1997 - JAMB Chemistry Past Questions and Answers - page 2
11
200 cm3 of air was passed over heated copper in a syringe several times to produce copper (II) oxide.
When cooled, the final volume of air recorded was 158cm3. Estimate the percentage of oxygen in the air?
When cooled, the final volume of air recorded was 158cm3. Estimate the percentage of oxygen in the air?
A
31%
B
27%
C
21%
D
19%
correct option: c
Volume of O2 used = 200 - 158 = 42 cm3
% of O2 = (42)/(200) x 100% = 21%
Users' Answers & Comments% of O2 = (42)/(200) x 100% = 21%
12
On recrystallization, 20g of magnesium tetraoxosuphate (IV) forms 41 g of magnesium tetraoxosulphate (IV) crystals, MgSO4. yH2O. The value of y is?
(Mg = 24, S = 32, O = 16, H = 1)
(Mg = 24, S = 32, O = 16, H = 1)
A
1
B
3
C
5
D
7
correct option: d
MgSO4. YH2O
120g (MgSo4) contains - 18g (water)
20g contain (41 - 20g) water.
120g → 18 y; 20 → 21
∴ 18 y = (126)/(18) = 7
Users' Answers & Comments120g (MgSo4) contains - 18g (water)
20g contain (41 - 20g) water.
120g → 18 y; 20 → 21
∴ 18 y = (126)/(18) = 7
13
Which of the following gases is the most dangerous pollutant?
A
Hydrogen sulphide
B
Carbon (lV) oxide
C
Sulphur (lV) oxide
D
Carbon (ll) oxide
correct option: d
Carbon monoxide is a colourless, odourless and tasteless gas that is produced by the incomplete combustion of fossil fuel. It is the most dangerous of all the pollutant gases and can cause death in very high concentrations.
Users' Answers & Comments14
A major process involved in the softening of hard water is the?
A
conversation of a soluble calcium salt to its trioxoncarbonate (lV)
B
decomposition of calcium rioxocarbonate (lV)
C
conversion of an insoluble calcium salts to its trioxocarbonate (lV)
D
oxidation of calcium atoms to its ions
correct option: a
Users' Answers & Comments15
A saturated solution of AgCl was found to have a concentration of 1.30 x 10-5 mol dm-3. The solubility product of AgCl therefore is?
A
1.30 x 10-5 mol2 dm-6
B
1.30 x 10-7 mol2 dm-6
C
1.69 x 10-10 mol2 dm-6
D
2.60 x 10-12 mol2 dm-6
correct option: c
Users' Answers & Comments16
The hydroxyl ion concentrated, (OH-), in a solution of sodium hydroxide of pH 10.0 is?
A
10-10 mol dm-3
B
10-6 mol dm-3
C
10-4 mol dm-3
D
10-2 mol dm-3
correct option: c
Users' Answers & Comments17
Which of the aqueous solutions with the pH values below will liberate hydrogen when it react with magnesium metals?
A
13.0
B
7.0
C
6.5
D
3.0
correct option: d
Users' Answers & Comments18
Given that 15.00 cm3 of H2
SO4 was required to completely neutralize 25.00 cm3 of 0.125 mol dm-3 NaOH, calculate the molar concentration of the acid solution:
SO4 was required to completely neutralize 25.00 cm3 of 0.125 mol dm-3 NaOH, calculate the molar concentration of the acid solution:
A
0.925 mol dm-3
B
0.156mol dm-3
C
0.104 mol dm-3
D
0.023 mol dm-3
correct option: c
H2SO4 + 2NaOH → Na2SO4 + 2H2O
(MaVa)/(MBVB) (1)/(2) (MA x 15)/(0.125 x25) = 1/2
MA = 0.104
Users' Answers & Comments(MaVa)/(MBVB) (1)/(2) (MA x 15)/(0.125 x25) = 1/2
MA = 0.104
19
When platinum electrodes are used during the electrolysis of copper (ll) tetraoxosulphate (lV) solution, the solution gets progressively?
A
acidic
B
basic
C
neutral
D
amphoteric
correct option: a
Users' Answers & Comments20
How many Faraday of electricity are required to deposit 0.20 mole of nickel, if 0.10 Faraday of electricity deposited 2.98g of nickel during electrolysis of its aqueous solution?
(Ni = 58.7, 1F = 96 500 C mol-)
(Ni = 58.7, 1F = 96 500 C mol-)
A
0.20
B
0.30
C
0.40
D
0.50
correct option: c
No of mole → (2.98)/(58.7) ..............0.1
2.0 .................x
∴ x = (0.2)/(2.98) x 58.7 x 0.40
Users' Answers & Comments2.0 .................x
∴ x = (0.2)/(2.98) x 58.7 x 0.40