Chemistry Essay
Chemistry
1. Consider the reaction:
2 MnO4- + 5 CH3CHO + 6 H+ —> 5 CH3COOH + 2 Mn2+ + 3 H2O
The reducing agent is
A. Mn2+
B. MnO4-
C. CH3CHO
D. CH3COOH
2. The equation, Al —> Al 3+ + 3 e – represents
A. oxidation.
B. reduction.
C. electrolysis.
D. displacement.
3. Consider the following observations:
Co 3+ + Ce 3+ —> Co 2+ + Ce 4+
Co 2+ + Au 3+ —> NO REACTION
6 Br – + 2 Au 3+ —> 2 Au + 3 Br2
Au 3+ + Ce 3+ —> NO REACTION
The oxidizing agents in order (starting with the strongest) are
A. Br2 , Au 3+ , Ce 4+ , Co 3+
B. Co 3+ , Ce 4+ , Au 3+ , Br2
C. Ce 4+ , Co 3+ , Au 3+ , Br2
D. Ce 4+ , Au 3+ , Co 2+ , Br2
4. Using the table of standard reduction potentials, it can be predicted that I – will react spontaneously with
A. Co
B. Br2
C. Cl –
D. Cu2+
5. The oxidation number of oxygen in Na2O2 is
A. 0
B. – 1
C. – 2
D. – 4
6. Consider the reaction:
3 C3H8O + Cr2O72- + 8 H+ —> 3 C3H6O + 2 Cr3+ + 7 H2O
The oxidation number of C is changed by
A. + 2/3
B. +2
C. – 2/3
D. -2
7. Consider the cell below:
Consider the cell below for questions 8 and 9.
8. The flow of electrons is from
A. Pb to Mn through the wire.
B. Mn to Pb through the wire.
C. Pb to Mn through the salt bridge.
D. Mn to Pb through the salt bridge.
9. As the cell operates,
A. [Pb2+] and [Mn2+] increase.
B. [Pb2+] and [Mn2+] decrease.
C. [Pb2+] increases as [Mn2+] decreases.
D. [Pb2+] decreases as [Mn2+] increases.
10. Consider the following half-reactions:
Cd2+ + 2 e – —> Cd Eo = – 0.40 V
Nb3+ + 3 e – —> Nb Eo = – 1.10 V
When the cell below is connected, the initial Eo value is
A. – 1.50 V
B. – 0.70 V
C. + 0.70 V
D. + 1.50 V
11. As iron corrodes in moist air,
A. the iron loses electrons.
B. water is oxidized.
C. the iron acts as an oxidizing agent.
D. oxygen donates electrons to metal ions.
12. Consider the following:
PbO2 + Pb + 4 H+ + 2 SO4 2- —> 2 PbSO4 + 2 H2O
The substance which loses electrons is
A. Pb
B. PbO2
C. H+
D. SO4 2-
13. Which of the following is the strongest reducing agent?
A. cobalt
B. copper
C. calcium
D. chromium
14. Which of the following species will react with Cl2 but not with Br2 ?
A. Mn
B. acidified Mn2+
C. acidified MnO2
D. acidified MnO4 –
15. Consider the following:
ClO4- + 4 Mn2+ + 4 H2O —> Cl – + 8 H+ + 4 MnO2
The forward reaction is
A. spontaneous and the E° is + 0.17 V
B. spontaneous and the E° is – 0.17 V
C. non-spontaneous and the E° is + 0.17 V
D. non-spontaneous and the E° is – 0.17 V
16. Consider the following:
3 C3H8O + 2 CrO3 + 3 H2SO4 —> 3 C3H6O + 6 H2O + Cr2 (SO4)3
The oxidation number of the chromium
A. increases as it undergoes reduction.
B. increases as it undergoes oxidation.
C. decreases as it undergoes oxidation.
D. decreases as it undergoes reduction.
17. Consider the following:
NO3 – —> NH4 +
The balanced half-reaction is
A. NO3 – + 10 H+ + 9e – —> NH4+ + 3 H2O
B. NO3 – + 7 H+ + 8e – —> NH4+ + 3 OHC.
NO3 – + 6 H+ + 4e – —> NH4+ + 3 H2O
D. NO3 – + 10 H+ + 8e – —> NH4+ + 3 H2O
Use the following cell diagram for questions 18, 19 and 20.
18. In the above electrochemical cell,
A. the mass of the anode increases and the mass of the cathode increases.
B. the mass of the anode decreases and the mass of the cathode decreases.
C. the mass of the anode decreases and the mass of the cathode increases.
D. the mass of the anode increases and the mass of the cathode decreases.
19. In the above electrochemical cell,
A. electrons migrate into the salt bridge.
B. the zinc ions migrate into the salt bridge.
C. the chloride ions migrate into the salt bridge.
D. the copper(II) ions migrate into the salt bridge.
20. In the operating electrochemical cell above, the initial voltage is
A. -1.10 V
B. -0. 42 V
C. 0.00 V
D. +1.10 V
21. The substance formed at the anode during the electrolysis of 1.0 M NaI is
A. iodine.
B. oxygen.
C. sodium.
D. hydrogen.
22. When molten aluminum oxide is electrolyzed, the cathode reaction is
A. Al —> Al 3+ + 3 e-
B. Al 3+ + 3 e- —> Al
C. O2 + 4 e- —> 2 O 2-
D. 2 O 2- —> O2 + 4e –
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