Gases

Question 1

Describe standard conditions [STP]

Answer 1

Standard temperature (0℃) and pressure (100 kPa)

Question 2

Recall how molar volume of gas (at certain conditions) is calculated

Answer 2

= [molar mass]/density (at same certain conditions)

Question 3

Recall the molar volume of any gas at STP

Answer 3

22.7 dm³mol⁻¹

Question 4

Recall how number of moles of a gas at STP is calculated

Answer 4

= [volume of gas (dm³)]/[molar volume]
= [volume of gas (dm³)]/[22.7 dm³mol⁻¹]

Question 5

Describe the kinetic theory of gases

Answer 5

The particles in a gas are in continual, rapid, random motion in straight lines in every direction

• The pressure exerted by a gas on the walls of its container is due to bombardment by the moving particles
• The particles in a gas are separated from each other by distances that are large as compared with the size of the particles
• The particles are regarded as being perfectly elastic so that the collisions they undergo in a gas do not result in any change in the total amount of kinetic energy of the gas
• An increase in temperature causes the motion and hence kinetic energy of the particles to increase

Question 6

Describe the quantitative relationship between pressure, temp and volume

Answer 6

The volume of a given gas sample is directly proportional to its absolute temperature at constant pressure

The volume of a given amount of gas is inversely proportional to its pressure when temperature is held constant

Question 7

Recall Boyle’s law

Answer 7

At constant temperature, the volume of a given mass of a gas is inversely proportional to the pressure exerted on it

Question 8

Recall Charles’s law

Answer 8

At a constant pressure, the volume of a given mass of a gas is directly proportional to the absolute temperature

Question 9

Recall Gay-Lussac’s law

Answer 9

The pressure of a gas of fixed mass and fixed volume is directly proportional to the gas’s absolute temperature

Question 10

Recall Avogadro’s law

Answer 10

1 mole of gases should have the same volume at the same temperature and pressure

Question 11

Define inversely proportional

Answer 11

When the value of one quantity increases with respect to decrease in other or vice-versa

Question 12

Define directly proportional

Answer 12

As one quantity increases, the other increases at the same rate

Question 13

Recall the ideal gas equation

Answer 13

PV=nRT

• P - Pressure (Pa [pascals])
• V - Volume (m³)
• n - Number of Moles (mol)
• R - Constant (8.31 [in an ideal gas])
• T - Temperature (K)