chapter 17 chem!!!

The reduction potential to the metal of Ba2+ is -1.57 V and that of Cu2+ is +0.34 V. The cell potential for the reaction Ba(s) + Cu2+(aq) ® Ba2+(aq) + Cu(s) is therefore: (+1.57) + (-0.34) (+1.57) + (+0.34) 2 ´ (-1.57) + 2 ´ (0.34) (-1.57) + (0.34)-1.57) + (0.34)

(+1.57) + (+0.34)

What is Eel for a voltaic cell using the two half-reactions at 25°C? -2.46 V -0.74 V +2.46 V +0.74 V

+2.46 V

The E° for Mg → Mg'* + 2 e is +2.37 volts. The E° for 2 Mg** + 4 e - 2 Mg is Do without a calculator. -2.37 volts 2.37 volts 4.74 volts -4.74 volts

-2.37 volts

A common car battery consists of six identical cells, each of which carries out the reaction: Pb + PbO2 + 2HSO4- + 2H+ ® 2PbSO4 + 2H2O The value of mc005-1.jpg for such a cell is 2.039 V. Calculate DG° at 25 °C for the reaction. -786.9 kJ -393.5 kJ -98.37 kJ -196.7 kJ

-393.5 kJ

Determine DG° for a cell that utilizes the following reaction: Cl2(g) + 2Br-(aq) ® 2Cl-(aq) + Br2(l) The standard reduction for the chlorine gas is 1.360 volts and the standard reduction for the bromine liquid is about 1.078 volts. -235 kJ -27.2 kJ -54.4 kJ -470 kJ

-54.4 kJ

When the reaction 2 Mg + Fe'+ - 2 Mg?* + Fe'* comes to equilibrium, the E°cel value (cell potential) becomes 0.00 V 3.14 V 0.83 V 1.60 V

0.00 V

For a certain reaction, AH° = -74.4 kJ and 45° = -227 J/K. If n = 3, calculate e° for the reaction at 25°C. 0.277 V 0.0700 V 0.0233 V 0.491 V

0.0233 V

What is the value of k for a first-order reaction with a half-life of 23.1 s? Do this without a calculator. 0.0300 s-1 0.0300 s 16.0 s-1 16.0 s

0.0300 s-1

An initial mixture of 5.00 M N2 and 5.00 M H2 is placed in a reaction vessel and allowed to come to equilibrium. The equilibrium concentration of the NH3 is deteremined to be 2.00 M. Determine K for the reaction below. (Do without a calculator) mc007-1.jpg 0.250 1.00 0.125 0.500

0.125

The standard free energies of formation of several species are: What is the standard reduction potential of methanoic acid in aqueous solution (i.e., for HCOOH + 4H+ + 4e- ® CH3OH + H2O)? -0.126 V 0.506 V -0.718 V 0.126 V

0.126 V

If 200. mL. of 0.60 M MgClaq) is added to 400. mL of dis- tilled water, what is the concentration of Mg'+(aq) and Cl (aq) in the resulting solution? (Assume volumes are additive.) 0.20 M Mg ion & 0.20 M Cl ion 0.40 M Mg ion & 0.40 M Cl ion 2.0 M Mg ion & 2.5 M Cl ion 0.20 M Mg ion & 0.40 M Cl ion

0.20 M Mg ion & 0.40 M Cl ion

Gold is produced electrochemically from an aqueous solution of Au(CN)2- containing an excess of CN-. Gold metal and oxygen gas are produced at the electrodes. How many moles of O2 will be produced during the production of 1.00 mole of gold? 1.00 0.25 0.50 3.56

0.25

A cell is set up with copper and lead electrodes in contact with CuSO4(aq) and Pb(NO3)2(aq), respectively, at 25°C. The standard reduction potentials are: Pb2+ + 2e- ® Pb e° = -0.13 V Cu2+ + 2e- ® Cu e° = +0.34 V If the Pb2+ and Cu2+ are each 1.0 M, the potential of the cell, in volts, is: 0.92 V 0.58 V 0.22 V 0.47 V

