NH4NO3(s) → N2O(g) + 2H2O(g) 25°C ΔG° Kp 30 atm (a)

NH4NO3(s) → N2O(g) + 2H2O(g) 25°C ΔG° Kp 30 atm (a)

 

 

Ammonium nitrate is dangerous because it decomposes

(sometimes explosively) when heated:

NH4NO3(s) → N2O(g) + 2H2O(g)

 

Given the following data

ΔH°_f [NH4NO3(s)] = -365.6 kJ/mol

ΔH°_f [N2O(g)] = 82.0 kJ/mol

ΔH°_f [H2O(g)] = -241.8 kJ/mol

S° [NH4NO3(s)] = 151.1 J/K•mol

S° [N2O(g)] = 219.7 J/K•mol

S° [H2O(g)] = 188.7 J/K•mol

 

a) Show that this reaction is spontaneous at 25 °C.

b) How does ΔG° for the reaction change when the temperature is raised?

c) Calculate the equilibrium constant Kp at 25 °C.

d) Calculate ΔG for the reaction when the partial pressure of each gas is 30 atm.

 

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a) Show that this reaction is spontaneous at 25 °C.

 

ΔH° = [생성물들의 ΔH°_f 합] – [반응물들의 ΔH°_f 합]

( 참고 https://ywpop.tistory.com/3431 )

 

= [(82.0) + 2(-241.8)] - [(-365.6)]

= -36.0 kJ

 

 

 

ΔS° = [생성물의 ΔS°의 합] - [반응물의 ΔS°의 합]

( 참고 https://ywpop.tistory.com/7404 )

 

= [(219.7) + 2(188.7)] - [(151.1)]

= +446.0 J/K

= +0.446 kJ/K

 

 

 

ΔG° = ΔH° - TΔS°

( 참고 https://ywpop.tistory.com/7438 )

 

= (-36.0 kJ) - (273+25 K) (+0.446 kJ/K)

= –168.9 kJ

 

 

 

ΔG° < 0 이므로,

이 반응은 25℃에서 자발적이다.

 

 

 

 

자발적 반응 예측. 여기에 반응식을 쓰시오.hwp

 

 

 

[키워드] 자발적 반응 예측 기준문서, ΔG = ΔH - TΔS 기준문서, ΔG° = ΔH° - TΔS° 기준문서