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JAMB Chemistry Past Questions & Answers - Page 89

441.

The following arrangement of elements in order of decreasing number of outer electrons; One of the elements is wrongly placed. Which is it? ALUMINIUM, CHLORINE, SILICON, MAGNESIUM AND SODIUM.

A.

chlorine

B.

aluminium

C.

silicon

D.

magnesium

E.

sodium

View answer & explanation

Correct answer is B

No explanation has been provided for this answer.

442.

Which of the following represents a precipitation reaction?

A.

H₂SO₄ + NaCl $\to$ NaHSO₄ + HCl

B.

Fe +H₂SO₄ $\to$ FeSO₄ + H₂

C.

4HCl + MnO₂ $\to$ MnCl₂ + 2H₂O + Cl₂

D.

Na₂SO₄ + pb(NO₃) $\to$ PbSO₄ + 2NaNO

E.

CuO +2HCl $\to$ Cl₂ + H₂O

View answer & explanation

Correct answer is D

No explanation has been provided for this answer.

443.

1.00g of mixture of calcium carbonate and calcium oxide liberated 0.33g of carbon dioxide on strong heating. The percentage of calcium oxide in the mixture is? (Ca = 40, C = 12, O = 16)

A.

5

B.

15

C.

25

D.

35

E.

50

View answer & explanation

Correct answer is C

CaCO₃ + CaO $\to$ 2CaO + 2CO₂

44gm of CO₃ is liberated by 100gm of CaCO₃

0.33gm of CO₂ will be liberated by $\frac{100}{44}$ x 0.33

= 0.75 of CaCO₃

Amount of CaO = 1 - 0.75

= 0.25

% of CaO = $\frac{0.25}{1} \times \frac{100}{1}$

= 25%

444.

In the experiment above, a current was passed for 10 minutes, and 0.63g of copper was found to be deposited on the cathode of CuSO4 cells. The weight of silver deposited on the cathode of AgNO3 cell during the same period would be? [Cu = 63, Ag = 108]

A.

0.54g

B.

1.08g

C.

1.62g

D.

2.16g

E.

3.24g

View answer & explanation

Correct answer is D

Same period, Same current

$Cu^{2+} + 2e^- → Cu; 2Ag^+ + 2e^-$ → Ag

From the equation above, 2 mol Ag ≡ 1 mol Cu

But 0.63g Cu = $\frac{0.63}{63}$ = 0.01mole Cu

Hence 0.002 mole Ag is deposited

mass of Ag deposited = 0.002 x 108 = 2.16g.

445.

In the above experiment, the litmus paper will initially

A.

be bleached

B.

turn green

C.

turn red

D.

turn blue

E.

turn black

View answer & explanation

Correct answer is D

No explanation has been provided for this answer.

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