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Chemistry questions and answers

Chemistry Questions and Answers

Learn more about the properties, composition, and structure of substances (elements and compounds) with these Chemistry questions and answers. This Test can be used by students preparing for Chemistry in JAMB, WAEC, NECO or Post UTME.

466.

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

467.

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.

468.

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

469.

In the reaction:
M + N → P
ΔH = +Q kJ

Which of the following would increase the concentration of the product?

A.

Adding a suitable catalyst

B.

Increasing the concentration of P

C.

Increasing the temperature

D.

Decreasing the temperature

Correct answer is C

No explanation has been provided for this answer.

470.

Sulphur exists in six forms in the solid state. This property is known as

A.

Isomerism

B.

Allotropy

C.

Isotopy

D.

Isomorphism

Correct answer is B

No explanation has been provided for this answer.