solution.
Determine the molality (m) of a solution.
Analyze a graph to determine the effects of concentration on solutions.
Construct an appropriate graphical relationship for a data set.
How is solubility of a solution expressed?
What factors affect solubility?
How do you calculate the molarity of a solution?
What are the three colligative properties of a solution?
How does molality relate to colligative properties?
In what ways are molarity and molality different? Similar?

28. Properties of Solutions
The compositions of the solvent and the solute determine whether a substance will dissolve. The factors that determine how fast a substance dissolves are
stirring (agitation)
temperature
surface area of the dissolving particles
Stirring speeds up the dissolving process because fresh solvent is continually brought into contact with the surface of the solute.
At higher temperatures, the kinetic energy of water molecules is greater.
Greater = faster = more frequent and forceful collisions

29. Properties of Solutions
A spoonful of granulated sugar dissolves more quickly than a sugar cube because the smaller particles in granulated sugar expose a much greater surface area to the colliding water molecules.
A saturated solution contains the maximum amount of solute for a given quantity of solvent at a given temperature and pressure.
An unsaturated solution contains less solute than a saturated solution at a given temperature and pressure.
The solubility of a substance is the amount of solute that dissolves in a given quantity of a solvent at a specified temperature and pressure to produce a saturated solution.
Solubility is often expressed in grams of solute per 100 g of solvent.

30. Standards and Targets Standards Clear Targets & essential questions
Utilize appropriate mathematical equations and processes to solve chemistry problems.
Identify and solve different types of stoichiometry problems (e.g., volume at STP to mass, moles to mass, molarity).
Convert among the quantities of a substance: mass, number of moles, number of particles, molar volume at STP.
Determine the molarity (M) of a solution.
Determine the molality (m) of a solution.
Analyze a graph to determine the effects of concentration on solutions.
Construct an appropriate graphical relationship for a data set.
How is solubility of a solution expressed?
What factors affect solubility?
How do you calculate the molarity of a solution?
What are the three colligative properties of a solution?
How does molality relate to colligative properties?
In what ways are molarity and molality different? Similar?

31. Mixing it Up
Some liquids combine in all proportions, while others don’t mix at all.
Two liquids are miscible if they dissolve in each other in all proportions.
Two liquids are immiscible if they are insoluble in each other.
Temperature affects the solubility of solid, liquid, and gaseous solutes in a solvent
Both temperature and pressure affect the solubility of gaseous solutes.
The solubility of most solid substances increases as the temperature of the solvent increases.
The solubilities of most gases are greater in cold water than in hot.
Gas particles move less, so less likely to escape

32. It’s a bird. It’s a plane. It’s Supersaturated!
A supersaturated solution contains more solute than it can theoretically hold at a given temperature.
The crystallization of a supersaturated solution can be initiated if a very small crystal, called a seed crystal, of the solute is added.
Excess solute crystallizes rapidly.
A supersaturated solution is clear before a seed crystal is added.
Crystals begin to form in the solution immediately after the addition of a seed crystal.

33. Vapor – Pressure Lowering
In a pure solvent, equilibrium is established between the liquid and the vapor.
In a solution, solute particles reduce the number of free solvent particles able to escape the liquid. Equilibrium is established at a lower vapor pressure.

34. The decrease in a solution’s vapor pressure is proportional to the number of particles the solute makes in solution.
Three moles of glucose dissolved in water produce 3 mol of particles because glucose does not dissociate.
Three moles of sodium chloride dissolved in water produce 6 mol of particles because each formula unit of NaCl dissociates into two ions.
Three moles of calcium chloride dissolved in water produce 9 mol of particles
because each formula unit of CaCl2 dissociates into three ions.

35. Boiling – Point Elevation
The difference in temperature between the boiling point of a solution and the boiling point of the pure solvent is the boiling-point elevation.
The same antifreeze added to automobile engines to prevent freeze-ups in winter, protects the engine from boiling over in summer.
The magnitude of the boiling-point elevation is proportional to the number of solute particles dissolved in the solvent.
The boiling point of water increases by 0.512°C for every mole of particles that the solute forms when dissolved in 1000 g of water.

