1992 - JAMB Chemistry Past Questions and Answers - page 3
21
Calculate the mass, in kilograms, of magnesium produced by the electrolysis of magnesium (II) chloride in a cell operating for 24 hours at 500 amperes.
A
2.7
B
5.4
C
10.8
D
21.7
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22
S2O2-3 + I2 → S2O62- + 2I-. In reaction above, the oxidizing agent is?
A
S2O32-
B
I2
C
S4O62-
D
I-
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23
MnO2 + 2CI- + 4H+ → MnO2+ + CI2 + 2H2O.
The changes is oxidation numbers when the manganese, chloride and hydrogen ions react according to the above equation are respectively?
The changes is oxidation numbers when the manganese, chloride and hydrogen ions react according to the above equation are respectively?
A
2, 2, 4
B
-1, -2, 4
C
-2, 1, 0
D
2, 4, 0
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24
In which of the following is the entropy change positive?
A
H2O(I) → H2O(g)
B
Cu2+(aq) + Fe(s) → Fe(2+) + Cu(s)
C
N2(g) + 3H2(g) → 2NH3(g)
D
2HCI(s) → H2(g) + CI2(g)
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25
In what way is equilibrium constant for the forward reaction related to that of the reversed reaction?
A
The additional of the two is expected to be one
B
The product of the two is expected to be one
C
The two equilibrium constants are identical
D
The product of the two is always greater than one
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26
Which of the following equilibria shows little or no net reaction when the volume of the system is decreased?
A
H2(g) + I2(g) ≈ 2HI(g)
B
2NO2(g) ≈ N2O4(g)O4(g)N2O4(g)
C
PCI5(g) ≈ PCI3(g) + CI2(g)
D
ZnO(s) + CO2(g) ≈ ZnCO3(g)
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27
For a general equation of the nature xP + yQ ≈ mR + nS, the expression for the equilibrium constant is?
A
k (p)x (Q)y
B
(p)x (Q)y / (R)m (S)n
C
(R)m (S)n / (p)x (Q)y
D
m(R) n (S) / x(P) y (Q)
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28
Which of these statements is TRUE about carbon (IV) oxide?
A
it supports combustion
B
It is strongly acidic in water
C
It is very soluble in water
D
It supports the buring of magnesium to produce magnesium oxide
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29
Which of the following combination of gases is used for metal welding? i. Oxygen and ethyne, ii. Hydrogen and ethyne, iii. Hydrogen and oxygen, iv. Ethyne, hydrogen and oxygen.
A
i and ii
B
ii and iv
C
i and iii
D
ii and iv
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30
Which of the following oxides of nitrogen is unstable in air?
A
NO2
B
NO
C
N2O4
D
N2O5-
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