1998 - JAMB Chemistry Past Questions & Answers - page 1

1
The addition of water to calcium oxide leads to?
A
a physical change
B
a chemical change
C
the formation of a mixture
D
an endothermic change
CORRECT OPTION: b
2
A mixture of iron and sulphur can be separated by dissolving the mixture in?
A
steam
B
dilute hydrochloric acid
C
dilute sodium hydroxide
D
benzene
CORRECT OPTION: d
3
A given amount of gas occupies 10.0 dm3 at atm, and 273°C. The number of moles of the gas present is?
(Molar volume of a gas at s.t.p. = 22.4 dm3)
A
0.89 mol
B
1.90 mol
C
3.80 mol
D
5.70 mol
CORRECT OPTION: b
4
8.0 g of an element X react with an excess of copper (ll) tetraoxosulphate (lV) solution to deposit 21.3 g of copper. The correct equation for the reaction is?

(Cu = 64).
A
X(s) + CuSO4(aq) → Cu(s) + XSO4(aq)
B
X(s) + 2CuSO4(aq) → 2Cu(s) + X(SO4)2(aq)
C
2X(s) + CuSO4(aq) → Cu(s) + X2SO4(aq)
D
2X(s) + 3CuSO4(aq) → 3Cu(s) + X2(SO4)3(aq)
CORRECT OPTION: a
5
C3H8(g) + 502(g) → 4H2O + 3CO2(g). Form the equation above the volume of oxygen at s.t.p. required to burn 50cm3 of propane is?
A
250 cm3
B
150 cm3
C
100 cm 3
D
50 cm3
CORRECT OPTION: a
C3H8 + 502 → 4H2O + 3CO2.
From the equation above 1 dm3 of C3H8 require 5dm3 of O2 at s.t.p.
∴ 50cm3 of C3H8 require x = (50) / (1000) x 5 x 1
x = (250) / (1000)
x = 250cm
6
30cm3 of hydrogen was collected over water at 27°C and 780 mm Hg. If the vapour pressure of water at the temperature of the experiment was 10 mm Hg, calculate the volume of the gas at 760 mm Hg and 7°C?
A
40.0 cm3
B
35.7 cm3
C
28.4 cm3
D
25.2 cm3
CORRECT OPTION: c
Y1 = 30cm3 T1 = 27 + 273 = 300K and P1 = (780 - 10)mm Hg i.e the pressure minus the vapour pressure of water
P2 = 760mm Hg and T2 = 7 + 273 = 280K
From (P2V2) / (T2) = (P1V1) / (T1)
(770 x 30) / (300) = (760 x O2) / (280)
V2 = (770 x 30x 280) / (300 x 760)
V2 = 28.4 cm3
7
If sulphur (IV) oxide and methane are released simultaneously at the opposite ends of a narrow tube, the rates of diffusion Rso2 and Rch4 will be in the ratio?

(S = 32, O = 16, C = 12, H = 1)
A
4:1
B
2:1
C
1:2
D
1:4
CORRECT OPTION: c
8
A solid begins to melt when?
A
constituent particles acquires a greater kinetic energy
B
energy of vibration of particles of the solid is less than the intermolecular forces
C
constituent particles acquires energy above the average kinetic energy
D
energy of vibration of particles of the solid equals the intermolecular forces
CORRECT OPTION: a
9
Which of the following electron configurations indicates an atom with the highest ionization energy?
A
2,8,7
B
2,8,8,1
C
2,8,8,2
D
2,8,8,7
CORRECT OPTION: a
10
The line observed in the sample hydrogen spectrum are due to emission of?
A
electrons from the atoms
B
energy by proton transition
C
energy by electron transition
D
neutron from the atom
CORRECT OPTION: c
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