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.

871.

Calculate the volume in cm3 of oxygen evolved at s.t.p when a current of 5A is passed through acidified water for 193s?
[F = 96500 C mol1. Molar volume of a gas at s.t.p = 22.4dm3]

A.

0.056dm3

B.

0.224dm3

C.

224.000dm3

D.

56.000dm3

Correct answer is A

Q = 193 x 5 = 965C
40H \(\mapsto\) 2H2O + O2 + 4e
4 x 96500C = 22.4dm3
965C = x

x = \(\frac{22.4 \times 965}{4 \times 96500}\)
= 0.056dm3

872.

An isotope has an atomic number of 15 and a mass number of 31. The number of proton it contains is

A.

16

B.

15

C.

31

D.

46

Correct answer is B

No explanation has been provided for this answer.

873.

An example of a solid emulsion is

A.

Butter

B.

Hair cream

C.

Milk

D.

Cod-liver oil

Correct answer is A

No explanation has been provided for this answer.

874.

In a neutralization reaction involving HCI and NaOH using litmus as indicator, the colour at the end point is

A.

Blue

B.

Red

C.

Orange

D.

Purple

Correct answer is D

Neutral litmus paper is purple.  the result of a neutralization reaction is salt and water and hence is neutral.

875.

In the extraction of iron, the waste gas from the furnace is a mixture of

A.

PH3 CO and CO2

B.

CO and C

C.

N2 , CO and CO2

D.

PH3 and CO

Correct answer is C

the \(N_2\) from the hot air blast to burn the coke (48%), the \(CO\) (23%) and \(CO_2\) (21%) produced from the reduction of the iron ore \(Fe_{2}O_{3}\) by carbon (the coke) are the major components of the waste from the extraction.