Chapter 15 - Ideal Gases

Question 1

What is the Avogadro’s Constant?

Answer 1

Question 2

What is the formula for finding the number of atoms in a substance?

Answer 2

Question 3

State the kinetic theory of gases.

Answer 3

The Kinetic Theory of Gases makes certain assumptions, for the simplicity of calculations:

• The gas contains a very large number of atoms or molecules moving in random directions with random speeds.
• The atoms or molecules of the gas occupy a negligible volume compared with the volume of the gas.
• The collisions of atoms or molecules with each other and the container walls are perfectly elastic (no kinetic energy is lost).
• The time of collisions between the atoms or molecules is negligible compared to the time between the collisions.

Question 4

Define the mass of an object using Moles.

Answer 4

The mass of the object is defined as:

m = n x M
Mass = number of moles x Molar Mass.
kg = (number) x (molar mass)

Question 5

Define Boyle’s Law.

Answer 5

Boyle’s Law states that pressure is inversely proportional to its volume. This was investigated and proven by Robert Boyle in 1662, using a sealed tube and pressurised gas. The gradient is the gas constant.

Question 6

What is the equation of state of an ideal gas?

Answer 6

The equation of state of an ideal gas is defined as:

pV = nRT
pressure x Volume = moles x Molar Gas Constant x Temperature.

Question 7

Define the RMS speed of particles in a gas?

Answer 7

In order to determine the r.m.s speed, you apply the following equation.

√(mean of c)² = c (r.m.s)

RMS stands for root mean squared.

Question 8

Define the Boltzmann Constant, k.

Answer 8

The Boltzmann Constant is equal to the molar gas constant divided by the Avogadro constant.

k = R ÷Nₐ = 1.38 x 10⁻²³

Question 9

How is gas temperature handled in ideal gas physics?

Answer 9

Gas temperatures are always recorded in kelvin.

Question 10

What are the effects of doubling the temperature of an ideal gas for internal energy?

Answer 10

Doubling the temperature of an ideal gas doubles the kinetic energy of the gas and therefore, doubles its internal energy.

Question 11

What is the second equation of state of an ideal gas?

Answer 11

The second equation of state of an ideal gas is:

pV = nkNₐT
pressure x Volume = number of moles x Boltzmann Constant x Avogadro’s constant x Temperature

Question 12

How to find the number of particles in the gas sample?

Answer 12

To find the number of particles in the gas sample:

pV = NkT
pressure x Volume = Number of Particles x Boltzmann Constant x Temperature.

Question 13

What is the relationship between Mean Kinetic Energy and Temperature?

Answer 13

Mean Kinetic Energy and Temperature are mutually connected by pressure x volume, and are equivalent via the following expressions:

1/3 Nm c²(r.m.s) = NkT.
or
1/2 mc²(r.m.s) = 3/2 kT.

Question 14

Define Charles’ Law.

Answer 14

Charles’ Law states that the volume of an ideal gas at constant pressure is directly proportional to the absolute temperature.

Question 15

Define pressure and volume im microscopic terms?

Answer 15

Pressure and Volume can be expressed as:

pV = ⅓Nm c² (r.m.s)
pressure x Volume = 1/3 x Number of particles x mass x r.m.s speed squared