24

Chemistry 6.0 Name______

Solutions

Solubility

1.  Use the solubility curves above to answer the following questions:

a.  Which salt is least soluble at 20°C?

b.  How many grams of potassium chloride can be dissolved in 200g of water at 80°C?

c.  At 40°C, how much potassium nitrate can be dissolved in 300 g of water?

d.  Which salt shows the least change in solubility?

e.  A solution at 30°C contains 90g of sodium nitrate in 100g of water. Is this solution saturated, unsaturated, or supersaturated?

f.  How many grams of potassium chlorate will crystallize when a saturated solution is cooled from 80°C to 50°C?

g.  How many grams of potassium chlorate are needed to saturate 10 g of water at 30°C?

h.  Describe what will happen to an ammonia solution as it is slowly heated.

i.  Describe what will happen when 80g of potassium nitrate is added to 100g of water at 40°C and stirred.

j.  A solution containing 20g of ammonium chloride dissolved in 50g of water at 100°C is slowly cooled. At what temperature will the solution begin to crystallize?

k.  List 2 chemicals from the graph that would be more soluble at higher pressures.

l.  List 2 chemicals from the graph whose solubility is unaffected by pressure.

2.  Describe what would happen to a small crystal of the solute that is added to a solution of that solute that is:

a.  Saturated –

b.  Unsaturated –

c.  Supersaturated –

3.  Draw the structures of each of the following and indicate if the chemical will likely be soluble or insoluble in water:

a.  CO2

b.  carbon tetrachloride

c.  phosphorus trichloride

Dilutions

4.  What volume of concentrated 18 M sulfuric acid is needed to prepare 250 mL of a 6.0 M solution?

5.  If 14.6 mL of water were added to 25.0 mL of a 0.100 M acetic acid solution, what molarity would the solution become?

6.  To what volume should 25 mL of 15 M nitric acid be diluted to prepare a 3.0 M solution?

7.  To how much water should 50. mL of 12 M hydrochloric acid be added to produce a 4.0 M solution?

8.  Describe how to prepare 100.mL of a 0.500 M NaOH solution beginning with a 3.00M NaOH stock solution.

9.  Describe how to prepare 100.mL of a 0.500 M NaOH solution beginning with solid NaOH.

Ionic Equations

10.  Write an E if the indicated substance is an electrolyte or an N if it is a non-electrolyte.

_____ HBr(aq) _____ Na2S _____N2O5 _____KOH _____ CO2

11.  Write appropriate ionization equations or dissociation equations to represent what happens when each of the following chemicals are mixed with water:

  1. HNO3(aq)
  1. H2SO4(aq)
  1. LiOH
  1. Ba(OH)2
  1. Na2SO4

12.  Write molecular, ionic and net ionic equations for each of the following:

  1. Solutions of potassium hydroxide and nitric acid are mixed.
  1. Solutions of barium chloride and sodium sulfate are mixed.
  1. Solid calcium oxide is added to a hydrochloric acid solution
  1. Solutions of lithium acetate and copper(II) nitrate are mixed.
  1. Solutions of iron(III) bromide and ammonium carbonate are mixed
  1. A piece of zinc metal is added to a solution of copper(II) sulfate.
  1. Solid lead(II) nitrate crystals are sprinkled into a solution of rubidium iodide.
  1. A piece of aluminum metal is added to a solution of silver nitrate.

Determining ∆H From Calorimetry

Assume that the density and specific heat of all solutions are the same as water.

13.  When 12.8 g of KCl dissolves in 75.0 g of water in a calorimeter, the temperature drops from 31.0°C to 21.6°C. Write the equation for this process and calculate the ΔH in kJ/mol.

14.  Silver chloride can be precipitated by adding solid silver nitrate to a sodium chloride solution. If 0.956 g of silver nitrate is added to 21.0 mL of a 1.0 M sodium chloride solution, the temperature increases from 25.0°C to 27.58°C.

a.  Calculate the ΔH for this process.

b.  Write the net ionic, thermochemical equation for this reaction.

c.  Draw an energy diagram for this reaction.

d.  Calculate the enthalpy change for this reaction that is required to precipitate 3.55 g of silver chloride.

15.  When 25.7 g of NaI dissolves in 80.0 g of water in a calorimeter, the temperature rises from 20.5°C to 24.4°C. Calculate the enthalpy change in kJ/mol.

