Questions 25 and 26 refer to the following PESimages.pcmac.org/.../Thanksgiving_Take_home_test.docx · Web viewElectrode A is the cathode and it gains mass since metal ions are being

1. CaCO3 (s) + 2H+ (aq) Ca2+ (aq) + H2O (l) + CO2 (g) If the reaction above took place at standard temperature and pressure and 150 grams of CaCO3 (s) were consumed, what was the volume of CO2 (g) produced at STP?

A) 11 L B) 22 LC) 34 L D) 45 L

2. Analyze the Mass Spectrum Graph. Calculate the average atomic mass of the unknown element.

A) 6.0 amu B) 5.2 amuC) 5.0 amu D) 4.2 amu

3. If solutions containing equalmolar amounts of AgNO3 and KCl are mixed, what is the identity of the spectator ions?a. Ag+, NO3

-, K+, and Cl- c. K+ and Ag+

b. Ag+ and Cl- d. K+ and NO3-

4. Choose the correct net ionic equation representing the reaction that occurs when solutions of Na2CO3 and HCl are mixed a. CO3

-2 + H+ H2O + CO2

b. 2Na+ + CO3-2 + 2H+ + 2Cl- 2Na+ + 2 Cl- + H2CO3

c. Na+ + Cl- NaCld. CO3

-2 + 2H+ H2O + CO2

5. How many moles of Na2SO4 must be added to 500 mL of water to create a solution that has a 2 M concentration of the Na+ ion?a. 0.5 moles c. 2 molesb. 1 mole d. 4 moles

6. Which of the following would be considered a weak electrolyte?a. HCl c. Mg(OH)2

b. NaCl d. LiNO3

7. What is the volume of 0.05 M HCL that is requird to neuralize 50 mL of 0.10 M Sr(OH)3?a. 100 mL c. 300 mLb. 200 mL d. 400 mL

8. If solutions of Iron III nitrate and sodium carbonate are mixed, what would be the formula of the precipitate?a. Fe3CO3 c. NaNO3

b. Fe2(CO3)3 d. no precipitate will form9. A redox reaction has an equilibrium constant of K = 2.6 x 105. Which of the following statements best represents the

algebraic signs of Ecello and ∆Grxn

o for this reaction?

A. Ecello is positive and ∆Grxn

o is positive.

B. Ecello is negative and ∆Grxn

o is negative.

C. Ecello is positive and ∆Grxn

o is negative.

D. Ecello is negative and ∆Grxn

o is positive.

10. Which of the following expressions is correct for the maximum mass of copper, in grams, that cou1d be plated out by electrolyzing aqueous CuCl2 for 16 hours at a constant current of 3.0 amperes? (1 faraday = 96,500 coulombs)

A.(16 ) (3600 )(3.0)(63.55 )(2)

96500

B.(16 ) (3600 )(3.0)(63.55 )

(96500)(2)

C.(16 ) (3600 )(3.0)(63.55 )

96500

D.(16 ) (60 ) (3.0 ) (96500 )(2)

63.55Questions 11-13 refer to the following electrochemical cell.

11. Which of the following statements applies to the change in mass of the electrodes involved in this electrochemical cell?

A. Electrode A is the anode and it gains mass since metal ions are being converted to metal atoms which often adhere to the electrode.

B. Electrode B is the anode and it gains mass since metal ions are being converted to metal atoms which often adhere to the electrode.

C. Electrode A is the cathode and it gains mass since metal ions are being converted to metal atoms which often adhere to the electrode.

D. Electrode B is the cathode and it gains mass since metal ions are being converted to metal atoms which often adhere to the electrode.

12. Which of the following best describes this electrochemical cell?

A. Electrode A is the anode since anions are present in its half-cell and the current flows from cathode to anode.B. Electrode C is the cathode since cations are present in its half-cell and the current flows from anode to cathode.C. Electrode A is the anode and Electrode C is the cathode since the current always flows from cathode to anode.D. Electrode C is the anode and Electrode A is the cathode since the current always flows from anode to cathode.

