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JAMB Chemistry Past Questions & Answers - Page 47

231.

Elements in the periodic table are arranged in the order of their

A.

atomic numbers

B.

metallic character

C.

mass number

D.

relative atomic mass

Correct answer is A

No explanation has been provided for this answer.

232.

Which important nitrogen-containing compound is produced in Haber's process?

A.

NH3

B.

NO2

C.

NO

D.

HNO3

Correct answer is A

No explanation has been provided for this answer.

233.

What mass of magnesium would be obtained by passing a current of 2 amperes for 2 hours 30 mins, through molten magnesium chloride?
[1 faraday = 96500C, Mg = 24]

A.

1.12g

B.

4.48g

C.

1.80g

D.

2.00g

Correct answer is D

Given  Data:

Time (T) = 2hrs 30mins 

where 2hrs =120mins

2hrs & 30mins = (120 + 30)mins = 150mins

150mins to Seconds = 150 x60 = 9,000s

Q = I x T

2 x 9,000 =18,000

where mg has valency of +2

So 2 x 96500 will discharge 24g of mg

and 18,000 will discharge xg of mg

2 x 96500 =24

18,000 =x

x = 24×18,0002x96500

≈ 2.00g

234.

The IUPAC nomenclature of the compound
H3C - CH(CH3) - CH(CH3) - CH2 - CH3

A.

3,4- dimethylhexane

B.

2,3- dimethyl pentane

C.

2- ethyl hexane

D.

2,3- dimethylhexane

Correct answer is B

No explanation has been provided for this answer.

235.

A compound contains 40.0% carbon, 6.7% hydrogen and 53.3% oxygen. If the molar mass of the compound is 180. Find the molecular formula.
[H = 1, C = 12, O = 16]

A.

C3H6O3

B.

C6H6O3

C.

C6H12O6

D.

CH2O

Correct answer is C

C → 40/12 ≈ 3

H → 6.7/1 ≈ 6

O → 53.3/16 ≈ 3

dividing through with the lowest value, 3

C1H2O1

[C1H2O1]n = 180

[12 + 2 + 16]m = 180

30n = 180 

n = 6

:C6H12O6