Question

1. A 5 cm3 balloon is filled by a gas at a pressure

of 1 x 105 Pa . When the balloon is filled by 20

cm3 of the gas, what is the new pressure of the

gas?



A 1.0 x 105 Pa B 4.0 x 104Pa

C 2.5 x 104Pa D 4 x 103 Pa

E 5x 103 Pa


2. A bubble of air is formed at the base of a lake.

At that moment, its volume is 30 cm3 and it

experiences a pressure of 190 of cm Hg. What

is the volume of the bubble when it reaches the

surface of the sea.

[ The atmospheric pressure =

76 cm of Hg ]

A 25 cm3 B 50 cm3

C 75 cm3 D 100 cm3

E 150 cm3

​

Answer 1

1) C. 2.5 x 10⁴ Pa

2) C. 75 cm³

Step-by-step explanation:

Question 1.

Given the following data;

• Initial volume, V1 = 5 cm³
• Initial pressure, P1 = 1 * 10⁵ Pa
• Final volume, V2 = 20 cm³

To find the final pressure, P2, we would use Boyle's law;

Boyles states that when the temperature of an ideal gas is kept constant, the pressure of the gas is inversely proportional to the volume occupied by the gas.

Mathematically, Boyles law is given by;

PV = K

P1V1 = P2V2

Making P2 the subject of formula, we have;

P2 = (P1V1)/V2

Substituting into the formula, we have;

P2 = (1 * 10⁵ * 5)/20

P2 = (500,000)/20

Final pressure, P2 = 25,000 Pa or 2.5 x 10⁴ Pa.

Question 2.

Given the following data;

• Initial volume, V1 = 30 cm³
• Initial pressure, P1 = 190 of cm Hg
• Final pressure, P2 = 76 cm of Hg

To find the final volume, we would use Boyle's law;

Mathematically, Boyles law is given by;

PV = K

P1V1 = P2V2

Making V2 the subject of formula, we have;

V2 = (P1V1)/P2

Substituting into the formula, we have;

V2 = (190 * 30)/76

V2 = 5700/76

Final volume, V2 = 75 cm³