Chapter 15: Ideal Gases

Question 1

What is a mole of substance?

Answer 1

A mole of substance is defined as 6.02x10^23 individual atoms or molecules of that substance.

Question 2

What is the kinetic theory of gases?

Answer 2

The Kinetic Theory of Matter is a model used to describe the behaviour of atoms or molecules in an ideal gas. These come up with the conclusions:

• Gases contain a large number of atoms or molecules that move in random directions in random speeds.
• The atoms or molecules in a gas occupy a negligible volume compared to the volume of the gas.
• Collisions of atoms or molecules between atoms/molecules or containers are perfectly elastic (no kinetic energy is lost).
• The time of collisions between atoms or molecules are negligible compared to the time between collisions
• Electrostatic Forces between atoms or molecules in a gas are negligible except during collisions.

Question 3

How is Pressure linked to Volume?

Answer 3

Pressure is inversely proportional to the volume of the container given that temperature remains constant.

Question 4

How is Pressure linked to Temperature?

Answer 4

Pressure is directly proportional to temperature given that that the mass and volume remain constant. Also known as Charles’ Law.

Question 5

What is the combined equation of Gas Laws?

Answer 5

The combined equation of Gas Laws is: pV / T = Constant

Question 6

What is the gas law equation before and after a reation?

Answer 6

The gas law equation before and after a reaction is:

pV / T (before) = pV / T (after)

Question 7

What is the equation for an ideal gas?

Answer 7

The equation for an ideal gas is: pV = nRT

where ‘n’ is the number of moles, and ‘R’ is the Molar Gas Constant

Question 8

What is the gradient and equation of a pV - nRT Graph?

Answer 8

The gradient of a pV - nRT Graph is nR, and the equation is:
pV = nRT
y = m x

Question 9

What is Root Mean Square Speed?

Answer 9

Root Mean Square Speed is found by squaring the speeds of all atoms, finding their mean/average and square rooting it.

Question 10

What is the equation for Pressure at the microscopic level?

Answer 10

The equation for pressure at the Microscopic Level is:

pV = 1/3 Nmc^2_ (where c^2_ is the mean square speed, and N is the Number of Particles)

Question 11

What is the Maxwell-Boltzmann Distribution?

Answer 11

The Maxwell-Boltzmann Distribution is a Graph that shows the number of particles to the speed of the particles at a given temperature. At higher temperatures, the graph is flatter and more spread out.

Question 12

What is the Boltzmann Constant, and how is it found?

Answer 12

The Boltzmann Constant is defined as the mean kinetic energy of atoms or molecules within a gas at room temperature.
The Boltzmann Constant is calculated by dividing the Molar Gas Constant by Avogadro’s Constant, and has the symbol ‘k’.
k = R / (N a)

Question 13

What is the equation for ideal gas at the molecular level?

Answer 13

At the molecular level, the equation for an ideal gas is: pV = NkT

Question 14

What is the equation that links mean kinetic energy and temperature?

Answer 14

The equation that links mean kinetic energy and temperature is:
1/3 NmC^2_ = NkT
1/3 m c^2_ = kT
2/3 x (1/2 mc^2) = kT (factoring out 2/3 from left side)
1/2 mc^2 = 3/2 kT

Therefore Kinetic Energy is directly proportional to temperature.