Gas Phase

Question 1

Pressure Conversions and STP

Answer 1

• 1 atm = 760 mmHg = 760 torr = 101.3 kPa.

* STP: 0°C (273K) and 1atm.

Question 2

Ideal Gas Law

Answer 2

• Ideal Gas has no intermolecular forces and occupies no volume.
• Ideal Gas Law: PV = nRT.
• Combined Gas Law: P₁V₁/T₁ = P₂V₂/T₂.
• Density: ρ = m/V = PM/RT, where density is mass per unit volume and M is molar mass of gas.
• Molar Mass: M = mRT/PV.

Question 3

Dalton’s Law of Partial Pressures

Answer 3

• Total pressure of a gaseous mixture is equal to the sum of the partial pressures of the individual components.
• Dalton’s Law: Pᴛ = Pᴀ + Pʙ + Pᴄ.
• Pᴀ = Xᴀ Pᴛ.
• Xᴀ = mol of gas A / total moles of gas.

Question 4

Henry’s Law of Vapor Pressure

Answer 4

• Vapor Pressure: Pressure exerted by evaporated particles above the surface of a liquid which forces some of the gas back into the liquid phase.
• [A]₁/P₁ = [A]₂/P₂, where P is partial pressure of gas A.

Question 5

Kinetic Molecular Theory

Answer 5

• The higher the temperature, the faster the molecules move.
• The larger the molecules, the slower they move.
• Graham’s Law of Diffusion and Effusion: r₁ / r₂ = sqrt(M₂ / M₁).
• Gas with M four times greater than M of another gas will diffuse half as fast.