The effect of temperature on balance

Subtract the two types and arrange them to get

or

Two or more temperature T is given by the standard equilibrium constant K ^[Theta] effects, i.

(1) For the endothermic reaction △rHm ^Θ > 0, when the temperature is increased (T2> T1), K2 ^Θ > K1 ^Θ
.

(2) For the exothermic reaction △rHm ^Θ <0, when the temperature is increased (T2>T1), K2 ^Θ > K1 ^Θ
.

Through the standard equilibrium constants K1 ^Θ and K2 ^{Θ at} two different temperatures T1 and T2, the thermal effect △rHm ^{Θ of} the reaction can be obtained
.

[Example 4-6] When the synthetic ammonia is reacted at 473K, K ^Θ = 0.

Solution (1) Substitute the K ^Θ values at 473K and 873K into the formula

(2) Substitute the melting change of the reaction and the K ^Θ value at 473K into the formula

Equilibrium constant at 673K

K2 ^Θ =2.

Gasification process of liquid substance B

The standard equilibrium constant K ^Θ is

In the formula, pB* is the saturated vapor pressure of B; p ^Θ is the standard atmospheric pressure
.

The saturated vapor pressures of B at different temperatures T1 and T2 are p1* and p2* respectively, and the standard equilibrium constants of the gasification reaction of B at different temperatures T1 and T2 are respectively

Substitution

Get

This formula is the quantitative relationship between saturated vapor pressure and temperature of liquid substances
.