Gaseous State

Question 1

What is the Standard Temperature and Pressure? (Stp)

Answer 1

Temperature = 0°C =273K
Pressure = 1 bar = 1.00 x 10^5 Pa

Question 2

What is the Room Temperature and Pressure?

Answer 2

Temperature = 20°C = 293K
Pressure = 1 atm = 101325 Pa

Question 3

What is Avogadro’s law?

Answer 3

Avogadro’s law states that equal volumes of all gasses under the same conditions of temperature and pressure contains the same number of particles.

1. Volume of a gas at constant temperature and pressure is directly proportional to the number of moles of the gas
V = kn                V ∝ n
V = volume      K = proportionality constant       N = mole

2. Volume ( molar volume )occupied by one mole of any gas at the same temperature and pressure must be the same. 
At S.t.p. ( 1 bar, 273K), molar volume =22.7dm^3
At r.p.t. ( 1 atm, 293K), molar volume = 24.0dm^3

3. Ratio between the number of moles of gases is equal to the ratio between their volumes
Mole ratio = volume ratio V1/V2=n1/n2

Question 4

What is Boyle’s law?

Answer 4

Boyle’s law
Boyle’s law states that the pressure of a fixed mass of a gas is inversely proportional to its volume at constant temperature

P ∝ 1/v pV=k p1V1=p2V2

Question 5

What is Charles’ law?

Answer 5

Charles’ law states that the volume of a fixed mass of gas is directly proportional to its absolute temperature (K) at constant pressure

V ∝ T V=kT V1/T1=V2/T2

The volume of any gas is zero at 0K or 273°C
The temperature reflects a complete lack of energy and is called the absolute zero

Question 6

What is combined gas law?

Answer 6

Combining Boyle’s law and Charles’ law
Boyle’s law: p ∝ 1/v
Charles’ law: V ∝ T
V ∝ T/p P1V1/T1=p2V2/T2

Question 7

What is Dalton’s law of partial pressure?

Answer 7

Dalton’s law of partial pressure
Dalton’s law states that in a mixture of gases that do not react chemically, the total pressure of the mixture is equals to the sum of the partial pressure exerted by the constituent gases.
Pt = Pa + Pb Assuming that volume of gas a and b is the same
Pa =na/nt x pt Na/nt=mole fraction of A

Question 8

What are the assumptions for ideal gas behaviour?

Answer 8

Assumptions for ideal gas behaviour

1) The intermolecular forces of attraction between gas particles are negligible
2) The total volume of gas particles is negligible compared to the volume of the container
3) Gas particles in continuous random linear motion.
4) All collisions between gas particles are perfectly elastic so that no kinetic energy is lost on collision.

Question 9

When do real gas tends towards ideal gas behaviour?

Answer 9

1) Pressure is very low

At very low pressure, real gases behave close to ideal because the gas particles are far apart and the volume of the gas particles is less significant compared to the volume of the container. There is less significant intermolecular forces of attraction between the particles.

2) Temperature is very high

At high temperature, real gases behave close to the ideal because the gas particles have very high kinetic energies and hence intermolecular forces of attraction between particles are easily overcome, becoming less significant.