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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?

A
31%
B
27%
C
21%
D
19%
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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)

A
1
B
3
C
5
D
7
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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
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14

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
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15

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
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16

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
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17

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
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18

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:

A
0.925 mol dm-3
B
0.156mol dm-3
C
0.104 mol dm-3
D
0.023 mol dm-3
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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
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20

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-)

A
0.20
B
0.30
C
0.40
D
0.50
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