Chemistry 1411
EXAM # 2
Activity Series of Metals in Aqueous Solution
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CHEM 1411 Exam # 2A
Name:________________________________
(Chapters 4,5,6, and 7)
Score:
Part I- ( 3 points each) - Please write your correct answer next to each question number, DO NOT CIRCLE.
____ 1. He diffuses 3.16 times as fast as another NOBLE gas (rHe/rX = 3.16). Identify the
gas.
A)Ar
B) Cl2
C) Kr
D)CO2
E) Ne
D) 1.25 L
E) 7.20 L
____ 2. 3. Which of the following is not a redox reaction?
A) HCl(aq) + Na(s) NaCl(aq) + H2 (g)
B) CuSO4(aq) + Zn(s)  ZnSO4(aq) + Cu(s)
C) K(s) + H2O(l)  KOH(aq) + H2(g)
D) H+(aq) + OH- (aq)  H2O(l)
E) CaCO3CaO + CO2
____ 3. What volume of 3.0 M NaOH can be prepared using exactly 96.0 g of NaOH?
A) 0.14 L
B) 0.70 L
C) 0.80 L
____ 4. How many milliliters of water must be added to 300 mL of 0.75 M HCl to dilute the solution to 0.25 M?
A) 900 mL
B) 600 mL
C) 300 mL
D) 930 mL
E) 100 mL
____ 5. Glycine, C2H5O2N, is important for biological energy. The combustion reaction of glycine is given by the equation
4C2H5O2N(s) + 9O2(g) → 8CO2(g) + 10H2O(l) + 2N2(g)
ΔH°rxn = –3857 kJ/mol
Given that ΔH°f[CO2(g)] = –393.5 kJ/mol and ΔH°f[H2O(l)] = –285.8 kJ/mol, calculate the enthalpy of formation of glycine.
A) –537.2 kJ/mol
B) –268.2 kJ/mol
D) –3,178 kJ/mol
C) 2,149 kJ/mol
E) –964 kJ/mol
____6. The specific heat of gold is 0.129 J/g·°C. What is the molar heat capacity of gold?
A) 0.039 J/mol·°C
B) 0.129 J/mol·°C
C) 25.4 J/mol·°C
D) 39.0 kJ/mol·°C
E) 197 J/mol·°C
C) 1.25 g/L
D) 2.50 g/L
E) None of the above.
D) 0.560 g
E) 1.08 g
____ 7. Calculate the density of nitrogen gas at STP.
A) 0.625 g/L
B) 0.800 g/L
____8. How many grams of carbon dioxide are contained in 550 mL of this gas at STP?
A) 0.0245 g
B) 0.0280 g
C) 1080 g
____9. Calculate the change in energy of the system for a process in which the system releases 1.79 J of heat to the surroundings and
does 4.51 cal (1 cal =4.184J) of work on the surroundings.
A) 6.30 J
B) 2.72 J
C) -20.7 J
D) 17.1 J
____10. In the following chemical reaction the oxidizing agent is
5H2O2 + 2MnO4– + 6H+ → 2Mn2+ + 8H2O + 5O2
A) O2
B) Mn+2
C) H+
2
D) MnO4-
E) H2O2
E) None of the above
____11. How much heat is evolved when 320 g of SO 2 is burned according to the chemical equation shown below?
2 SO2(g) + O2(g)  2 SO3(g) Horxn = -198 kJ
A) 5.04 x 10-2 kJ
B) 9.90 x 102 kJ
C) 207 kJ
D) 495 kJ
E) None of the above
____ 12. A 1.300 g sample of benzoic acid (C7H6O2) was burned in a bomb calorimeter. The heat capacity of the entire apparatus,
was found to be 11,145 J/K. As a result of the reaction, the temperature of the calorimeter and water increased 4.627 oC.
What is the molar heat of combustion of benzoic acid?