0.47 V

Balance the following redox equation in basic solution. What is the coefficient of the water? NO2-(aq) + Al(s) ® NH3(g) + AlO2-(aq) 4 6 1 2

1

How many moles of solid chromium can be deposited from a CrCl solution when a steel wrench is electroplated with a current of 3.0 amps for 965 seconds? Do this without a calculator. 1.0 ' 10-2 3.0 ' 10-2 3.3 ' 10-3 5.0 ' 10-3

1.0 ' 10-2

The reduction potentials for Ni2+ and Sn2+ are as follows: Ni2+ + 2e- ® Ni, e° = -0.231 V Sn2+ + 2e- ® Sn, e° = -0.140 V Calculate the equilibrium constant at 25 °C for the reaction: Sn2+ + Nimc006-1.jpgSn + Ni2+

1.2 '10 3

If an electrolysis plant operates its electrolytic cells at a total current of 1.8 ´ 106 amp, how long will it take to produce one metric ton (one million grams) of Mg(s) from seawater containing Mg2+? (1 faraday = 96,485 coulombs) 1.2 days 0.61 h 1.2 h 37 min

1.2 h

An antique automobile bumper is to be chrome plated. The bumper, which is dipped into an acidic C5203 7 solution, serves as a cathode of an electrolytic cell. The atomic mass of Cr is 51.996; 1 faraday = 96,485 coulombs. If the current is 10.0 amperes, how long will it take to deposit 105 grams of Cr(s) onto the bumper? 5.41 h 2.02 min| 1.35 days 54.1 min

1.35 days

What is the value of Q, the reaction quotient, for this cell reaction? 6.7 x 1040 1.5 x 10'41 6.7 × 103 1.5 × 10-4

1.5 x 10'41

Using the following data to calculate Ksp for PbSO4. Pb02 + 4H++ SO,2+ +1.69 2e* → PbSO(s) + 2H20 PbO2 + 4H* + 2e → Pb2++ +1.46 2H20 2.5 × 10-107 5.9 x 107 1.7 × 10-8 4.0 × 10106

1.7 × 10-8

How many electrons are transferred in the following reaction? 2ClO3- + 12H+ + 10I- → 5I2 + Cl2 + 6H2O 5 12 10 2

10

Copper may be used for electroplating, with a half-reaction of Cu? + 2 € - Cu. If a current of 10.0 A is applied to a Cu'* solution for 60.0 minutes, the mass of copper plated out can be calculated as (Do without a calculator) 96,500 x (1/10.0) × (1/2.00) x (1/3600.) x (63.5) 10.0 × 3600. × (1/96,500) × (1/2.00) x 63.5 10.00 × 3600. x (6.022 ' 1023) × (1/2.00) x 63.5 96,500 × (1/10.0) x (1/2.00) x (1/3600.) x (1/63.5)

10.0 × 3600. × (1/96,500) × (1/2.00) x 63.5

Alcohols are organic compounds containing a hydroxyl (-OH) group. WHen a solution containing dichromate ions is added to most alcohols, chromium(III) iions are formed. The color of the sooution changes from bright orange to green. mc001-1.jpg What is the coefficient for water in the balanced redox reaction? 11 19 6 14

11

How many peaks would be displayed in an X-ray PES emission spectrum of mercury (Z=80)? 11 12 14 13

14

Nickel is electroplated from a NiSO4 solution. A constant current of 5.50 amp is applied by an external power supply. How long will it take to deposit 100. g of Ni? The atomic mass of Ni is 58.69. 16.6 h 18.2 min 55.4 s 8.30 h

16.6 h

Balance the following oxidation-reduction reaction using the half-reaction method. Cr2077 + 12@ Cr3+ +103 In the balanced equation, the coefficient of water is: 11 17 7 4

17

Balance the following redox equation in basic solution. What is the coefficient of the water? MnO, (aq) + HCOOH(aq) ® Mn?+(aq) + CO2(g) 8 4 2 6

2

Determine the equilibrium constant at 25°C.

