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Which structure do you predict the
amino acid lysine to have at pH 7.4?
1. Structure A
2. Structure B
3. Structure C
4. Structure D
5. Structure E
+H3N CH C
CH2
OH
O
CH2
CH2
CH2
NH3+
+H3N CH C
CH2
O-
O
CH2
CH2
CH2
NH3+
pKa =2.2pKa =9.0
pKa = 10.5
Structure A Structure B
Structure C Structure D Structure E
H2N CH C
CH2
O-
O
CH2
CH2
CH2
NH3+
H2N CH C
CH2
OH
O
CH2
CH2
CH2
NH2
+H3N CH C
CH2
O-
O
CH2
CH2
CH2
NH2
1
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Which structure do you predict the
amino acid lysine to have at pH 7.4?
9%
19%
7%
54%
11% 1. Structure A
2. Structure B
3. Structure C
4. Structure D
5. Structure E
+H3N CH C
CH2
OH
O
CH2
CH2
CH2
NH3+
+H3N CH C
CH2
O-
O
CH2
CH2
CH2
NH3+
pKa =2.2pKa =9.0
pKa = 10.5
Structure A Structure B
Structure C Structure D Structure E
H2N CH C
CH2
O-
O
CH2
CH2
CH2
NH3+
H2N CH C
CH2
OH
O
CH2
CH2
CH2
NH2
+H3N CH C
CH2
O-
O
CH2
CH2
CH2
NH2
2
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What is the oxidation number of nitrogen in N2O?
1. -2 2. -1 3. 0 4. +1 5. +2
3
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What is the oxidation number of nitrogen in N2O?
1. -2 2. -1 3. 0 4. +1 5. +2
1. 2. 3. 4. 5.
3% 4% 2%
88%
3%
4
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For the half reaction: Cr2O7
2- → Cr3+ Cr is…
1. Reduced (it loses electrons) 2. Reduced (it gains electrons) 3. Oxidized (it loses electrons) 4. Oxidized (it gains electrons)
5
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For the half reaction: Cr2O7
2- → Cr3+ Cr is…
2%
10%
78%
9% 1. Reduced (it loses electrons) 2. Reduced (it gains electrons) 3. Oxidized (it loses electrons) 4. Oxidized (it gains electrons)
6
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Another cell has utilizes the following redox reactions:
Zn (s) → Zn2+ (ag) + 2e-
Sn4+ (ag) + 2e- → Sn2+ (ag)
which of the following is likely to be true?
1. anode: Zn(s) → Zn2+(aq) + 2e- (reduction) cathode: Sn4+(aq) + 2e- → Sn2+(aq) (oxidation)
2. anode: Zn(s) → Zn2+(aq) + 2e- (oxidation) cathode: Sn4+(aq) + 2e- → Sn2+ (aq) (reduction)
3. anode: Sn4+(aq) + 2e- → Sn2+(aq) (oxidation) cathode: Zn(s) → Zn2+(aq) + 2e- (reduction)
4. anode: Sn4+(aq) + 2e- → Sn2+ (aq) (reduction) cathode: Zn(s) → Zn2+(aq) + 2e- (oxidation)
7
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Another cell has utilizes the following redox reactions:
Zn (s) → Zn2+ (ag) + 2e-
Sn4+ (ag) + 2e- → Sn2+ (ag)
which of the following is likely to be true?
5%
3%
89%
4%1. anode: Zn(s) → Zn2+(aq) + 2e- (reduction)
cathode: Sn4+(aq) + 2e- → Sn2+(aq) (oxidation) 2. anode: Zn(s) → Zn2+(aq) + 2e- (oxidation)
cathode: Sn4+(aq) + 2e- → Sn2+ (aq) (reduction) 3. anode: Sn4+(aq) + 2e- → Sn2+(aq) (oxidation)
cathode: Zn(s) → Zn2+(aq) + 2e- (reduction) 4. anode: Sn4+(aq) + 2e- → Sn2+ (aq) (reduction)
cathode: Zn(s) → Zn2+(aq) + 2e- (oxidation)
8
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Predict the correct expression for the electrochemical cell:
Anode: Zn (s) → Zn2+ (aq) + 2e-
Cathode: Sn4+ (aq) + 2e- → Sn2+ (aq)
1. Zn (s) | Zn2+ (aq) || Sn4+ (aq) | Sn2+ (s)
2. Zn (s) | Zn2+ (aq) || Sn4+ (aq) | Sn2+ (aq)
3. Zn (s) | Zn2+ (aq) || Sn4+ (aq), Sn2+ (aq)
4. Zn (s) | Zn2+ (aq) | Sn4+ (aq) | Sn2+ (aq)
5. Zn (s) || Zn2+ (aq) || Sn4+ (aq) || Sn2+ (aq)
9
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Predict the correct expression for the electrochemical cell:
Anode: Zn (s) → Zn2+ (aq) + 2e-
Cathode: Sn4+ (aq) + 2e- → Sn2+ (aq)
1%
3%
35%
41%
19% 1. Zn (s) | Zn2+ (aq) || Sn4+ (aq) | Sn2+ (s)
2. Zn (s) | Zn2+ (aq) || Sn4+ (aq) | Sn2+ (aq)
3. Zn (s) | Zn2+ (aq) || Sn4+ (aq), Sn2+ (aq)
4. Zn (s) | Zn2+ (aq) | Sn4+ (aq) | Sn2+ (aq)
5. Zn (s) || Zn2+ (aq) || Sn4+ (aq) || Sn2+ (aq)
10
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What must be happening when
Pt (s) | H2 (g) | H+ (aq) acts as an anode?
1. Pt (s) is oxidized
2. H2 (g) is oxidized
3. H+ (aq) is oxidized
4. Pt (s) is reduced
5. H2 (g) is reduced
6. H+ (aq) is reduced
10 11
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What must be happening when
Pt (s) | H2 (g) | H+ (aq) acts as an anode?
17%
17%
17%
17%
17%
17% 1. Pt (s) is oxidized
2. H2 (g) is oxidized
3. H+ (aq) is oxidized
4. Pt (s) is reduced
5. H2 (g) is reduced
6. H+ (aq) is reduced
10 12
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5.111 Principles of Chemical ScienceFall 2014
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