The Chemistry of Solutions Page | 1

Unit 7: The Chemistry of Solutions

(Link to Prentice Hall Text: Chapters 17 & 18)

Name:______

Date Due / Assignments / Page Number: Problem Numbers
Assignment 1: Solution Properties / 496: 33, 35, 36, 37, 38
Assignment 2: Temperature & Pressure / 528: 43 – 47, 75, 78
Assignment 3: Solution Concentration / 528: 52-56
Assignment 4: Colligative Properties / 528: 57-60, 62, 68, 69. 73, 79
  1. What is a Solution?

Solution Properties

The human body is largely a system of solutions. The correct solution concentrations are necessary to maintain life.

A solution is a homogeneous mixture.

  1. A Solution Has Two Parts

Solute-

Solvent-

  1. Properties of Solution
  1. Clear
  2. A solid will not settle out of the solution when it stands
  3. Will pass through a piece of filter paper
  4. Electrolytes in Solution:
  1. Non-electrolytes in Solution:
  1. Energy Changes During Solution Formation
  1. Endothermic
  1. Exothermic
  1. Classification of Solutions:
  1. Saturated solution:

-A saturated solution represents an equilibrium:

  1. Unsaturated solution:
  1. Supersaturated solution:

Solute / Solvent / Example
solid / solid
solid / liquid
gas / solid
liquid / liquid
gas / liquid
gas / gas

Dissociation/ Dissolution/ Solvation Equations

When a soluble ionic compound is placed in water the ionic substance or salt will dissociate into its component ions.

Ex. SrCl2 Sr2+ + 2Cl-

Write the dissociation equation for the following soluble ionic compounds.

The Chemistry of Solutions Page | 1

1. NaCl (s)

2. Al(C2H3O2)3 (s)

3. Ba(OH)2 (s)

4. CoSO4 (s)

5. Be(NO3)2 (s)

6. K3PO4 (s)

7. (NH4)2S (s)

8. Li2CrO4 (s)

9. Cs2CO3 (s)

10. Sodium hydroxide

11. Ammonium acetate

12. Calcium chloride

13. Iron(III) sulfate

14. Manganese (III) carbonate

15. Zinc chlorite

16. Aluminum iodide

The Chemistry of Solutions Page | 1

  1. Factors that affect solubility?

Molecular Identity Affects Solubility - Polarity

A solute dissolves in a solvent that has a similar polarity, such that positives and negatives can attract.

Rule of Thumb: Like molecules dissolve like molecules.

Solute Type / Nonpolar Solvent / Polar Solvent
Nonpolar / soluble / insoluble
Polar / insoluble / soluble
Ionic / insoluble / soluble

Polarity Practice (Remember: Polar molecules are asymmetrical!)

Formula / Lewis Structure / Polar? / Soluble in Water or Carbon Tetrachloride?
CO2
CH3Cl
H2O
NH3
CaCl2
NaCl
I2

Modified Table G

1. At what temperature will 100g of water dissolve 60g of NH4Cl in a saturated solution?

2.How much ammonium chloride can be dissolved in 100 grams of water at 80 OC?

3. How much NH4Cl can be dissolved in 350 grams of H2O at 70 oC?

4. How much NH4Cl can dissolve in 45 grams of water at 30 oC?

Temperature Affects Solubility (Table G)

  1. Affect on solids:
  1. Affect on gases:

Practice Reading Table G

  1. What is the solubility of KClO3 at 50°C?______
  2. Which is most soluble at 15°C: KNO3, NaCl, or NH4Cl?______
  3. How many grams of KNO3 are needed to saturate 50.0g of water at 70°C?______
  4. Which compound’s solubility decreases most rapidly when the temperature increases from 50°C to 70°C?______
  5. What compound is most soluble at 20°C?______
  6. Which compound is least soluble at 80°C?______
  7. How many grams of sodium nitrate must be added to 100 mL of water to produce a saturated solution at 50°C?______
  8. A saturated solution of potassium chlorate is made at 10°C by dissolving the correct mass of salt in 100 mL of water. When the solution is heated to 90°C, how many grams must be added to saturate the solution?______
  9. At what temperature do saturated solutions of sodium chloride and potassium chloride contain the same mass of solute per 100 mL of water?______
  10. A saturated solution of potassium nitrate is prepared at 60°C using 200 mL of water. If the solution is cooled to 30°C, how many grams will precipitate out of solution?______

Pressure Affects the Solubility of a Gas in Solution

As the pressure above a liquid increases, more and more gas can be dissolved in solution. This is why soda cans and bottles are pressurized – the increased pressure allows more carbon dioxide to be dissolved in solution.

Molecular Identity Affects Solubility – Ionic Salts (Table F)

Regents Solubility Rules

Honors Solubility Rules

Are the following compounds soluble (S) or insoluble (I)?

