Chemistry ideal gases

Structure 1.5.1: Ideal Gas Model

Structure 1.5.1: Ideal Gas Model

• Ideal gases consist of moving particles with negligible volume and no intermolecular forces.

• Collisions between particles are elastic.

Structure 1.5.2: Real Gases vs. Ideal Gases

• Real gases deviate from the ideal gas model at low temperatures and high pressures.

• Molar volume of an ideal gas is constant at specific temperature and pressure.

Structure 1.5.3: Ideal Gas Equation

• The relationship between pressure, volume, temperature, and the amount of an ideal gas is shown in the equation 𝑝𝑉=𝑛𝑅𝑇pV=nRT and the combined gas law 𝑝1𝑉1𝑇1=𝑝2𝑉2𝑇2T1​p1​V1​​=T2​p2​V2​​.

Assumptions of the Ideal Gas Model

• Constant Random Motion: Gas molecules move in straight lines until they collide.

• Elastic Collisions: No energy is lost in collisions.

• Negligible Volume: Volume occupied by gas molecules is insignificant compared to the container volume.

• No Intermolecular Forces: Ideal gases do not condense into liquids.

• Kinetic Energy and Temperature: Kinetic energy of molecules is proportional to Kelvin temperature.

Pressure-Volume Relationships (Boyle’s Law)

• Pressure is inversely proportional to volume at constant temperature.

• The SI unit of pressure is the pascal (Pa).

• Standard conditions for gases are 0°C (273.15K) and 100.0 kPa.

Real Gases vs. Ideal Gases

• Deviations at Low Temperature: Reduced kinetic energy causes intermolecular forces to form, making collisions inelastic.

• Deviations at High Pressure: The volume occupied by molecules becomes significant, affecting the inverse pressure-volume relationship.

Activities

• Assumptions and Conditions: Discuss conditions leading to deviations from ideal behavior.

• Comparisons: Predict which gases exhibit ideal behavior under different conditions.

Molar Volume of an Ideal Gas

• Avogadro’s Law: Equal volumes of gases at the same temperature and pressure contain equal numbers of particles.

• At STP, the molar volume of an ideal gas is 22.7 dm³ mol⁻¹.

Experimental Determination of Molar Mass

• Use the ideal gas equation to determine the molar mass of a gas.

• Conduct experiments with butane and analyze data to find molar mass.

• Consider sources of experimental error and improvements to methodology.

Ideal Gas Equation

Ideal Gas Equation

• The combined gas law 𝑝𝑉𝑇TpV​ remains constant.

• The ideal gas equation 𝑝𝑉=𝑛𝑅𝑇pV=nRT uses the gas constant 𝑅≈8.31R≈8.31 JK⁻¹mol⁻