Diethyl ether (CH3CH2OCH2CH3) was one of the first chemicals used as an anesthetic.?

The vaporization of diethyl ether :
CH₃CH₂OCH₂CH₃(l) ⇌ CH₃CH₂OCH₂CH₃(g) …… Kp = P(CH₃CH₂OCH₂CH₃(g))
(This is a heterogeneous equilibrium. Only gases appear in the equilibrium expression.)

When T₁ = (273.2 + 34.6) K = 307.8 K, K₁ = 760 torr
When T₂ = (273.2 + 13.9) K = 287.1 K, K₂ = 343 torr

ln(K₁/K₂) = (ΔH/R) [(1/T₂) - (1/T₁)]

ΔH of vaporization for diethyl ether
= R ln(K₁/K₂) / [(1/T₂) - (1/T₁)]
= 8.314 × ln(760/343) / [(1/287.1) - (1/307.8)] J/mol
= 28200 J/mol
= 28.2 kJ/mol

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