Name: __________________________________________ Date: ________________ Period: ____

REVIEW Unit 4 Test (Chp 4): Aqueous Reactions and Solution Stoichiometry

Multiple Choice (20 questions) (50% of score)

polyatomic ions (names, charges, formulas)

6 strong acids (what does it mean to say a “strong” “acid” ?)

strong bases (group I and Ca, Ba, Sr with hydroxide, OH–) (what is a “strong” “base” ?)

electrolytes (strong, weak, non) (and what particles are actually in solution)

ALWAYS soluble ions (Group I , NH4+ , NO3

–)

NET ionic equations (comp – diss – cross – net – bal)

oxidation numbers of elements in compounds (like what is the ox. # of C in oxalate ion C2O42– ?)

redox reactions (LEO says GER)

activity of metals (which metals are least active – or – which metals do not lose electrons as easily)

gas forming reactions ( ____ reacted with ____ will form which gas: H2(g) or CO2(g) )

solution stoichiometry with Molarity ( L g ) ( g L ) ( g and L M ) ( dilutions M1V1 = M2V2 )

Free Response (32 points) (3 questions) (50% of score)

1) lab question: solution preparation, gravimetric analysis of precipitate to find % by mass (8 pts)

2) lab question: qualitative analysis of unknown solutions by precipitation (9 pts)

3) write 3 NET ionic equations from verbal descriptions, predict products, and balance (15 pts)

Section I Multiple Choice1

NO Calculator Allowed

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CsS

lithium hydroxide

ammonium sulfate

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Pb(NO3)2 (aq)

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What is/are the spectator ion(s) in the reaction between BaI2(aq) and Na2SO4(aq)?

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6

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How many grams of methanol, CH3OH (MW = 32.0 g∙mol–1) are there in 500. mL of a 0.500 M CH3OH solution?

27. Beaker X and beaker Y each contain 1.0 L of solution, as shown above. A student combines the solutions by pouring them into a larger, previously empty beaker Z and observes the formation of a white precipitate.Assuming that volumes are additive, which of the following sets of solutions could be represented by the diagram above?

Beaker X Beaker Y Beaker Z(A) 2.0 M AgNO3 2.0 M MgCl2 4.0 M Mg(NO3)2 and AgCl(s)(B) 2.0 M AgNO3 2.0 M MgCl2 2.0 M Mg(NO3)2 and AgCl(s)(C) 2.0 M AgNO3 1.0 M MgCl2 1.0 M Mg(NO3)2 and AgCl(s)(D) 2.0 M AgNO3 1.0 M MgCl2 0.50 M Mg(NO3)2 and AgCl(s)

Section II Free ResponseCalculator Allowed

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CLEARLY SHOW THE METHODS USED AND STEPS INVOLVED IN YOUR ANSWERS. It is to your advantage to do this, because you may earn partial credit if you do and little or no credit if you do not. Attention should be paid to significant figures.

1. A student is assigned the task of preparing 50. mL of 6 M HNO3 to use in an experiment.

(a) The student is provided with a stock solution of 16 M HNO3 , two 100 mL graduated cylinders that can be read to ±1 mL, a 100 mL beaker that can be read to ±10 mL, safety goggles, rubber gloves, a glass stirring rod, a dropper, and distilled H2O.

(i) Calculate the volume, in mL, of 16 M HNO3 that the student should use for preparing 50. mL of 6 M HNO3 . (1)

(ii) Briefly list the steps of an appropriate and safe procedure for preparing the 50. mL of 6 M HNO3. Only materials selected from those provided to the student (listed above) may be used. (2)

(iii) Explain why it is not necessary to use a volumetric flask (calibrated to 50.00 mL ±0.05 mL) to perform the dilution. (1)

In a second experiment, a student is given 2.94 g of a mixture containing anhydrous MgCl2 and KNO3. To determine the percentage by mass of MgCl2 in the mixture, the student uses excess AgNO3(aq) to precipitate the chloride ion as AgCl(s).