A) 4.84 x 106 kJ/mol
B) -2.96 kJ/mol
C) -4844 kJ/mol
D) 549.1 kJ/mol E) 51.57 kJ/mol
____ 13. What is the energy in joules of a mole of photons associated with red light of wavelength 7.00 × 10 2 nm?
A) 256 kJ
B) 1.71 × 105 J
C) 4.72 × 10-43 J D) 12.4 kJ
E) 2.12 × 1042 J
____ 14. Which of the following compounds is a weak electrolyte?
A) HNO3
B) NaNO3
C) HNO2
D) NaNO2
E) NaOH
____15. What is the chemical formula of the salt produced by the neutralization of hydrobromic acid with magnesium hydroxide?
A) MgBr
B) Mg2Br3
C) Mg3Br2
D) Mg2Br
E) MgBr2
D) Ne
E) all of them have the same velocity
D) ClO3-
E) Cl-
____ 16. Which of the following gas has the highest rms velocity at STP?
A) N2
B) O2
C) NO
____ 17. In which of the following is the oxidation number of Cl +1
A) Cl2
B) ClO-
C) ClO2-
____ 18. A 60.0 g sample of an alloy was heated to 96.00 oC and then dropped into a beaker containing 87.0 g of water at a temperature
of 24.10 oC. The temperature of the water rose to a final temperature of 27.63 oC. The specific heat of water is 4.184 J/g·oC.
What is the specific heat capacity of the alloy?
A) 0.313 J/g·oC
B) 2.16 J/g·oC
C) 0.118 J/g·oC D) 1.72 J/g·oC
E) None of the above.
____19. 1.018 g of Freon-113 gas is trapped in a 145 mL container at 760. mmHg and 50.0°C. What is the molar mass of Freon-113?
A) 21.7 g/mol
B) 28.8 g/mol
C) 46.1 g/mol
D)186 g/mol
____20. Nickel is more active than tin but less active than aluminum. Which one of the
following statements is true?
A. Al will reduce Ni & Sn
C. Al+3 will oxidize Ni & Sn
E. Al will oxidize Ni & Sn
B. Sn+2 will oxidize Al & Ni
D. Sn will reduce Ni+2, Al+3
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E) 245 g/mol
PART II- ( 5 points each) Please show all your work.
21. At 25°C, the following heats of reaction are known:
2ClF(g) + O2(g) → Cl2O(g) + F2O(g)
2ClF3(g) + 2O2(g) → Cl2O(g) + 3F2O(g)
2F2(g) + O2(g) → 2F2O(g)
ΔH°rxn = 167.4 kJ/mol
ΔH°rxn = 341.4 kJ/mol
ΔH°rxn = –43.4 kJ/mol
At the same temperature, use Hess's law to calculate ΔH°rxn for the reaction:
ClF(g) + F2(g) → ClF3(g)
22. A mixture of 14.0 grams of H2, 84.0 grams of N2, and 64.0 grams of O2 are placed in a flask. The partial pressure of
the O2 is 78.00 torr.
a. What is the total pressure in the flask?
b. What are the partial pressures of the remaining gases, H2 & N2
23. When 10.1 g CaO is dropped into a styrofoam coffee cup containing 157 g H 2O at 18.0°C, the temperature rises
to 35.8°C. Calculate the enthalpy change of the following reaction in kJ/mol CaO. Assume that the cup is a
perfect insulator and that the cup absorbs only a negligible amount of heat?
(the specific heat of water = 4.18 J/g·°C)
CaO(s) + H2O(l) → Ca(OH)2(s)
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24. A convenient way to produce very high purity oxygen in the laboratory is to decompose KMnO4(s) at high temperature according to
the following chemical equation:
2KMnO4(s) → K2MnO4(s) + MnO2(s) + O2(g)
If 2.50 L of O2(g) is needed at 1.00 atm and 20°C, what mass of KMnO 4(s) should be decomposed? Assume the decomposition of
KMnO4(s) goes to completion.
25. Consider the electronic transition from n = 7 to n = 4 in the hydrogen atom.
a. Is light absorbed or emitted?
b. Calculate the energy, the frequency and wavelength (in nm) of the photon involved.
