Chemistry - Module 4

Kinetic Theory of Gases

• Gases consist of tiny particles in constant, rapid, random motion.

• Collisions between particles and container walls create pressure.

• Collisions are elastic with negligible attractive/repulsive forces between particles.

• The average kinetic energy of gas particles is proportional to their temperature in Kelvin.

Gas Measurements

• Key properties include temperature (measured in Celsius and Kelvin), pressure (measured in pascals, mmHg, and atmospheres), and volume (liters or cubic meters).

• Standard temperature and pressure (STP): 0°C (273 K) and 101.3 kPa.

Gas Laws

Boyle’s Law

• As pressure increases, volume decreases at constant temperature: ( P1 V1 = P2 V2 )

• Related examples such as the Felix Baumgartner space jump to illustrate low pressure at altitude.

Charles’ Law

• Describes the relationship between temperature and gas volume; volume increases with temperature at constant pressure: ( V1/T1 = V2/T2 )

Combined Gas Law

• Combining the principles of Boyle’s and Charles’s Laws to relate pressure, volume, and temperature: ( P1 V1/T1 = P2 V2/T2 )

• Example problems calculating changes in gas volumes with altitude.

Avogadro’s Hypothesis

• Equal volumes of gases at the same temperature and pressure contain equal numbers of molecules.

• Molar volume of an ideal gas at STP is 22.4 L.

• Practical examples demonstrate how to calculate gas volumes from moles and conditions.

Dalton’s Law of Partial Pressures

• The total pressure in a mixture of non-reacting gases equals the sum of partial pressures of individual gases: ( P = P1 + P2 + … )

Important Gases and Their Laboratory Preparations

• Hydrogen: Produced by reacting zinc with hydrochloric acid

• Oxygen: Decomposed from hydrogen peroxide

• Carbon Dioxide: Generated from calcium carbonate reacting with hydrochloric acid

Atmospheric Composition and Issues

• Composition of unpolluted dry air: approximately 78.1% nitrogen, 20.9% oxygen, and trace gases.

• Addressing climate change via innovations like carbon capture technologies.

• Discussing issues such as ozone depletion (caused by CFCs), photochemical smog, acid rain, and the greenhouse effect, which are essential for understanding environmental challenges.

Conclusion

• A holistic understanding of gas behaviors, measurements, and their implications is crucial in both chemistry and environmental science.