Lecture Notes: Ideal Gas Law

Introduction

• Topic: Ideal Gas Law
• Presented by: Andre from Med School EU
• Relevance: Part of the composition of matter unit

Ideal Gas Assumptions

• Characteristics:
  • Ideal gases have zero particle volume
  • No intermolecular forces of attraction
• Reasoning:
  • Particle volume and intermolecular forces are negligible
  • Assumed for equation accuracy

Dependence of Volume

• Factors:
  • Temperature (Kelvin)
  • Pressure (Pascals or Kilopascals)
• Pressure Source:
  • Gas molecules colliding with walls and each other
  • Inverse relationship with volume

Ideal Gas Formula

• Equation: PV = nRT
  • P = Pressure (atm or kPa)
  • V = Volume (liters)
  • n = Number of moles
  • R = Ideal gas constant (0.0821 L atm / K mol)
  • T = Temperature (Kelvin)
• Conversions:
  • Celsius to Kelvin: Add 273
  • 1 atm = 101.3 kPa

Standard Temperature and Pressure (STP)

• Definition:
  • Standard Temperature: 0°C or 273K
  • Standard Pressure: 1 atm or 101.3 kPa
• Usage:
  • 1 mole of an ideal gas = 22.4 liters at STP
  • Useful for conversions in volume and moles

Example Problem 1

• Scenario:
  • Exhaling 125 mL CO₂ at 37°C and 0.95 atm
  • Find volume at 10°C and 0.9 atm
• Steps:
  1. Convert 37°C to 310K
  2. Use PV = nRT to find moles
  3. Rearrange to find new volume V = nRT/P
  4. Answer: 0.12 liters

Example Problem 2: Stoichiometry

• Question:
  • Volume of 10g methane gas at STP
• Process:
  1. Convert 10g of CH₄ to moles
  2. Use molar mass (CH₄ = 16.043 g/mol)
  3. Convert moles to volume using 1 mole = 22.4 liters
  4. Answer: 13.96 liters of CH₄ gas

Conclusion

• This lecture covered the ideal gas law and included example calculations related to PV=nRT, stoichiometry, and conversions.
• Next topic: Atomic structure and atomic theory.