Bonus Question ( 10 points) - Please show all your work
a. Write the balanced molecular equation & the net ionic equation for the neutralization reaction between H 3PO4(aq) and
Ba(OH)2(aq).
b. If 30.0 mL of 0.15 M Ba(OH)2 was needed to neutralize 50.0 mL of an H3PO4 solution. What is the concentration of the original
H3PO4 solution?
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Part I
1. Ar
15. E
2. D
16. D
3. C
17. B
4. B
18. A
5. A
19. D
6. C
20. B
7. C
8. E
9. C
Part II
21.
Divide equation 1 by 2
1. ClF + (1/2)O2  (1/2) Cl2O + (1/2)F2O
ΔH°rxn = 167.4/2 kJ = 83.70 kJ
Reverse and divide equation 2 by 2
2. (1/2)Cl2O(g) + (3/2)F2O(g) ClF3(g) + O2(g)
ΔH°rxn = -341.42 kJ = -170.71 kJ
Divide equation 3 by 2
3. F2 + (1/2) O2  F2O
ΔH°rxn = -43.4/2 kJ = -21.7kJ
10. D
11. D
12. C
13. B
14. C
Adding equation 1, 2, 3
. ClF + (1/2)O2+(1/2)Cl2O(g) + (3/2)F2O(g) + F2 + (1/2) O2  (1/2) Cl2O + (1/2)F2O+ F2O+ ClF3(g) + O2(g)
ΔH°rxn = 83.70 kJ + -170.71 kJ + -21.7 kJ = -108.71 kJ
22. a. PO2 =Pt × XO2
14.0 g H2 = 7.00 mol H2;
nt =12.00 mol;
78.00 torr = Pt × 2.00/12.00;
b.
84.0 g N2 = 3.00 mol N2;
64.0 g O2 = 2.00 mol O2
XO2 = 2.00/12.00
Pt = (12.00/2.00) × 78.00torr = 468 torr
PH2 =Pt × XH2 = 468 torr × (7.00/12.00) = 273 torr;
PN2 =Pt × XN2= 468 torr × (3.00/12.00) = 117 torr
23.
Mass of solution = 167.1 g
Specific heat of solution = 4.18 J/g·°C
Δt= (35.8 – 18.0) °C = 17.8 °C
qsolution = 167.1 g × 4.18 J/g·°C × 17.8 °C = 1.24 × 10 4 J
qrxn = -1.24 × 104 J =-12.4 kJ
10.1 g CaO = 0.180 mol CaO
qrxn in kJ/mol CaO = -12.4kJ/0.180 mol = -68.9 kJ/mol
24.
Moles of O2 produced = (1 atm × 2.50 L)/(0.0821 L atm K-1mol-1 × 293 K) = 0.104 moles
Moles of KMnO4 = 0.104 moles O2 × (2 moles KMnO4/1 mole O2) = 0.208 moles
Mass of KMnO4 = 0.208 moles × 158.04 g/mol =32.8 g
25.
a. emitted
b. ΔE = 2.18 × 10-18×(1/49 – 1/16) J = -9.18 × 10-20 J: energy released: energy of photon emitted = 9.18 × 10-20 J
Frequency of photon emitted = 9.18 × 10 -20 J/(6.63 × 10-34 Js) = 1.38 × 1014 s-1
Wavelength of photon emitted = 3.00 × 10 8 ms-1 /(1.38 × 1014 s-1) = 2.17 × 10-6 m = 2170 nm
Bonus Question ( 10 points) - Please show all your work
a. 2H3PO4(aq) + 3Ba(OH)2(aq) Ba3(PO4)2(s) + 6H2O(l)
b. If 30.0 mL of 0.15 M Ba(OH)2 was needed to neutralize 50.0 mL of an H3PO4 solution. What is the concentration of the original
H3PO4 solution?
Moles of Ba(OH)2 used = 0.0300 L × 0.15 M = 0.0045 moles
Moles of H3PO4 used = 0.0045 mole Ba(OH)2 × ( 2 moles H3PO4/3 moles Ba(OH)2) = 0.0030 moles H3PO4
Molarity of the H3PO4 = 0.0030 moles H3PO4/0.0500 L = 0.060 M
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