JAMB Chemistry Past Questions & Answers - Page 310

1,546.

In a reaction: \(SnO_{2} + 2C → Sn + 2CO\) the mass of coke containing 80% carbon required to reduce 0.302 kg of pure tin oxide is?
(Sn - 119, O - 16, C - 12).

A.

0.40 kg

B.

0.20 kg

C.

0.06 kg

D.

0.04 kg

Correct answer is C

In the reaction: \(SnO_{2} + 2CO\)
From the equation above
2(12 g) carbon = 151 g \(SnO_{2}\)

24 g carbon =151 g \(SnO_{2}\)
= 0.302 kg \(SnO_{2}\) = 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

1,547.

Which of the following statements is true?

A.

Metals conduct electricity while non-metals do not

B.

Metals have high density, non-metals have low density

C.

Metals form basic oxides, non-metals form acidic oxides

D.

In the electro chemical series, metals are above hydrogen while non-metals are below hydrogen

E.

Metals lose elections while non-metals gain electron during chemical reactions

Correct answer is E

- Chemical reactions in which electrons are transferred are called oxidation-reduction, or redox, reactions. Oxidation is the loss of electrons. Reduction is the gain of electrons. Oxidation and reduction always occur together, even though they can be written as separate chemical equations. -The most common reducing agents are metals, for they tend to lose electrons in their reactions with nonmetals. Option E is most appropriate.

1,548.

Which of the following statements is an exception in the assumptions of the kinetic theory of gases?

A.

Gases are composed of many elastic particles

B.

The particles are of negligible size

C.

The particles are in constant random motion

D.

The particles are of negligible mass

E.

The particles collide with each other

Correct answer is D

No explanation has been provided for this answer.

1,549.

How many grams of hydrogen gas will be liberated when 6g of magnesium ribbon dissolves in 500cm3 of 6M HCl?


(Mg=24, H=1, Cl=35.5)

A.

1.2 g

B.

0.7 g

C.

0.5 g

D.

0.3 g

E.

0.12 g

Correct answer is C

Mg + 2HCl → MgCl2 + H2
6 molar contains 6 Χ 36.5 gms 1000 cc

Solution i.e 6 Χ 36.5/2gms in 500 cc
= 3 Χ 36.5
24 gms of mg will react with 2 Χ 36.5 HCl to liberate 2 gm of hydrogen
∴ 6 gms will liberate 6 Χ 2/24 Χ 1 = 0.5 gm of H2

1,550.

Under high pressure, real gases do not obey gas laws because their molecules?

A.

have become more energetic

B.

have become less energetic

C.

have become smaller in size

D.

decompose into atoms

E.

start repelling each other

Correct answer is A

Van der Waals noticed the behavior of real gases at low temperature and high pressure possesses weak but short range forces.