1990 - JAMB Chemistry Past Questions and Answers - page 1
1
Which of the following is a physical change?
A
The bubbling of chlorine into water
B
The bubbling of chlorine into a jar contanining hydrogen
C
The dissolution of sodium chloride in water
D
The passing of steam over heated iron
correct option: c
Users' Answers & Comments2
In a reaction: SnO + 2C → Sn + 2CO, the mass of coke containing 80% carbon required to reduce 0.302 kg of pure tin oxide is?
(Sn - 119, O - 16, C - 12).
(Sn - 119, O - 16, C - 12).
A
0.40 kg
B
0.20 kg
C
0.06 kg
D
0.04 kg
correct option: c
In the reaction: SnO2 + 2CO
From the equation above
2(12 g) carbon = 151 g SnO2
24 g carbon =151 g SnO2
= 0.302 kg SnO2 = 24/151g χ 0.0302 kg carbon = 0.048 kg carbon
Mass of coke is required not mass of carbon,so it is (0.048\(\times\)100)\(\div\)80 = 0.06
Users' Answers & CommentsFrom the equation above
2(12 g) carbon = 151 g SnO2
24 g carbon =151 g SnO2
= 0.302 kg SnO2 = 24/151g χ 0.0302 kg carbon = 0.048 kg carbon
Mass of coke is required not mass of carbon,so it is (0.048\(\times\)100)\(\div\)80 = 0.06
3
Cr2O7 + 6Fe2+ + 14H+ → 2Cr3+ +6Fe3+ + 7H2O. In the above , the oxidation number of chromium changed from?
A
+7 to +3
B
+6 to +3
C
+5 to +3
D
-2 to +3
correct option: a
Users' Answers & Comments4
In the reaction 1O-3 + 5l- + 6H+ → 312 + 3H2O, the oxidizing agent is?
A
H+
B
l-
C
1O-
D
l2
correct option: c
Users' Answers & Comments5
Fe2O3(s) + 2Al(s) → Al2O3 + 2Fe(s) If the heats of formation of Al2O3 and Fe2O3 are - 1670 kj mol-1 and - 822 kj mol-1 respectively, the enthalpy change in kj for the reaction is ?
A
+2492
B
+848
C
-848
D
-2492
correct option: c
Users' Answers & Comments6
Iron galvanized with zinc is cathodically protected from corrosion. This is because?
A
zinc has a more positive oxidation potential than iron
B
zinc has less positive oxidation potential than iron
C
bith have the same oxidation potential
D
zinc is harder than iron
correct option: b
Users' Answers & Comments7
Which of the following samples will react fastest with dilute trioxonitrate (V) acid?
A
5 g of lumps of CacO3 at 25°C
B
5 g of powered CacO3 at 25°
C
5 g of lumps of CaCO3 at 50°C
D
5 g of powered CaCO3 AT 50°C
correct option: d
Users' Answers & Comments8
In the reaction:
2Hl(g) ↔ H2(g) + l2(g)' ΔH = 10 kj;
The concentration of iodine in the equilibrium mixture can be increased by?
2Hl(g) ↔ H2(g) + l2(g)' ΔH = 10 kj;
The concentration of iodine in the equilibrium mixture can be increased by?
A
raising the pressure
B
raising the temperature
C
adding a catalyst
D
lowering the pressure
correct option: b
Users' Answers & Comments9
Which of the following gases can be collected by the upward displacement of air?
A
NO
B
H 2
C
NH3
D
Cl 2
correct option: d
Users' Answers & Comments10
The brown fumes given off when trioxonitrate (V) acid is heated consist of ?
A
NO2 and O2
B
H2O and NO2
C
NO2' O2 and H2O
D
NO, NO2 and H2O
correct option: c
Users' Answers & Comments