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.

151.

If 50 cm\(^{3}\) of a saturated solution of KNO\(_{3}\) at 40 °C contained 5.05 g of the salt, its solubility at the same temperature would be
[KNO\(_{3}\) = 101]

A.

1.0 mol dm\(^{-3}\)

B.

1.5 mol dm\(^{-3}\)

C.

2.0 mol dm\(^{-3}\)

D.

5.0 mol dm\(^{-3}\)

Correct answer is A

V= 50cm\(^{3}\)
Mass= 5.05g
Relative molecular mass of KNO\(_{3}\) = (39+14+(3*16)) = 101
Convert 50cm\(^{3}\) to dm\(^{3}\) which is
1000cm³ = 1dm\(^{3}\)
50cm³ = 50*1/1000
= 0.05dm\(^{3}\)
Moles = mass/ molar mass
= 5.05/101 =0.05mole
Solubility= mole/volume
Solubility=0.05mol/0.05dm\(^{3}\)
Solubility=1.0mol/dm_\(^{3}\)

152.

What number of moles of oxygen would exert a pressure of 10 atm at 320 K in an 8.2 dm\(^{3}\) cylinder?
[R=0.082 atm dm\(^{-3}\) mol\(^{-1}\) K\(^{-1}\)]

A.

0.32

B.

1.52

C.

3.13

D.

31.25

Correct answer is C

P = 10atm, T= 320K, V= 8.2dm\(^{3}\)
PV =nRT
n = P * V/R * T
10 * 8.2/0.082 * 320
= 82/26.24
n = 3.13

153.

A hydrogen chloride gas reacted with oxygen gas to yield water and chlorine gas. The mole ratio of the hydrogen chloride gas to water is

A.

1:3

B.

2:1

C.

3:1

D.

4:1

Correct answer is B

4HCl + O\(_{2}\) -- 2Cl\(_{2}\) + 2H\(_{2}\)O
4:2 = 4/2
2:1

154.

Which of the following statements about liquids is/are true?


I. Liquids maintain their volume at constant temperature.
II. Liquids have fixed shape
III. Liquids do not diffuse
IV. Change in pressure affects volume of liquids

A.

I only

B.

IV only

C.

I and IV only

D.

II and III only

Correct answer is A

A liquid is a nearly incompressible fluid that conforms to the shape of its container but retains a (nearly) constant volume independent of pressure

155.

When air in a syringe is compressed such that there is no change in temperature, the

A.

air liquefies

B.

pressure increases

C.

intermolecular space increases

D.

density decreases

Correct answer is B

Since the temperature of air remain constant.So, it is a isothermal process.
PV=K
This eq. shows that on increasing pressure, the volume gets reduced and vice-versa.
Since the syringe is slowly compressed, volume is decreasing.
Therefore, the pressure inside the syringe will increases because the molecules now hit the syringe walls more frequently.