Note: This "practice quiz" is for Unit 4 and for preparing for Exam 1 on 1/13/98. There is no e-mail activity for Unit 4 but you will be given a longer 50 point quiz to turn in next week. Quizzes turned in by Wednesday evening, 2/11 will be returned in the "Return Box" on Thursday morning so you can get them to study for the test ----MD

Unit 4 Questions:

1. a) Calculate the molartiy, M, of each of these solutions: (See Problem 15 Workbook)

i) 5.65 grams of sodium bicarbonate, NaHCO3 dissolved in enough water to make 250 mls of solution.

ii) 185 grams of sucrose, C12H22O11 dissolved in enough water to make 750.0 mls of solution.

iii) 60 grams of potassium hydroxide, KOH dissolved in enough water to make 1.25 liters of solution.

b) How many grams of potassium sulfate, K2SO4 (MW = 174.2 gms/mol) are needed to prepare 500.0 mls of a 0.65 M solution of potassium sulfate ?

c) How many grams of silver nitrate, AgNO3 ( MW = 170 gm/mol ) are needed to prepare 250.0 mls of a 0.025 M solution of silver nitrate ?

2 What volume of 0.135 M NaOH in milliliters, contains 35.0 grams of sodium hydroxide ? (See Problem 17 Workbook)

3. For each solution, tell what ions exist in solution and give the molar concentration cations and anions in each case: (See Problem 20 Workbook)

a) 0.60 M CaCl2, for example dissocates in water to give 0.60 M Ca 2+ (aq) ion and 2x0.60M or 1.20 M Cl - (aq) ion.

b) 1.50 M NaOH

c) 0.375 M K2Cr2O7 ( Check page 118, Table 3.2 Polyatomic Ions if you are unsure about the anion or cations that might be formed. Also, you should verify that all the "salts" in these problems are soluble by referring to the solubility tables on page 167.)

d) 0.500 M NH4(CH3CO2)

e) 0.500 M (NH4)2SO4, ammonium sulfate.

4.Given the reaction:

Na2CO3 (s) + 2 HNO3 (aq) = 2 NaNO3 (aq) + CO2 (g) + H2O (l)

a) Is the reaction balanced ? Is this a redox reaction ? If so, what species is oxidized ? reduced ?

b) How many grams are needed to completely react with 50.00 mls of 0.375 M HNO3 (aq), nitric acid ?

c). How many grams of carbon dioxide gas will be formed from the reaction in part (a) ?

General Review of Units 1 to 4

1. a) How many neutrons are in a chromium- 52 ( Cr - atomic mass 52 ) nucleus ?

b). What is the symbol and name of the element whose nucleus contains 25 protons and 25 neutrons ?

c) Would an isotope of the element in (b) contain 25 protons and 27 neutrons or 27 protons and 25 neutrons ? Briefly explain.

2. Given the mass -23 isotope of sodium containing 11 protons,12 neutrons and 11 electrons, what would be the numbers of " p, n and e " in the sodium cation, Na+ ?

3. a) What is the molecular weight of methanol, CH3OH ?

b) How many grams are in 5.75 moles of methanol ?

c) How many moles of methanol are in 400 grams of it?

4. Balance the following equation by inspection:

____ CuS (s) + _____ O2 (g) = ____ Cu (s) + ____ SO2 (g)

b) Is this a redox reaction ? If so, what element is oxidized ? reduced ? and identify the oxidizing agent and the reducing agent.

c) If 100 grams of copper (II) sulfide, CuS is mixed with 50 grams of oxygen, what is the limiting reactant?

d) What is the theoretical yield of copper, Cu from the reaction mixture in (c) ?

e) If the actual yield of copper was found to be 53.5 grams. what was the percent yield of this reaction?

5. In each case, determine whether the ionic compound is expected to be soluble in waster. If it is, indicate what solvated ions would be formed.

a) Is copper(II)sulfide, CuS ? (Check text page 167 )

b) Is ammonioum acetate, NH4(CH3CO2) ?

c) Is calcium carbonate, CaCO3 ?

d) Is potassium carbonate, K2CO3 ?

e) In general, what "carbonates" are soluble in water ?

f) If you mix an aqueous solution of potassium carbonate, K2CO3 (aq) with calcium nitrate, Ca(NO3)2 (aq) will a precipitate form? Think about your responses to (c), (d) and (e) above.

Practice Quiz Answers .

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