13. Which of the following best describes the function of the portion of the electrochemical cell labeled B?

A. Structure B functions to complete the electrical circuit present in the electrolytic cell.B. Structure B provides soluble anions that migrate to the anode as well as soluble cations that migrate to the cathode,

thus maintaining a balance of charge in the electrolytic cell.C. Structure B provides soluble anions that migrate to the anode as well as soluble cations that migrate to the cathode,

thus maintaining a balance of charge in the galvanic cell.D. Structure B provides soluble anions that migrate to the cathode as well as soluble cations that migrate to the anode,

thus maintaining a charge balance in the galvanic cell.

Questions 14-16 refer to the following experimental apparatus.

An experiment was conducted in which two test tubes were filled with water at 25oC and 1 atm pressure. Each test tube was subsequently inverted into a beaker containing water which was then acidified.

14. Which of the following best describes the reaction taking place in Test Tube A?

A. Ecello is positive and ∆Grxn

o is positive.

B. Ecello is negative and ∆Grxn

o is negative.

C. Ecello is positive and ∆Grxn

o is negative.

D. Ecello is negative and ∆Grxn

o is positive.

15. Which of the following best represents the half-reaction occurring at the anode?A. H2O(l) → H2(g) + O2(g)B. 2 H2O(l) → 2 H2(g) + O2(g)C. 2 H2O(l) → O2(g) + 4 H+(aq) + 4 e–

D. 2 H2O(l) + 2 e– → H2(g) + 2 OH–(aq)16. Which of the following best explains the difference in the water levels inside the two test tubes?A. As the reaction proceeds, water is being dissociated at a slower rate in Test Tube A than in Test Tube B.B. As the reaction proceeds, water is being dissociated at a faster rate in Test Tube A than in Test Tube B.C. As the reaction proceeds more water is being dissociated in Test Tube A than in Test Tube B.D. As the reaction proceeds, water is being dissociated at the same rate in each test tube, but twice as much gas is

being formed in Test Tube A.

17. In the electroplating of nickel, 0.200 faraday of electrical charge is passed through a solution of NiSO4. What mass of nickel is deposited?

A. 2.94gB. 5.87 g

C. 11.7 gD. 58.7 g

Questions 18 and 19 refer to the relationships among the three quantities illustrated below.

18. Which of the following mathematical relationships is represented by letter B in the diagram above?

A. ∆G = - nFECello

B. ∆G = -RTlnK

C. ECello =0.0592

nlog Q

D. ECello =Ered

o +Eoxo

19. Which of the following mathematical relationships is represented by letter A in the diagram above?

A. ∆G = - nFECello

B. ∆G = -RTlnK

C. ECello =0.0592

nlog Q

D. ECello =Ered

o +Eoxo

20. Cu(s) + 2 Ag+ → Cu2+ + 2 Ag(s)If the equilibrium constant for the reaction above is 3.7 x1015, which of the following correctly describes the standard voltage, E°, and the standard free energy change, ∆G°, for this reaction?

A. E° is positive and ∆G° is negative.B. E° is negative and ∆G° is positive.

C. E° and ∆G° are both positive.D. E° and ∆G° are both zero.

Questions 21 and 22 refer to the electrochemical cell pictured below.

21. Consider the electrochemical cell pictured above. The thermodynamically favorable reaction that occurs when the cell above operates is:

2 Ag+ + Cd(s) → 2 Ag(s) + Cd2+

Which of the following occurs once current is allowed to flow for five minutes?

A. Voltage increases.B. Voltage decreases.

C. Voltage becomes zero and remains at zero.D. No change in voltage occurs.

22. Which of the following occurs if a 50-milliliter sample of a 2-molar Cd(NO3)2 solution is added to the left beaker?

A. Voltage increases.B. Voltage decreases.

C. Voltage becomes zero and remains at zero.D. No change in voltage occurs.

23. Zn(s) + Cu2+ → Zn2+ + Cu(s)

An electrolytic cell based on the reaction represented above was constructed from zinc and copper half-cells. The observed voltage was found to be 1.00 volt instead of the standard cell potential, E°, of 1.10 volts. Which of the following could correctly account for this observation?

