Chemistry Questions & Answers - Free Online Practice

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]

1.0 mol dm $^{-3}$

1.5 mol dm $^{-3}$

2.0 mol dm $^{-3}$

5.0 mol dm $^{-3}$

View answer & explanation

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 $^{-1}$ ]

0.32

1.52

3.13

31.25

View answer & explanation

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

1:3

2:1

3:1

4:1

View answer & explanation

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

I only

IV only

I and IV only

II and III only

View answer & explanation

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

air liquefies

pressure increases

intermolecular space increases

density decreases

View answer & explanation

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.