Kinetic Theory & Gas

Assumptions of Kinetic Theory

The gas molecules are moving very fast and randomly; the molecules hardly have any volume; the gas molecules do not attract or repel each other (no intermolecular forces); no kinetic energy is lost when the gas molecules collide with each other (elastic collisions); the temperature of the gas is directly proportional to the average kinetic energy of the molecules.

Ideal Gas Molecules Volume

False. Ideal gas molecules are assumed to have negligible volume.

Elastic Collision

An elastic collision is when no kinetic energy is lost when gas molecules collide with each other.

Temperature and Kinetic Energy Relationship

The temperature of the gas is directly proportional to the average kinetic energy of the molecules, i.e. as temperature increases, the average kinetic energy increases.

Ideal Gas Definition

An ideal gas is a gas that follows the kinetic theory of gases.

Real Gases vs Ideal Gases

False. Real gases do not exactly fit the description of ideal gases but may come very close.

Factors Affecting Gas Volume

The volume that a gas occupies depends on its pressure and temperature.

Elastic vs Inelastic Collisions

In an elastic collision, energy is conserved and particles move away in opposite directions. In an inelastic collision, kinetic energy is not conserved and particles usually stick together.

Kinetic Theory Assumption on Attraction

False. The kinetic theory assumes gas molecules do not attract or repel each other (no intermolecular forces).

Gases and Pressure in Containers

Gases exert pressure as the gas molecules are constantly colliding with the walls of the container.

Boyle's Law

Boyle's Law states that pressure is inversely proportional to volume at constant temperature.

Mathematical Expression of Boyle's Law

The mathematical expression of Boyle's Law is P ∝ 1/V or PV = constant.

Effect of Decreasing Volume on Pressure

True. Decreasing the volume of a gas at constant temperature increases its pressure.

Charles' Law Definition

Charles' Law states that volume is directly proportional to temperature in Kelvin at constant pressure.

Mathematical Expression of Charles' Law

The mathematical expression of Charles' Law is V ∝ T or V/T = constant.

Effect of Increasing Temperature on Pressure

Increasing temperature at constant volume increases the pressure of the gas.

Pressure and Temperature Relationship

False. Pressure is directly proportional to temperature at constant volume.

Ideal Gas Equation

The ideal gas equation is PV = nRT.

P in Ideal Gas Equation

P represents pressure (in pascals, Pa) in the ideal gas equation.

V in Ideal Gas Equation

V represents volume (in m³) in the ideal gas equation.

n in Ideal Gas Equation

n represents the number of moles of gas (mol) in the ideal gas equation.

R in Ideal Gas Equation

R represents the gas constant (8.31 J K⁻¹ mol⁻¹) in the ideal gas equation.

T in Ideal Gas Equation

T represents temperature (in Kelvin, K) in the ideal gas equation.

Ideal Gas Equation and Molar Mass

True. The ideal gas equation can be used to calculate the molar mass of a gas.

Celsius to Kelvin Conversion

To convert temperature from Celsius to Kelvin, add 273 to the Celsius temperature.

Kilopascals to Pascals Conversion

To convert pressure from kilopascals to pascals, multiply by 1000.

dm³ to m³ Conversion

To convert volume from dm³ to m³, divide by 1000.

cm³ to m³ Conversion

To convert volume from cm³ to m³, divide by 1000000.

Pressure in Ideal Gas Equation

True. Pressure in the ideal gas equation should be in pascals (Pa).

Ideal Gas Equation Pressure

Pressure in the ideal gas equation should be in pascals (Pa).

Volume Calculation for Oxygen

Calculate the volume, in dm3, occupied by 0.5 mol of oxygen at a pressure of 220 kPa and a temperature of 21 °C. The volume is 5.55 dm3.

Pressure Calculation for Gas

Calculate the pressure of a gas, in kPa, given that 0.10 moles of the gas occupy 10.0 dm3 at a temperature of 25 oC. The pressure is 24.5 kPa.

Temperature Calculation for Gas

Calculate the temperature of a gas, in oC, if 0.05 moles of the gas occupy 1.0 dm3 at a pressure of 100 kPa. The temperature is -32.3 oC.

Molar Mass Calculation

A flask of volume 1000 cm3 contains 6.0 g of a gas. The pressure in the flask was 300 kPa and the temperature was 23 °C. The molar mass of the gas is 54.2 g mol-1.

Real Gases Deviation Conditions

Real gases show significant deviation from the ideal gas equation when the temperature is very low or the pressure is very high.

Kinetic Theory Assumption on Volume

The kinetic theory assumes that the volume the actual gas molecules themselves take up is tiny compared to the volume the gas occupies in a container.

Kinetic Theory Interaction Assumption

The kinetic theory assumes no interaction between gas molecules.

Intermolecular Forces Effect on Pressure

At high pressures, intermolecular forces cause attraction between molecules, reducing the number of collisions with the container walls and resulting in less pressure than expected by the ideal gas equation.

Fraction of Space at Low Temperatures and High Pressures

At low temperatures and high pressures, the fraction of space taken up by the molecules becomes substantial compared to the total volume.

Real Gases vs Ideal Gases

Real gases always behave exactly like ideal gases. False.

Deviation from Ideal Gas Behavior

Real gases deviate from ideal gas behavior, especially at low temperatures and high pressures.

Volume Impact on Ideal Gas Equation

The ideal gas equation becomes increasingly inaccurate at low temperatures and high pressures because the volume of gas molecules becomes significant compared to the total volume.

Pressure Reduction at High Pressures

At high pressures, intermolecular attractions reduce collisions with container walls, causing the pressure to be less than expected by the ideal gas equation.

Ideal Gas Equation Accuracy

The ideal gas equation is always accurate for all gases under all conditions. False.

Significant Deviations of Ideal Gas Equation

The ideal gas equation shows significant deviations for real gases, especially at low temperatures and high pressures.

Low Temperatures Effect on Real Gases

At low temperatures, real gases deviate significantly from ideal gas behavior because the gas molecules are closer together, making intermolecular forces more significant.