Gas laws

Question 1

Boyle’s Law

Answer 1

• volume and pressure are inversely proportional if the temperature of a gas is kept constant
• volume is on the y-axis, pressure is on the x-axis
• P₁ V₁= P₂ V₂ (where P1 and V1 are the initial pressure and volume values, and P2 and V2 are the values of the pressure and volume of the gas after change)
• a reduction in the volume of a gas results in more particles per unit volume, therefore particles collide more frequently with the walls of the container
• hence pressure increases, since pressure is the rate of collision of particles with the walls of the container

Question 2

Charle’s Law

Answer 2

• volume and temperature are directly proportional if they are at a constant pressure
• volume is on the y-axis
• V₁ / T₁ = V₂ / T₂ (where V₁ and T₁ are initial volume and temperature, respectively. Similarly, V₂ and T₂ are the final values of these gas parameter)
• if the temperature is increased, the average kinetic energy of particles increase, therefore they collide with a greater force and frequency due to their increased velocity, hence pressure increases as the rate of particle collisions with the walls increases
• hence in order to maintain a constant pressure the collision of particles needs to be reduced which occurs by increasing volume as that decreases the number of particles per unit volume, therefore balancing the effect of the increase in kinetic energy to obtain a constant pressure

Question 3

Gay Lussac’s Law

Answer 3

• pressure and temperature are directly proportional, if volume is kept constant
• volume is on the y-axis
• P₁ / T₁ = P₂ / T₂ (where P₁ and T₁ are initial pressure and volume, respectively. Similarly, P₂ and T₂ are the final values of these gas parameter)
• when the temperature is increased the kinetic energy of particles increases, hence they move with a greater velocity which results in more frequent and forceful collisions with the container walls
• hence pressure increases as pressure is related to the rate of collision of particles with the walls of the container

Question 4

Combined Gas Law

Answer 4

• P₁ V ₁ / T₁ = P₂ V₂ / T₂

- combines Boyle’s Law ( P₁ V ₁ = P₂ V₂ ), Charle’s Law ( V ₁ / T₁ = V₂ / T₂ ), Gay Lussac’s Law ( P ₁ / T₁ = P₂ / T₂)

Question 5

Avogadro’s Hypothesis

Answer 5

• n = V / 22.71 (only works for gases at STP)
• equal volumes of gases, measured at the same temperature and pressure contain equal number of particles (and hence moles)
• if temperature and volume are the same and there is an equal number of particles of a gas, all gases will exert equal pressures

Question 6

Ideal Gas Law

Answer 6

• combination of all the molar volume relationship and combined gas law
• PV = nRT
• P = pressure in kPa
• T = temperature is in kelvins (0 K = -273.15 C)
• R = the universal gas constant 8.314
• V = volume in L
• n = number of moles
• the density of a gas depends on its volume, therefore pressure and temperature) and molar mass - it describes the ratio of mass to volume (density = m / V )

Question 7

Molar Volume

Answer 7

• one mole (6.022 x 10^23) of any gas will occupy the same volume under the same conditions of temperature and pressure
• the molar volume (volume of one mole) of any gas at STP is 22.71
• n = V / 22.71
• room temperature molar volume equals approximately 24.0L

Question 8

Standard Temperature and Pressure

Answer 8

• STP stands for standard temperature and pressure
• standard temperature is 273.15K (O C)
• standard pressure is 100 kPa (1 atm)

Question 9

Gas Pressure

Answer 9

• gas pressure is related to the collision of gas particles with the walls of the container
• gas pressure is determined by: particle momentum and frequency of collisions of the gas particles with the walls of the container
• units used for pressure is kPa
• 1 atmospheric pressure (atm) = 100kPa
• standard pressure is 100kPa
• force per unit area

Question 10

Temperature

Answer 10

• standard unit of temperature is kelvin
• 0 K = - 273.15 C
• 0 C = 273.15 K
• temperature is the average kinetic energy of all the particles
• kelvin is the temperature at which a gas occupies a volume of zero
• a rise in temperature means an increase in the average kinetic energy of gas particles, hence particles move with greater velocity hitting harder and bombarding the walls of the container more frequently, thus increasing the pressure