16.  When 16.9 g of NaOH reacts with 50.0 g of an HCl solution, the temperature rises from 22.4°C to 31.0°C. Assume the NaOH is the limiting reagent.

a.  Calculate ΔH

b.  In a separate experiment, 35.8 g of NaOH is reacted with HCl. The heat released is applied to a block of ice at 0°C. How many grams of the ice will melt?

17.  When 19.2 g of KCN dissolves in 65.0 g of water, the temperature drops from 28.1°C to 15.4°C. Write the thermochemical equation for this process.

18.  Answer the questions below using the 3 given equations:

Reaction 1: 2 Na + H2SO4 à Na2SO4 + H2 DH = -577.5 kJ

Reaction 2: Na + H2O(l) à NaOH + ½ H2 DH = ???

Reaction 3: H2SO4 (l) à H2O(l) + SO3(g) DH = ???

a.  Determine the enthalpy change of reaction 2, in kJ/mol, given the following experimental data: When 1.50 g of sodium is placed in a calorimeter containing 40.0 g of water, the temperature increases from 22.0°C to 91.0°C. (Assume the hydrogen produced in the reaction is contained in the calorimeter and that the specific heat of the solution is the same as it is for water).

b.  Determine the enthalpy change of reaction 3 by using the enthalpies of formation.

c.  Apply Hess’s Law to reactions 1, 2, and 3 to determine the enthalpy change for:

2NaOH + SO3 à Na2SO4 + H2O(l)

d.  Write the thermochemical equation for:

  1. Reaction 1:
  1. Reaction 3:

e.  Write the equation for reaction 2 in DH notation.

f.  Is reaction 2 endothermic or exothermic? Cite two reasons for your choice.

g.  In reaction 3, do the reactants or the products have a lower enthalpy?

h.  Draw the energy diagram for:

Reaction 1 Reaction 3

i.  How many kilojoules of thermal energy are transferred when 2.09 L of hydrogen gas at STP is produced in reaction 2?

j.  How many grams of sodium would be required to react in reaction 1 if 127 kJ of thermal energy is released?

Solvent / Formula / Freezing / Boiling / Kf(°C/m) / Kb(°C/m)
Point (°C) / Point (°C)
Water / H2O / 0 / 100 / 1.858 / 0.512
Acetic acid / HC2H3O2 / 16.6 / 118.5 / 3.59 / 3.08
Benzene / C6H6 / 5.455 / 80.2 / 5.065 / 2.61
Camphor / C10H16O / 179.5 / ... / 40 / ...
Cyclohexane / C6H12 / 6.55 / 80.74 / 20 / 2.79

Colligative Properties

19.  Determine the freezing and boiling points of solution consisting of 6.55 g of glucose dissolved in 21.2 g of water.

20.  Determine the freezing and boiling points of a solution consisting of 1.56 g of I2 dissolved in 4.99 g of benzene.

21.  How many grams of sucrose must be dissolved in 150. g of water to prepare a solution that will boil at 100.956oC?

22.  How many grams of camphor must be dissolved in 25.0 g of cyclohexane to prepare a solution that will freeze at 6.04oC?

23.  When 2.65 g of an unknown molecular solid is dissolved in 17.5 g of water, the resulting solution freezes at −1.99oC. Determine the molar mass of the solid.

24.  When 5.04 g of an unknown molecular solid is dissolved in 12.3 g of acetic acid, the resulting solution boils at 120.8oC. Determine the molar mass of the solid.

25.  What is the boiling point of a solution that is formed by dissolving 19.6 grams of barium hydroxide in 115 g of water?

26.  Determine the freezing point of a 14.8 % solution of aluminum chloride.

27.  The soluble product that results from the reaction between 37.3 grams of lead(II) nitrate and 137 mL of 0.800 M sodium phosphate is isolated and dissolved in 2.88 x 1024 molecules of water. What are the freezing and boiling points of this solution? Write the net ionic equation for the reaction.

Acids and Bases

28.  Write the name for the following acids:

a.  HNO3(aq)______b. HBr (aq) ______

c. H2CO3(aq)______d. H2S(aq) ______

e. HNO2(aq)______f. HC2H3O2(aq) ______

29.  Write the formula for the following acids:

a. chloric acid ______b. hydrofluoric acid ______

c. sulfurous acid ______d. carbonic acid ______

e. hydroiodic acid ______f. phosphoric acid ______

30.  Acids react with metals to produce a salt and hydrogen gas. Write net ionic equations for the following:

a.  Na + HCl(aq) →

b.  HBr(aq) + Ba →

c.  Aluminum + nitric acid →

31.  Acids react with bases to produce a salt and water. Write net ionic equations for the following:

a.  HClO4(aq) + NaOH →

b.  H3PO4(aq) + Ca(OH)2 →

c.  Sulfuric acid + lithium hydroxide →

32.  Write the formula for the acid and base required to produce the salt, Cs2CrO4 in a neutralization reaction.

acid:______base:______

Properties of Acids and Bases

33.  Write the appropriate term that fits the description provided.

a.______  An ionic compound formed when an acid reacts with a base.

