JAMB Chemistry Past Questions & Answers - Page 321

1,601.

A sample of an oxide of mercury weighed 1.00g. When this was heated, oxygen was given off, and 1.00g of mercury metal only was left. What is the formula of the oxide?

A.

Hg2O

B.

HgO2

C.

HgO2

D.

HgO

E.

None of the above

Correct answer is E

Various oxides of mercury: Mercury(I) oxide (mercurous oxide), Hg\(_2\)OMercury(II) oxide (mercuric oxide), HgO.

No specific oxide of mercury is refered in the question. 

1,602.

10cm3 of CO is mixed and sparked with 100cm3 of air containing 21% O2. If all the volumes measured at S.T.P. the volume of resulting gases would be?

A.

90cm3

B.

100cm3

C.

105cm3

D.

110cm3

E.

115cm3

Correct answer is C

2CO(g) + O2(g) ---> 2CO\(_2\)(g)
2vol 1vol 2vol
Volume in cm\(^3\) Before sparking: 10 // 21
Volume in cm\(^3\) On sparking 10 // 5 // 10
Volume in cm\(^3\) After sparking: 0// 16 // 10
Total volume of resulting gas = Volume of [excess oxygen + CO\(_2\) produced + unreactive components]
= 16 + 10 + 79   → 105cm\(^3\)

1,604.

The alloy duralumin is used for the building of aeroplanes because it?

A.

asborbs heat readily from sure thereby preventing the inside of the plane from getting cold at high attitudes

B.

reflects sunlight readily, thereby keeping the inside of the plane cool

C.

is extremely durable and possesses reflective ability

D.

is easily the lightest building material

E.

possesses both strenght and lightness

Correct answer is E

No explanation has been provided for this answer.

1,605.

In an attempt to remove sugar from a breaker containing a quantity of sand and sugar, 2 M ammonium chloride solution was accidentally added instead of water. Which of the following method could be used to remove the ammonium chloride from the mixture?

A.

Fractional distillation

B.

crystallization

C.

Filtration followed by evaporation

D.

Evaporation followed by sublimation

E.

Filtration followed by sublimation

Correct answer is D

No explanation has been provided for this answer.