A. The copper electrode was larger than the zinc electrode.B. The Zn2+ electrolyte was Zn(NO3)2, while the Cu2+ electrolyte was CuSO4.C. The Zn2+ solution was more concentrated than the Cu2+ solution.D. The solutions in the half-cells had different volumes.

24. Calculate H for the reaction below using the following data.

N2 (g) + O2 (g) 2 NO (g) H = +180.5 kJ

N2 (g) + 3 H2 (g) 2 NH3 (g) H = -91.8 kJ

2 H2 (g) + O2 (g) 2 H 2O (g) H = -483.6 kJ

4 NH3 (g) + 5 O2 (g) 4 NO (g) + 6 H2O (g)

Questions 25 and 26 refer to the following PES data.

25. How many valence electrons are present in this element?

A) 2B) 6C) 8D) 10

26. What is the identity of this element?

E) OF) FG) NeH) Na

Questions 27 and 28 refer to the ionization energies for element X listed in the table below.

Ionization Energies for element X (kJ mol-1)

First Second Third Fourth Five

580 1,815 2,740 11,600 14,800

27. On the basis of the data, element X is most likely to beA) NaB) Mg

C) AlD) Si

28. How many valence electrons are present in this atom?A) 1B) 2

C) 3D) 4

Questions 29 and 30 refer to the following PES data.

29. The PES data above shows all of the electrons present in the atom. Which specific electrons are associated with the

peak at 0.59 MJ/mol?

a. 2pb. 3sc. 3pd. 4s

30. What is the significance of the relative height of the peaks at 34.0 MJ/mol and 42.7 MJ/mol?

a. The height of the peaks represent the amount of energy associated with removing an electron from a specific energy level.

b. The height peaks represent the amount of energy associated with removing an electron from a specific energy sublevel.

c. The height peaks represent the amount of distance a given electron is from the nucleus.d. The height peaks represent the relative number of electrons in each sublevel.

31.

Which of the following best describes why the first ionization energy for an oxygen atom is lower than the first ionization energy for a nitrogen atom?

e. Less energy is required to remove an electron from an oxygen atom since the ionization energy increases across a period from left to right.

f. More energy is required to remove an electron from an oxygen atom since the ionization energy increases across a period from left to right.

g. Less energy is required to remove an electron from an oxygen atom due to the fact that the oxygen atom has two doubly-occupied 2p orbitals and nitrogen has only one.

h. Less energy is required to remove an electron from an oxygen atom due to the fact that oxygen has one doubly-occupied 2p orbital and nitrogen does not

32. The photoelectron spectra above show the energy required to remove a 1s electron from a nitrogen atom and from an oxygen atom. Which of the following statements best accounts for the peak in the upper spectrum being to the right of the peak in the lower spectrum?

A) Nitrogen atoms have a half-filled p subshell.B) There are more electron-electron repulsions in oxygen atoms than in nitrogen atoms.C) Electrons in the p subshell of oxygen atoms provide more shielding than electrons in the p subshell of nitrogen

atoms.D) Nitrogen atoms have a smaller nuclear charge than oxygen atoms.

4NH3 (g) + 5 O2 (g) 4 NO (g) + 6 H2O (g)

33. Calculate the H of the following reaction using heats of formations

___C3H8 (l) + ___O2(g) →___CO2 (g) + ___H2O (g) ΔH = __________

C3H8 (l) = - 103 .8 kJ/mol O2 (g) = 0 kJ/molCO2 (g) = -393.5 kJ/mol H2O (g) = - 242.0 kJ/mol

34. The value of ΔH° for the reaction below is -72 kJ/ mol. __________ kJ of heat are released when 4.0 mol of HBr is formed in this reaction.

A) -72B) 72 C) 0.44

D) 36 E) -144

35. The reaction for the combustion of butane is …___C2H6(g) +___ O2(g) ___CO2(g) + ___H2O(g) ΔHrxn = -4345kJ/ mol

a. Is this reaction endothermic or exothermic?b. Calculate the number of grams of butane needed to produce 134.0 kJ/mol of energy.