2.266 × 10 8

A common car battery consists of six identical cells each of which carries out the reaction: Pb + PbO2 + 2HSO4- + 2H+ ® 2PbSO4 + 2H2O Suppose that in starting a car on a cold morning a current of 125 amperes is drawn for 18.4 seconds from a cell of the type described above. How many grams of Pb would be consumed? (The atomic weight of Pb is 207.19.)

2.47 g

What is ΔG° for the following electrochemical equation? (e°red(Ag+/Ag) = 0.800 V, e°red(Cd2+/Cd) = -0.403 V) 2Ag(s) + Cd2+(aq) → 2Ag+(aq) + Cd(s) -232 kJ/mol 464 kJ/mol 232 kJ/mol 116 kJ/mol

232 kJ/mol

Ammonium metavandate reacts with sulfur dioxide in acidic solution as follows (hydrogen ions and H2O omitted): xVO3- + ySO2 ® xVO2+ + ySO42- The ratio x : y is 1 : 3 1 : 2 1 : 1 2 : 1

2:1

What is the cell reaction for the voltaic cell Cr(s) | Cr3+(aq) || Cl-(aq) | Cl2(g) | Pt? 2Cr3+(aq) + 6Cl-(aq)mc025-2.jpg2Cr(s) + 3Cl2(g) Cr(s) + 2Cl-(aq)mc025-1.jpgCl2(g) + Cr3+(aq) 2Cr(s) + 3Cl2(g)mc025-4.jpg2Cr3+(aq) + 6Cl-(aq) Cr(s) + 3Cl2(g)mc025-3.jpgCr3+(s) + 2Cl-(aq)

2Cr(s) + 3Cl2(g)mc025-4.jpg2Cr3+(aq) + 6Cl-(aq)

What is the balanced chemical equation corresponding to the following cell diagram? Na(s) | Na+(aq) || Cu2+(aq) | Cu(s) 2Na(s) + Cu(s) ® 2Na+(aq) + Cu2+(aq) 2Na(s) + Cu2+(aq) ® 2Na+(aq) + Cu(s) 2Na(s) + 2Na+(aq) ® Cu2+(aq) + Cu(s) Cu(s) + 2Na+(aq) ® 2Na(s) + Cu2+(aq)

2Na(s) + Cu2+(aq) ® 2Na+(aq) + Cu(s)

The following reaction occurs in aqueous acid solution: NO3- + I- ® IO3- + NO2 In the balanced equation the coefficient of water is: 2 4 1 3

3

How many electrons are transferred in the balanced reaction? 30 22 5 6

30

Methanol (CHOH) can react with oxygen gas to produce form- aldehyde (H,CO) and water. How much formaldehyde can be produced by reacting 4.0 moles of methanol with 4.0 moles of oxygen gas 6.0 moles 4.0 moles 2.0 moles 8.0 moles

4.0 moles

Balance the following redox equation in basic solution. What is the coefficient of the hydroxide ion? MnO4-(aq) + HCOOH(aq) ® Mn2+(aq) + CO2(g) 8 2 4 6

6

Balance the following redox equation in acidic solution. What is the coefficient of the water? CH3OH(aq) + Cr2O72-(aq) → CH2O(aq) + Cr3+(aq) 6 2 14 7

7

Balance the following redox equation in acidic solution. What is the coefficient of the H+ ion? CH3OH(aq) + Cr2O72-(aq)→ CH2O(aq) + Cr3+(aq) 8 3 4 2

8

Calculate the solubility product of silver iodide at 25°C given the following data: e°(V) -0.15 Agl(s) + e® Ag(s) + 1' 12(5) + 2e ® 21* +0.54 Agt + e'® Ag(s) +0.80 8.4* 10-17 2.1 ' 10-12 2.9 ' 10-3 1.9 ' 10-4

8.4* 10-17

Which of these changes would increase the value of mc006-2.jpg? Increase the temperature of each solution by 20°C Add 1.5 g of AgNO3 to the left beaker. Add 0.10 mole of NaCl(s) to the left beaker, producing a precipitate. Add 50.0 mL of water to each beaker.

