Pressure, Dalton’s law, Vapor Pressure

Flashcards about Pressure and Gas Laws

What is vapor pressure?

Pressure from evaporation of gas above a liquid

How does temperature affect vapor pressure?

Higher temperature → higher vapor pressure

When does a liquid boil?

When vapor pressure = atmospheric pressure

How is vapor pressure handled when collecting gas over water?

Subtract water’s vapor pressure from total pressure:

What defines a volatile substance?

High vapor pressure (evaporates easily).

Where does evaporation occur?

Only at the liquid’s surface.

How does evaporation affect liquid temperature?

Lowers temperature (fastest particles escape).

What condition defines boiling equilibrium?

• Equilibrium Condition:
  Vapor pressure = external pressure (e.g., atmospheric).

  X(l)⇌X(g)

• Key Features:

  • Occurs throughout the liquid (not just surface).

  • Temperature stays constant during boiling (latent heat).

  • Lower external pressure → lower boiling point.

• vs. Evaporation:
  Boiling requires fixed T/PT/P; evaporation happens at any TT on the surface.

What causes gas pressure?

Collisions between gas particles and container walls.

How does particle count affect pressure (fixed T/V)?

Doubling particles doubles pressure; halving particles halves pressure.

State Dalton’s Law of Partial Pressures.

Total pressure = sum of partial pressures of individual gases:
Ptotal=P1+P2+P3+⋯Ptotal​=P1​+P2​+P3​+⋯

How is partial pressure calculated using mole fraction?

P_total = % occurance P_total + % occurance P_total…