36. Freezing – Point Depression
The difference in temperature between the freezing point of a solution and the freezing point of the pure solvent is the freezing-point depression.
The magnitude of the freezing-point depression is proportional to the number of solute particles dissolved in the solvent and does not depend upon their identity.
The freezing-point depression of aqueous solutions makes walks and driveways safer when people sprinkle salt on icy surfaces to make ice melt. The melted ice forms a solution with a lower freezing point than that of pure water.
Check for Understanding
What is the decrease in vapor pressure when a solute is added to a liquid is due to?
Reduced number of free solvent particles.
Colligative properties depend on ___________________________ and not their identity.
Amount/number

37. Standards and Targets Standards Clear Targets & essential questions
Utilize appropriate mathematical equations and processes to solve chemistry problems.
Identify and solve different types of stoichiometry problems (e.g., volume at STP to mass, moles to mass, molarity).
Convert among the quantities of a substance: mass, number of moles, number of particles, molar volume at STP.
Determine the molarity (M) of a solution.
Determine the molality (m) of a solution.
Analyze a graph to determine the effects of concentration on solutions.
Construct an appropriate graphical relationship for a data set.
How is solubility of a solution expressed?
What factors affect solubility?
How do you calculate the molarity of a solution?
What are the three colligative properties of a solution?
How does molality relate to colligative properties?
In what ways are molarity and molality different? Similar?

38. Mole Fraction
The mole fraction of a solute in a solution is the ratio of the moles of that solute to the total number of moles of solvent and solute.
In a solution containing nA mol of solute A and nB mol of solvent B (XB), the mole fraction of solute A (XA) and the mole fraction of solvent B (XB) can be expressed as follows.

39. Calculations Involving Colligative Properties for Non-Ionic Solutions
Freezing – Point Depression Calculations
Boiling – Point Elevation Calculations
The constant, Kb, is the molal boiling-point elevation constant, which is equal to the change in boiling point for a 1-molal solution of a nonvolatile molecular solute.
The magnitudes of the freezing-point depression and the boiling-point elevation of a solution are directly proportional to the molal concentration (m), when the solute is molecular, not ionic.
The constant, Kf, is the molal freezing-point depression constant, which is equal to the change in freezing point for a 1-molal solution of a nonvolatile molecular solute.
What is the difference between a molecular and ionic solution?
Molecular doesn’t break up into ions.
Nonvolatile – doesn’t evaporate quickly.

40. Calculations Involving Colligative Properties for Ionic Solutions
Boiling – Point Elevation Calculations
When ionic solutes dissolve, the individual ions dissociate in solution.
The amount of ions must be factored into the calculation of freezing point depression.
This amount is referred to as the van’t Hoff factor and is represented in equations as i.
Tf = Kf x im
Freezing – Point Depression Calculations
When ionic solutes dissolve, the individual ions dissociate in solution.
The amount of ions must be factored into the calculation of boiling – point elevation.
The greater the amount of ions in solution, the greater the effect on the BP elevation, FP depression and VP lowering.
Tb = Kb x im

41. Kf Values for Common Solvents
Kb Values for Common Solvents

42. Standards and Targets Standards Clear Targets & essential questions
Utilize appropriate mathematical equations and processes to solve chemistry problems.
Identify and solve different types of stoichiometry problems (e.g., volume at STP to mass, moles to mass, molarity).
Convert among the quantities of a substance: mass, number of moles, number of particles, molar volume at STP.
Determine the molarity (M) of a solution.
Determine the molality (m) of a solution.
Analyze a graph to determine the effects of concentration on solutions.
Construct an appropriate graphical relationship for a data set.
How is solubility of a solution expressed?
What factors affect solubility?
How do you calculate the molarity of a solution?
What are the three colligative properties of a solution?
How does molality relate to colligative properties?
In what ways are molarity and molality different? Similar?