Add 1.5 g of AgNO3 to the left beaker.

You wish to plate out zinc metal from a zinc nitrate solution. Which metal, Al or Ni, could you place in the solution to accomplish this? Both Al and Ni would work. Neither Al nor Ni would work. Ni Al

Al

Which best explains why an aluminum can may be crushed without it breaking into pieces? mc010-1.jpg Aluminum has delocalized valence electrons with nondirectional bonding. Aluminum has ionic bonds that are not easily broken. Aluminum has localized valence electrons with directional bonding. Aluminum has covalent bonds that are not easily broken.

Aluminum has delocalized valence electrons with nondirectional bonding.

Which element is oxidized in the reaction? Cr H C O

C

Each of the following salts has a solubility of 1.0 ´ 10-5 M. Rank the salts in order of lowest to highest Ksp. AX, B2X, C2X3, D3X D3X < C2X3 < B2X < AX D3X < B2X < AX < C2X3 C2X3 < D3X < B2X < AX C2X3 < D3X < AX < B2X

C2X3 < D3X < B2X < AX

Which of the following correctly describes the ease of oxidation of the substances listed under standard state conditions? Pb?* > Sn'* > Co" > Zn'+ > Ca?+ Pb > Sn > Co > Zn > Ca Ca > Zn > Co > Sn > Pb Ca"* > Zn** > Co'* > Sn"> Pb2*

Ca > Zn > Co > Sn > Pb

(Acetone is slightly polar, ethylene glycol is polar, benzene is non-polar) Compound 1 = benzene, compound 2 = ethylene glycol, compound 3 = acetone Compound 1 = ethylene glycol, compound 2 = acetone, compound 3 = benzene Compound 1 = benzene, compound 2 = acetone, compound 3 = ethylene glycol Compound 1 = acetone, compound 2 = benzene, compound 3 = ethylene glycol

Compound 1 = ethylene glycol, compound 2 = acetone, compound 3 = benzene

When current is allowed to flow, which species is oxidized? Cr2O72- Mn2+ MnO4- Cr3+

Cr3+

When electricity is passed through molten sodium chloride, solid sodium metal is formed at the cathode and chlorine gas is formed as the anode. Which of the following is true regarding this reaction? DG is positive. The equilibrium constant has a value greater than 1. Electrons travel from the cathode to the anode. The reaction is at equilibrium.

DG is positive

MnO,- + 5 Fe?+ + 8 H* → Mn** + 5 Fe3+ + 4 H20, Fe2+ is oxidized and MnO41- is reduced. Fe3+ is oxidized and Mn2+ is reduced. electrons are transferred from Mn2+ to Fe2+ . H1+ is oxidized and MnO41- is reduced.

Fe2+ is oxidized and MnO41- is reduced.

In which of the following groups are the noble gases arranged correctly in order of increasing boiling point? Kr, Xe, Ne, He He, Ne, Kr, Xe Xe, Kr, Ne, He Ne, He, Kr. Xe

He, Ne, Kr, Xe

According to the graph below, what chemical was added to the equilibrium mixture and how did the system respond? mc011-1.jpg Hydrogen was added and the concentration of nitrogen decreased. Hydrogen was added and the concentration of ammonia decreased. Ammonia was added and the concentration of hydrogen increased. Ammonia was added and the concentration of ammonia increased.

Hydrogen was added and the concentration of nitrogen decreased.

Which of the following is true for a solid with a structure as shown in the diagram below? It is an ionic solid and consists of ions held together by electrostatic attractions. It is a molecular solid and consists of nonpolar molecules with intermolecular forces. It is a molecular solid and consists of polar molecules with dipole-dipole attractions. It is an atomic solid and consists of atoms with electrostatic attractions

It is a molecular solid and consists of polar molecules with dipole-dipole attractions.