b.______  The reaction between an acid and a base.

c.______  A substance that conducts an electric current when in solution.

d.______  A proton donor.

e.______  A substance that has different colors in acids and bases.

f.______  A substance that supplies hydroxide ions in solution.

g.______  The removal of a hydrogen ion from an acid.

h.______  The ion formed when a proton is added to a water molecule.

34.  Write A for acid, B for base or an X if the indicated property can apply to either.

_____ feels slippery _____ sour taste

_____ stings in open wounds _____ reacts with most metals

_____ phenolphthalein is colorless _____ litmus paper turns red

_____ does not react with metals _____ methyl orange turns orange

_____ is an electrolyte _____ has a bitter taste

_____ can produce a salt in some reactions _____ has a pH > 7

35.  What is the conjugate acid of:

a. NO2− b. NH3 c. HPO4−2 d. CH3NH2

36.  What is the conjugate base of:

a. H2SeO3 b. HBrO4 c. HPO4−2 d. NH4+

37.  For the following reactions, identify the acid (A), base (B), conjugate acid (CA) and conjugate base (CB)

a.  HNO2 + H2O → H3O+ + NO2−

b.  HCN + H2O → CN− + H3O+

c.  H2O + H2O → H3O+ + OH−

d.  H2O + F- → OH− + HF

e.  NH4+ + H2O → NH3 + H3O+

f.  CO3−2 + H2O → HCO3- + OH−

38.  Explain the following given the equation: NH3 + H2O → NH4+ + OH−

a.  Ammonia is an Arrhenius base:

b.  Ammonia is a Bronsted-Lowry base:

c.  Water is a Bronsted- Lowry acid:

d.  Water is not an Arrhenius acid:

pH

39.  Determine the following quantities for a 0.00045 M HCl solution:

a. [H3O+] b. [OH−] c. pH d. pOH

40.  Determine the following quantities for a 0.0034 M NaOH solution:

a. [H3O+] b. [OH−] c. pH d. pOH

41.  Calculate pH for the following and identify if the solution is acidic, basic or neutral:

a. [H3O+] = 2.9 x 10-9 M b. [OH−] = 1.07 x 10−8 M c. pOH = 12.1

42.  Calculate [H3O+] for the following and identify if the solution in acidic, basic or neutral:

a. [OH−] = 5.0 x 10-3 M b. pH = 3.7

c. pH = 11.2 d. pOH= 6.0

43.  Given the pH values determine the [OH−]. Indicate if acidic, basic or neutral.

a) 7.00 b) 11.35 c) 4.15 d) 5.09

44.  Determine the pH of each solution. Indicate if acidic, basic or neutral.

a) 2.5 x 10−5 M H3O+ b) 4.0 x 10−7 M OH− c) 3.0 x 10−3 M H+

45.  Given the concentration for the following solutions, solve for the [H+] or [OH-]. Indicate if acidic, basic or neutral.

a) 2.9 x 10−7 M H+ b) 4.6 x 10−9 M OH− c) 8.91 x 10-4 M H+

Review

46.  Which of the following will have a higher solubility?

  1. Sugar and water at 50°C or at 25°C?
  2. Carbon dioxide and water at 50°C or 25°C?
  3. Sugar and water at 1.5 atm or 2.5 atm?
  4. Carbon dioxide and water at 1.5 atm or 2.5 atm?

47.  Why will sodium chloride dissolve in methyl alcohol, but not in carbon tetrachloride?

48.  Why does a sugar cube dissolve more slowly than granulated sugar?

49.  Use Lewis structures to determine if the following compounds will be more soluble in water or carbon tetrachloride.

a.  Sulfur dioxide b. Sulfur trioxide

50.  When a crystal of a solid solute is added to a solution containing that solute, the solution begins to crystallize. What kind of solution was it before it crystallized? What kind of solution was it after it crystallized?

51.  How would you prepare the following solutions:

a.  250 mL of 0.500M HCl(aq) from a 12.0 M stock solution

b.  30.0 mL of 2.50 M NaOH from solid NaOH

52.  For each of the following, write complete and balanced molecular, ionic and net ionic equations.