Chapter 4 Test

Question 1

Which of these substances is likely to be the best electrical conductor when one mole is added to a liter of water?

Answer 1

MgCl2

Question 2

Suppose you have a solution of two perfectly miscible liquids. Liquid A is the solvent, and liquid B is the solute. How can you change the solution so that liquid B becomes the solvent?

Answer 2

Add more of liquid B to the solution.

Question 3

How can the benzene in this mixture be classified in a solution where 23 g of benzene are dissolved in 82 g of carbon tetrachloride (CCl4 )?

Answer 3

as a solute

Question 4

You have 500 mL of a 5.0 M solution of nitric acid HNO3 (63.01 g / mol) dissolved in water. How many grams of nitrogen does the solution contain?

Answer 4

160 g

Question 5

Which of the following describes the best way to prepare 500. mL of a 0.20 M solution of benzene (C6H6 ) (78.11 g / mol) dissolved in carbon tetrachloride (CCl4 ) (153.82 g / mol)?

Answer 5

Add 7.8 g of C6H6 to a volumetric flask. Then fill the flask to the 500 mL line with CCl4.

Question 6

In a precipitation reaction, copper(II) sulfide (CuS) is produced as the precipitate, and ammonium and chloride ions are the spectator ions. What is the balanced total ionic equation for this reaction?

Answer 6

NH4+(aq) + S2-(aq) + Cu2+(aq) + 2Cl-(aq) -> CuS(s) + NH4+(aq) + 2Cl-(aq)

Question 7

Which of these compounds is an acid in aqueous solution?

Answer 7

H2SO4

Question 8

If 145.0 mL of 0.350 M lithium hydroxide is required to titrate 35.0 mL of an unknown monoprotic acid, what is the molar concentration of the unknown acid?

Answer 8

1.45 M

Question 9

In an oxidation-reduction reaction, it required 25.6 ml of a 0.65 M potassium permanganate solution to reach the equivalence point with 15.0 mL of an iron(II) sulfate solution. What is the molar concentration of the iron(II) sulfate solution? The net ionic equation for the reaction is:
MnO4-(aq) + 5Fe2+(aq) + 8H+(aq) -> Mn2+(aq) + 5Fe3+(aq) + 4H2O(l)

Answer 9

5.6 M

Question 10

A 15.00 mL sample of unknown concentration of sulfuric acid is precititated with excess lead(II) nitrate and a precipitate of lead(II) sulfate is collected. The dried sample of PbSO4 has a mass of 5.354 grams. What is the concentration of the unknown sulfuric acid solution?

Answer 10

1.175 M

Question 11

A sample of iron ore has a mass of 2.47 g. The sample is dissolved in an acidic solution, and the iron is titrated with 35.3 mL of a 0.120 M solution of K2Cr2O7. What is the percent by mass of iron in the ore? (Assume that all of the iron from the sample exists as Fe2+ in solution. The net ionic equation of the redox reaction is shown below.)
6Fe2+(aq) + Cr2O72-(aq) + 14H+(aq) -> 6Fe3+(aq) + 2Cr3+(aq) + 7H2O(l)

Answer 11

57.5%

Question 12

You have 47.2 mL of a solution of copper(II) chloride (CuCl2 ). You need to determine the concentration of Cu2+ in the solution gravimetrically. You add an excess of aqueous sodium sulfide and isolate 96.0 mg of CuS. What was the concentration of the original CuCl2 solution?

CuCl2 + S2− → CuS(s) + 2Cl −

Answer 12

2.13 × 10−2 M

Question 13

Iron is sometimes coated with a layer of zinc. The zinc protects the iron from rusting because it reacts with oxygen gas and hydrogen ions more readily than iron does. What can you conclude about zinc based on this information? (The first step in the reaction involving the rusting of iron is shown below.)

2Fe(s) + O2(g) + 4H+(aq) -> 2Fe2+(aq) + 2H2O(l)

Answer 13

Zinc is a stronger reducing agent than iron.

Question 14

What is the total number of electrons transferred in the following oxidation-reduction reaction?
2Al(s) + 3Cu2+ (aq) + 6Cl − (aq) →
2Al 3+ (aq) + 6Cl − (aq) + 3Cu (s)

Answer 14

6

Question 15

Which of these titrations will require the greatest volume of base to reach the last equivalence point?

Answer 15

50 mL of 0.01 M, phosphoric acid, H3PO4 titrated with 0.01 M KOH

Question 16

How many milliliters of a 0.208 M solution of NaOH will it take to titrate 7.34 mL of a 0.820 M solution of HBr?

Answer 16

28.9 mL

Question 17

Heptane (C7H16 ) is insoluble in water. Which choice best explains why water is incapable of dissolving heptane (C7H16 )?

Answer 17

Heptane is a nonpolar molecule composed of a long hydrocarbon chain.

Question 18

Solid iodine (I2 ) is nearly insoluble in water, somewhat soluble in ethanol, and very soluble in hexane. Based on this information, what can you conclude about I2?

Answer 18

It contains a nonpolar bond.

Question 19

Suppose a researcher spills a small amount of strong acid in a laboratory. The addition of which of these substances would make the spill safer to clean up?

Answer 19

an excess of weak base

Question 20

You have two colorless aqueous solutions, X and Y. You also have an indicator that turns purple in basic solutions, green in neutral solutions, and red in acidic solutions. Solution X turns purple when you add a small amount of the indicator to it. When you then add 5 mL of Solution Y to Solution X, the resulting mixture turns green. What can you conclude about Solution Y?

Answer 20

It is acidic.

Question 21

In what way is gravimetric analysis similar to an acid-base titration?

Answer 21

Both utilize the stoichiometry of a known reaction to establish the number of moles of the unknown.

Question 22

Which of the following compounds would you expect to be the most soluble?

Answer 22

sodium sulfate

Question 23

An ionic compound that contains lead is soluble in water. Of the four compounds listed, which should be the most soluble.

Answer 23

Pb(ClO3 )2

Question 24

MnO4− is deep purple in aqueous solution, while Mn2+ is colorless. Suppose a solution of KMnO4 is being used as a sample in a redox titration against iron(II) sulfate. What would be indicated by a sudden color change in the solution from purple to colorless?

Answer 24

The equivalence point of the redox reaction has been reached.

Question 25

Which of the following shows a correctly balanced reaction in which cerium is reduced?

Answer 25

Ce4+ (aq) + Fe2+ (aq) →

Ce3+ (aq) + Fe3+ (aq)