1. NaCl ______2. Fe(ClO3) ____3. CaSO4 _____4. NH4OH_____5. Ba3(PO4)2 ___6. MgCrO4 _____7. SrCO3 ______

8. K2S ______9. PbCl2 ______10. Fe(C2H3O2)3___ 11. Cs3PO4 ______12. Zn(OH)2 ____ 13. Na2S ______14. CaCO3____

15. AgCl ______16. MnCrO4 ____17. MgHCO3 ______18. Be(NO3)2_____19. FeSO4 ______20. CuOH ______21.Ag2CrO4 ______

Double Replacement Reactions:

Double replacement reactions that involve aqueous solutions only take place of a solid or precipitate are formed. They can be represented in the three different ways.

1. Molecular equation -

2. Complete ionic equation -

3. Net ionic equation -

Spectator Ions -

Example:

___CoCl2 (aq) + ___Na2S (aq) 

Complete IE

Net IE:

Writing Net Ionic Equations using Table F

Net Ionic equations only include the species that changed during the reaction. The ions that did not change are called spectator ions. Write balanced molecular, complete ionic and net ionic equations for the following reactions.

  1. ___CaCl2(aq) + ___Na2S (aq)

Complete IE:______

Net IE: ______

  1. ___NaBr (aq) + ___AgNO3(aq)

Complete IE:______

Net IE: ______

  1. ___BeSO4(aq) + ___Pb(NO3)2 (aq) 

Complete IE:______

Net IE: ______

  1. ___Ba(NO3)2 (aq) + ___K2SO4 (aq)

Complete IE:______

Net IE: ______

  1. ___FeCl3 (aq) + ___KOH (aq) 

Complete IE:______

Net IE: ______

  1. Measuring Solution Concentrations

Units of Concentration Measurement

Molarity
Units:
Percent by Mass
Units:
Parts per Million
Units:
Percent by Volume
Units:
Mole Fraction
Units:
Molality
Units:
Molarity

Units:
Percent by Mass

Units:
Parts per Million

Units:
Percent by Volume

Units:
Mole Fraction

Units:
Molality

Units:

General Practice with Concentration of Solutions

  1. What is the molarity of a solution containing 82.0 g of Ca(NO3)2 in 2.0 L of solution?
  1. What is the molarity of a KF(aq) solution containing 116 g of KF in 1.00 L of solution?
  1. What is the molarity of a H2SO4 solution if 0.25 L of the solution contains 0.75 mol of H2SO4?
  1. What is the percent by mass of a solution if 60.0g of acetic acid are added to 90.0g of water?
  1. What is the percent by mass of a solution in which 60.0g of NaOH are dissolved in sufficient water to make 100g of solution?
  1. Carbon dioxide gas has a solubility of 0.0972 g/100 g H2O at 40°C. What is the concentration expressed in parts per million?
  1. If 70.0 mL of isopropyl alcohol is combined with 30.0 mL of water, what is the percent volume of the solution?
  1. How many grams of water must be used to dissolve 100 grams of sucrose C12H22O11 to prepare a 0.2 mole fraction of sucrose in the solution?
  1. Determine the mole fraction concentration of glucose in a solution in which 320 grams of glucose C6H12O6 are dissolved in 4000 grams of water.
  1. How many grams MgCl2 will be added to 1000 grams of water to prepare a 0.1 mole fraction in MgCl2?
  1. Vanillin (C8H8O3) is a flavoring agent. A 37.2 g sample of vanillin was dissolved in 168.5 g of diphenyl ether. What is the molality of the solution?
  1. 49.8 grams of KI is dissolved in 1.00 kg of solvent. What is the molality?
  1. Determine the molal concentration of a solution in which 320 grams of glucose C6H12O6 are dissolved in 4000 grams of water.
  1. Suppose that 0.25 molal solution of sugar. How many moles of sugar are dissolved if you have 1.2 kg of water?
  1. Calculate the mole fraction of HCl in an aqueous hydrochloric acid solution containing 36% hydrochloric acid by weight.
  1. A .380 M solution of glucose (C 6H12O6 ). How many grams of glucose were dissolved if you had a 500. mL solution?
  1. Determine the mole fraction of KCl in 3000 grams of aqueous solution containing 37.3 grams of potassium chloride KCl.
  1. 75.4 g of cobalt (II)nitrate is added to enough water to make a 4.5 L solution. What is the molarity of the solution?
  1. How many grams of magnesium bromide would have to be added to 400.g water solution at a molality of 1.50 m?

The Dilution Equation

Making New Solutions

The amount of solute is constant when a solution is diluted. The concentration of the new solution can be determined using the following formula:

The Dilution Equation
M1V1 = M2V2
Where M1 and V1 are the molarity and volume of the original solution, and M2 and V2 are the molarity and volume of the final solution.