You make a cell with an aluminum electrode in a solution of aluminum nitrate and a zinc electrode in a solution of zinc nitrate. A|3+ + 3e? → Al(s) E = -1.66 v Zn?+ + 2el → Zn(s) E = -0.76 v If you could increase the concentration of A|3+ *, which of the following is true about the cell potential? Cannot be determined. It would increase. It would remain constant. It would decrease.

It would decrease.

A student dissolved 30 g of an unknown compound in 50 g of water at 39°C. What is the unknown compound? mc009-1.jpg KCl NH4Cl KNO3 Ce2(SO4)3

KNO3

Which of the following is true regarding the salt bridge in this voltaic cell? Electrons travel through the salt bridge from the anode to the cathode. Potasssium ions travel to the cathode, and nitrate ions travel to the anode. Electrons travel through the salt bridge from the cathode to the anode. Potassium ions travel to the anode, and nitrate ions travel tothe cathod

Potasssium ions travel to the cathode, and nitrate ions travel to the anode.

Which of the following cell diagrams represents a galvanic cell? (e°red(Sn2+/Sn) = -0.138V, e°red(H+/H2) = 0.00 V) Sn(s), H2(g) | H+(aq) || Sn2+(aq) | Pt(s) Pt(s) | Sn2+(aq) || H+(aq) | H2(g), Sn(s) Sn(s) | Sn2+(aq) || H+(aq) | H2(g), Pt(s) Pt(s), H2(g) | H+(aq) || Sn2+(aq) | Sn(s)

Sn(s) | Sn2+(aq) || H+(aq) | H2(g), Pt(s)

An example of an alloy is shown in the diagram below. Compared with the pure metal X, how would you expect the properties of the alloy to vary? mc009-1.jpg The alloy has lower malleability and higher density. The alloy has lower malleability and lower density. The alloy has higher malleability and higher density. The alloy has higher malleability and lower density.

The alloy has lower malleability and higher density.

Consider the following data for the dissolution of an alcohol, R-OH, in a solvent, X-OH. DH1 = 65 kJ/mol, DH2 = 340 kJ/mol, DH3 = -8 kJ/mol. Predict and explain the solubility of this compound. Do this without a calculator. The compound would not be soluble because DS is unknown. The compound would be soluble because the solute and solvent both have -OH in their formulas. The compound would not be soluble because DHsoln = 397 kJ/mol, which is very endothermic. The compound would not be soluble because DH3 = negative and exothermic.

The compound would not be soluble because DHsoln = 397 kJ/mol, which is very endothermic.

Which of the following is true for the cell shown here? Zn(s) | Zn2+(aq) || Cr3+(aq) | Cr(s) The zinc is reduced. The electrons flow from the chromium to the zinc. The chromium is oxidized. The electrons flow from the zinc to the chromium.

The electrons flow from the zinc to the chromium.

Considering the photoelectron specturm of carbon, which of the following best explains the large difference in binding energy between the peaks on the leaft and on the right? mc005-1.jpg The electrons generating the peak on the right have greater electron shielding. You Answered The electrons generating the peak on the right are further away from the nucleus. There are four electrons all together in the group on the left. Correct Answer The electrons generating the peak on the left are further from the nucleus and experience greater electron shielding.

The electrons generating the peak on the left are further from the nucleus and experience greater electron shielding.

Consider the dissolution of an ionic salt in water. Which of the following statements best explains why this process is considered a physical change? Dissolution of an ionic salt is mostly a physical change, and all physical changes are reversible. The ionic salt can be recovered by solidification of the water. Dissolution of an ionic salt is mostly a chemical change, and all chemical changes are reversible. The ionic salt can be recovered by evaporation of the water.

The ionic salt can be recovered by evaporation of the water.

The rate law of a reaction is determined to be rate = k[A][B]2 . Which statement would most likely describe this reaction? The reaction involves a one-step, termolecular mechanism. The reaction involves the formation of intermediates. The stoichiometry of the overall reaction must be A + 2B ® products. The reaction is catalyzed by an enzyme.

The reaction involves the formation of intermediates.

