Gibbs Free Energy Video Lessons

Concept

# Problem: Consider the following reaction occurring at 298 K: N2O(g) + NO2(g) ⇌ 3 NO(g)​If a reaction mixture contains only N2O and NO2 at partial pressures of 1.0 atm each, the reaction will be spontaneous until some NO forms in the mixture. What maximum partial pressure of NO builds up before the reaction ceases to be spontaneous?​

###### FREE Expert Solution

$\mathbf{∆}\mathbf{G}\mathbf{=}\mathbf{∆}\mathbf{G}\mathbf{°}\mathbf{+}\mathbf{RTlnQ}$

ΔG < 0 or ΔG = (–); the reaction is spontaneous
• ΔG = 0; the reaction is at equilibrium
• ΔG > 0 or ΔG = (+); the reaction is non-spontaneous

• Q = K; the reaction is at equilibrium
Q < K; the reaction shifts in the forward direction to reach equilibrium (spontaneous in the forward direction)
• Q > K; the reaction shifts in the reverse direction to reach equilibrium

the reaction ceases to be spontaneous → when the reaction reached equilibrium

$\mathbf{0}\mathbf{=}\mathbf{∆}\mathbf{G}\mathbf{°}\mathbf{+}\mathbf{RTlnK}\phantom{\rule{0ex}{0ex}}\mathbf{∆}\mathbf{G}\mathbf{°}\mathbf{=}\mathbf{-}\mathbf{RTlnK}$

Step 1:

N2O(g) + NO2(g) ⇌ 3 NO(g)

ΔG° = 107.8 kJ

ΔG° = 107800 J

Step 2:

K = 1.2697x10-19

Step 3:

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###### Problem Details

Consider the following reaction occurring at 298 K: N2O(g) + NO2(g) ⇌ 3 NO(g)

If a reaction mixture contains only N2O and NO2 at partial pressures of 1.0 atm each, the reaction will be spontaneous until some NO forms in the mixture. What maximum partial pressure of NO builds up before the reaction ceases to be spontaneous?