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UTME Chemistry 1997 JAMB Past Questions and Answers, Jamb, Pre-degree, Nursing, Waec, Neco

UTME Chemistry 1997 JAMB Past Questions and Answers, Jamb, Pre-degree, Nursing, Waec, Neco

UTME Chemistry 1997 JAMB Past Questions and Answers

1. 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?

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Options

A) 31%

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B) 27%

C) 21%

D) 19%

The correct answer is C.

Explanation:

Volume of O2 used = 200 – 158 = 42 cm3

% of O2 = (42)/(200) x 100% = 21%

2. 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)

Options

A) 1

B) 3

C) 5

D) 7

The correct answer is D.

Explanation:

MgSO4. YH2O

120g (MgSo4) contains – 18g (water)

20g contain (41 – 20g) water.

120g → 18 y; 20 → 21

∴ 18 y = (126)/(18) = 7

3. An element, X, forms a volatile hydride XH3 with a vapour density of 17.0. The relative atomic mass of X is?

(H = 1)

Options

A) 34.0

B) 31.0

C) 20.0

D) 14.0

The correct answer is B.

Explanation:

Molecular Mass = Vapour density x 2 = 17.0 x 2 = 34.0

∴ Relative Atomic Mass of X in XH3 = 34 – 3

= 31.0 ∴ x = 31.0

4. A mixture of 0.20 mole of Ar, 0.20 mole of N2 and 0.30 mole of He exerts a total pressure of 2.1 atm. The partial pressure of He in the mixture is?

Options

A) 0.90 atm

B) 0.80 atm

C) 0.70 atm

D) 0.60 atm

The correct answer is A.

Explanation:

Total no mole = 0.2 + 0.2 + 0.3 = 0.7

Partial pressure of He = (0.3)/(0.7) x 2.1 =0.90

5. The temperature of a body decreases when drops of liquid placed on it evaporate because?

Options

A) the atmospheric vapour pressure has a cooling effect on the body

B) a temperature gradient exists between the drops of liquid and the body causing the latter to vaporate

C) the heat of vapourization is drawn from the body causing it to cool

D) the random motion of the liquid molecules causes a cooling effect on the body

The correct answer is C.

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