In the kinetic study, the natural logarithms of the absorbance values were plotted versus time, resulting in a straight line. What does this indicate about the order of the reaction with respect to the dichromate ion? The reaction is first order in dichromate. The reaction is zero order in dichromate. The order cannot be determined from this graph. The reaction is sceond order in dichromate.

The reaction is first order in dichromate.

The equilibrium constant is approximately 5 at room temperature, but the rate of reaction without a catalyst is very slow. How do the rates of the forward and reverse reactions compare at equilibirum? Done Exit The forward rate is 5 times faster than the reverse rate. There is not enough information to compare the rates. The reverse rate is 5 times faster than the forward rate. The reverse rate is the same as the forward rate.

The reverse rate is the same as the forward rate.

Which of the following describes what happens to the solubility of a slightly soluble ionic compound when a common ion is added to the solution? The ionic compound dissolves more rapidly. The solubility of the ionic compound is reduced. The solubility of the ionic compound is increased. There is no effect on the solubility of the ionic compound.

The solubility of the ionic compound is reduced.

Of Sn2*, Ag*, and/or Zn2+, *, which could be reduced by Cu? Sn?+ Zn2+. Ag* Two of them could be reduced by Cu.

Two of them could be reduced by Cu.

Solve without using a calculator. The simplest formula for a compound made from element X (molar mass = 79.0 g/mol) that is 21.0% nitrogen by mass is X3N2 XN2 X2N3 XN

X2N3

Which of the following reactions is possible at the anode of a galvanic cell? Zn2+ + Cu→ Zn + Cu2+ Zn→ Zn2+ + 2e- Zn + Cu2+ → Zn2+ + Cu Zn2+ + 2e-→ Zn

Zn→ Zn2+ + 2e-

For a particular reaction in a galvanic (voltaic) cell DS° is negative. Which of the following statements is true? e will decrease with an increase in temperature. DG° > 0 for all temperatures. e will not change when the temperature increases. e will increase with an increase in temperature.

e will decrease with an increase in temperature.

For a reaction in a voltaic cell bothΔH° and ΔS° are positive. Which of the following statements is true? ΔG° > 0 for all temperatures. e°cell will decrease with an increase in temperature. e°cell will not change when the temperature increases. e°cell will increase with an increase in temperature.

e°cell will increase with an increase in temperature.

The galvanic cell based on the reactions Ag' +1 e - Ag (E° = +0.80 V) and Fe' + 1 er → Fe"* (E° = +0.77 V) has an overall cell potential difference (voltage) of +1.57 V. has the mass of the silver electrode decreasing as this reaction proceeds. has electrons flowing from Fe2* to Ag'*. has electrons lost by Ag'* and gained by Fe?+.

has electrons flowing from Fe2* to Ag'*.

Which of the following is endothermic? Water freezes to form ice. Steam condenses on a bathroom mirror. Coffee cools as it sits. Ice cream melts.

ice cream melts

If the tin electrode was replaced with a strip of zinc, how would the cell voltage change? You Answered become zero no change decrease increase

increase

You make a cell with an aluminum electrode in a solution of aluminum nitrate and a zinc electrode in a solution of zinc nitrate. You make a cell with an aluminum electrode in a solution of aluminum nitrate and a zinc electrode in a solution of zinc nitrate. If you could increase the concentration of Zn2+, which of the following is true about the cell potential? It would decrease. It would increase. Cannot be determined. It would remain constant.

it would increase

For the reaction A = B, for which value of K is the concentration of the reactants greater than the concentration of the products? K is less than 1 K equals 1 K equals 0 K is greater than 1

k is less than 1

What would happen to the cell emf if NH were added to the silver cell and Ag(NH3)2"* forms? cannot be determined without additional information. reduced no change increased

reduced

The function of a salt bridge (or porous barrier) in an electrochemical cell (galvanic cell) is to allow ions to flow from the oxidizing side of the cell to the reducing side. to keep the net charge on each side at zero. to encourage charge building up on both sides of the cell. through the wire from reducting agent to oxidizing agent.

to keep the net charge on each side at zero.