Question 1

What is vapor pressure?

Accepted Answer

Vapor pressure is the pressure exerted by a vapor in equilibrium with its liquid (or solid) at a given temperature. When vapor pressure equals atmospheric pressure, the liquid boils.

Question 2

What is the Clausius-Clapeyron equation?

Accepted Answer

The Clausius-Clapeyron equation relates vapor pressure to temperature: ln(P₂/P₁) = -(ΔH_vap/R)(1/T₂ - 1/T₁). It uses a known vapor pressure at one temperature to calculate at another.

Question 3

What is the Antoine equation?

Accepted Answer

The Antoine equation is an empirical formula: log₁₀(P) = A - B/(C+T). A, B, and C are substance-specific constants determined experimentally. It is more accurate than the Clausius-Clapeyron equation over wider temperature ranges.

Question 4

Why does boiling point change with altitude?

Accepted Answer

At higher altitudes, atmospheric pressure is lower. Since a liquid boils when its vapor pressure equals atmospheric pressure, it boils at a lower temperature at higher altitudes. This is why water boils below 100°C on mountains.

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