Practice with Diluting Solutions

  1. How many milliliters of 18 M hydrochloric acid will be needed to make a dilution of a 1.0 L solution of 2.0 M hydrochloric acid?
  1. You need a 4.0 L solution of 0.10 M sodium hydroxide. How many milliliters of concentrated 6.0 M solution will you need to make the dilution?
  1. How many mL of water must be added to 65 mL of a 5.5M solution of NaOH in order to prepare a 1.2 M solution of NaOH?
  1. What is the molarity of a solution of NaCl if 68 mL of a 4.5 M solution is diluted to 145 mL?
  1. What is the molarity of a solution that contains 30.0 grams of NaOH in 500. milliliters of solution?
  1. To what final volume should 11.9 mL of an 8.00 M acetic acid solution be diluted to obtain a 1.50 M solution?
  1. What volume of a 5.75 M formic acid solution should be used to prepare 2.0 L of a 1.0 M formic acid solution?
  1. What is the molarity of a solution of ammonium chloride prepared by diluting 50.0 mL of 3.79 M ammonium chloride solution to 2.0 L?

Practice with Colligative Properties of Solutions

  1. How many species would form in solution when the following salts dissolve? Which of these solids would cause the greatest colligative property effect?

(1)NaCl(s) i =

(2)CaCl2 (s) i =

(3)C6H12O6 (s) i =

(4)Na3PO4(s) i =

  1. The vapor pressure of pure water at 110°C is 1070 torr. A solution of ethylene glycol and water has a vapor pressure of 1.00 atm at 110°C. Assuming that Raoult’s Law is obeyed, what is the mole fraction of ethylene glycol in the solution?
  1. If I add 45 grams of sodium chloride to 500 grams of water, what will the melting and boiling points be of the resulting solution? (Kb = 0.52 0C/m and Kf= 1.86 0C/m).
  1. Which concentration of a solution of CH3OH in water has the lowest freezing point?

(1)0.1 M

(2)0.01 M

(3)0.001 M

(4)0.0001 M

  1. A 1 kilogram sample of water will have the highest freezing point when it contains

(1)1 × 1017 dissolved particles

(2)1 × 1019 dissolved particles

(3)1 × 1021 dissolved particles

(4)1 × 1023 dissolved particles

  1. Which solution will have a higher boiling point: A solution containing 105 grams of sucrose (C12H22O11) in 500 grams of water or a solution containing 35 grams of sodium chloride in 500 grams of water?
  1. A solution was prepared by dissolving 0.915 g of sulfur, S8, in 100.0 g of acetic acid, HC2H3O2. Calculate the freezing point and boiling point of the solution. (Kf = 3.63°C/m, Tf = 16.6°C, Kb = 3.22°C/m, Tb = 117.9°C)
  1. Ethylene glycol (HOCH2CH2OH) is a low volatility liquid commonly sold as antifreeze to be mixed with water in car radiators. By adding a nonvolatile solute to the water in the radiator, not only is the freezing point of the resulting solution substantially lower than the freezing point of water, the boiling point is raised substantially. Thus a water/ethylene glycol mixture protects the radiator both from freezing and from boiling over. Calculate the freezing and boiling points of a mixture of water and ethylene glycol obtained by mixing 2.00 kg ethylene glycol (M.W. = 62.0682 g/mol) and 2.00 kg of water. (Kf =1.86°C/m, Kb = 0.52°C/m)

Solution Stoichiometry – Putting it All Together

  1. A chemist dissolved 25.0 grams of sodium carbonate to make a 125.9mL aqueous solution in Beaker A, and 25.0 grams of copper (II) chloride in 125.9 mL of water in Beaker B and then combines the two solutions in Beaker C.

(a)Write a balanced chemical reaction for the reaction that takes place in Beaker C.

(b)Calculate the molarity of the solution of sodium carbonate.

(c)Calculate the molarity of the solution of copper (II) chloride.

(d)Identify the limiting reactant and the excess reactant.

(e)Calculate the theoretical mass of the precipitate that should form in solution.

  1. A chemist combined 15.0 mL of 0.25M sodium hydroxide solution with 28.0 mL of 0.10M lead (II) nitrate solution. Identify the limiting reactant and the excess reactant and calculate the theoretical mass of the precipitate that should form is solution.
  1. A chemist combined 0.30 grams of zinc metal with 50.0 mL of 3.0 M hydrochloric acid.

(a)Calculate the mass of zinc chloride which could be collected after evaporating the remaining solution to dryness.

(b)Calculate the volume of hydrogen gas which should be released if the experiment is done at STP.

  1. If 30.0 mL of 0.80M nickel (II) chloride solution is combined with 15.0 mL of 3.0M phosphoric acid (H3PO4), how many grams of precipitate should form?
  1. If 50.0 g of sodium carbonate is reacted with 75.0mL of 3.0M copper (II) chloride, calculate the mass of solid product.