36. Of the following, is not zero for __________.

A) O2 (g)B) C (graphite) C) Hg (s)

D) F2 (g)E) Cl2 (g)

37. A chemical reaction that absorbs heat from the surroundings is said to be __________ and has a __________ ΔH at constant pressure.

A) exothermic, positiveB) endothermic, negative C) exothermic, negative

D) endothermic, positiveE) exothermic, neutral

38. Which statement is true? A) The reaction vessel cools when an exothermic reaction

occurs.B) An exothermic reaction transfers heat to the surroundings. C) Heat is evolved when an endothermic reaction occurs.

D) An endothermic reaction is characterized by a negative value of ΔH.

E) None of the above

39. In the reaction below, is zero for __________.

A) B) CO (g)

C)

D) Ni (s)

E) both CO (g) and

40. C2H4(g) + 3 O2(g) 2 CO2(g) + 2 H2O(g)For the reaction of ethylene represented above, ΔH is –1,323 kJ mol–1. What is the value of ΔH if the combustion produced liquid water H2O(l), rather than water vapor H2O(g)? (ΔH for the phase change 2H2O(g) 2H2O(l) is –88 kJ mol–1.)

A) –1,235 kJ/molB) –1,279 kJ/molC) –1,323 kJ/mol

D) –1,367 kJ/molE) –1,411 kJ/mol

41.V W X

Y Z

A section of the periodic table with all identification features removed is shown above. Which element has the smallest atomic radius?

A) WB) XC) YD) Z

42. N2(g) + 3 H2(g) 2 NH3(g)The reaction indicated above is thermodynamically spontaneous at 298 K, but becomes nonspontaneous at higher temperatures. Which of the following is true at 298 K?

A) ΔG, ΔH, and ΔS are all positive.B) ΔG, ΔH, and ΔS are all negative.C) ΔG and ΔH are negative, but ΔS is positive.

D) ΔG and ΔS are negative, but ΔH is positive.E) ΔG and ΔH are positive, but ΔS is negative.

43.

Cu(s) + 2 Ag+ → Cu2+ + 2 Ag(s)

If the equilibrium constant for the reaction above is 3.7 × 1015, which of the following correctly describes the standard voltage, E°, and the standard free energy change, ΔG°, for this reaction?

A) E° is positive and ΔG° is negative.B) E° is negative and ΔG° is positive.

C) E° and ΔG° are both positive.D) E° and ΔG° are both negative.

44. Which of the following must be true for a reaction that proceeds spontaneously from initial standard state conditions?.

A) ∆G° > 0 and Keq > 1B) ∆G° > 0 and Keq < 1

C) ∆G° < 0 and Keq > 1D) ∆G° > 0 and Keq > 1

45. I2(g) + 3 Cl2(g) → 2 ICl3(g)

According to the data in the table below, what is the value of ΔH° for the reaction represented above?

Bond Average Bond Energy (kJ/mol)

I⎯I 150Cl⎯Cl 240I⎯Cl 210

A) –870 kJ/molB) –390 kJ/mol

C) + 180 kJ/molD) + 450 kJ/mol

46. Which of the following best describes the energy in a chemical or physical change that is available to do useful work?

A) Free energyB) Ionization energy

C) Kinetic energyD) Lattice energy

Questions 47 and 48 refer to Maxwell- Boltsman molecular speed distribution shown on the graph below.

47. Assume the gas sample analyzed contains four noble gases at a temperature of 298.15 K (25 °C) and 1 atm pressue. Which of the following noble gases contained in the sample corresponds to the data graphed for gas D?

A) HeB) Ne

C) ArD) Xe

48. Assume the data graphed was collected at a constant pressure of 0.97 atm and represents four different temperature samples of pure neon gas. Which of the following temperatures most likely corresponds to the data graphed for sample “D”?

A) 273 KB) 298 K

C) 305 KD) 338 K

Speed (m/s)

Num

ber o

f Mol

ecul

es