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
correct option: b
Mg + 2e → 24 gms
2f → 24 gms
2 x 96,500 → 24 gms
Q = (500 x 1440 x 60)
Q = 4320000 C
1 mole of mg = (1) / (2 x 96,500) x (43200000) / (1)
= (24)/(1) = (1036800000) / (193000) = 5372.020725 gms
in leg = (5372.020725) / (1000) = 5.4 leg
Users' Answers & Comments2f → 24 gms
2 x 96,500 → 24 gms
Q = (500 x 1440 x 60)
Q = 4320000 C
1 mole of mg = (1) / (2 x 96,500) x (43200000) / (1)
= (24)/(1) = (1036800000) / (193000) = 5372.020725 gms
in leg = (5372.020725) / (1000) = 5.4 leg
22
S2O2-3 + I2 → S2O62- + 2I-. In reaction above, the oxidizing agent is?
A
S2O32-
B
I2
C
S4O62-
D
I-
correct option: b
Users' Answers & Comments23
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
correct option: c
Users' Answers & Comments24
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)
correct option: a
Users' Answers & Comments25
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
correct option: a
Users' Answers & Comments26
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)
correct option: d
Users' Answers & Comments27
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)
correct option: c
Users' Answers & Comments28
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
correct option: c
Users' Answers & Comments29
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
correct option: a
Users' Answers & Comments30
Which of the following oxides of nitrogen is unstable in air?
A
NO2
B
NO
C
N2O4
D
N2O5-
correct option: b
Users' Answers & Comments