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(b) Starting with the 2.94 g sample of the mixture dissolved in water, briefly describe the steps necessary to quantitatively determine the mass of the AgCl precipitate. (2)

(c) The AgCl precipitate is filtered, washed, dried, and weighed to constant mass in a filter crucible. The student determines the mass of the AgCl precipitate to be 5.48 g. On the basis of this information, calculate each of the following.

(i) The number of moles of MgCl2 in the original mixture (2)

(ii) The percent by mass of MgCl2 in the original mixture (1)

2. The identity of an unknown solid is to be determined. The compound is one of the seven salts in the following table.

Al(NO3)3•9H2O Ba(OH)2•8H2O CaCO3 CuSO4•5H2O

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NaOH BaSO4 Ni(NO3)2•6H2O

Use the results of the following observations or laboratory tests to explain how each compound in the table may be eliminated or confirmed. The tests are done in sequence from (a) through (e).

(a) The unknown compound is white. In the table below, cross out the two compounds that can be eliminated using this observation. Be sure to cross out these same two compounds in the tables in parts (b), (c), and (d). (2)

Al(NO3)3•9H2O Ba(OH)2•8H2O CaCO3 CuSO4•5H2O

NaOH BaSO4 Ni(NO3)2•6H2O

(b) When the unknown compound is added to water, it dissolves readily. In the table below, cross out the two compounds that can be eliminated using this test. Be sure to cross out these same two compounds in the tables in parts (c) and (d). (2)

Al(NO3)3•9H2O Ba(OH)2•8H2O CaCO3 CuSO4•5H2O

NaOH BaSO4 Ni(NO3)2•6H2O

(c) When AgNO3(aq) is added to an aqueous solution of the unknown compound, a white precipitate forms. In the table below, cross out one compound that can be eliminated using this test. Be sure to cross out the same compound in the table in part (d). (1)

Al(NO3)3•9H2O Ba(OH)2•8H2O CaCO3 CuSO4•5H2O

NaOH BaSO4 Ni(NO3)2•6H2O

(d) When the unknown compound is carefully heated, it loses mass. In the table below, cross out one compound that can be eliminated using this test. (1)

Al(NO3)3•9H2O Ba(OH)2•8H2O CaCO3 CuSO4•5H2O

NaOH BaSO4 Ni(NO3)2•6H2O (e) Describe a test that can be used to confirm the identity of the unknown

compound identified in part (d). Limit your confirmation test to a reaction between an aqueous solution of the unknown compound and an aqueous solution of one of the other soluble salts listed in the tables above. Describe the expected results of the test; include the formula(s) of any product(s).

3. For each of the following three reactions, in part (i) write a balanced equation for the reaction with coefficients in terms of lowest whole numbers, and in part (ii) answer the question about the reaction. Assume that solutions are aqueous unless otherwise indicated. Represent substances in solution as ions if the substances are extensively ionized. Omit formulas for any ions or molecules

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that are unchanged by the reaction. You may use the empty space for scratch work, but only equations that are written in the answer boxes provided will be graded.

(a) A solution of barium hydroxide is added to a solution of acetic acid (ethanoic acid).

(i) Balanced equation: (4)

(ii) Which substance is a weak electrolyte. Explain. (1)

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(b) A solution of potassium sulfide is added to a solution of iron(III) chloride.

(i) Balanced equation: (4)

(ii) Classify this reaction in two ways. (1)

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(c) Excess nitric acid is added to solid sodium bicarbonate.

(i) Balanced equation: (4)

(ii) If this reaction takes place in a rigid sealed container, what change (if any) is observed in the pressure inside the container? (1)

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ANSWER KEY

1. 2011 #2(a) (dilution)

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2008 #2(d)(e) (gravimetric analysis)

2. 2006B #8(a) (edited)

3. 2008B #5

4. (a)NH4+ b/c it donates a proton (H+) (Bronsted-Lowry)

(b)precipitation, double replacement(c)pressure increases due to gas produced in reaction.

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