1. Consider the oxidation of methanol, CH3OH(g) +3/2(O2)(g) = CO2(g) + 2H2O(l) A
ID: 898437 • Letter: 1
Question
1. Consider the oxidation of methanol,
CH3OH(g) +3/2(O2)(g) = CO2(g) + 2H2O(l)
At T 25 degrees Celcius
Delta H formation (CO2,g)= -393.51 kj/mol
Delta H formation ( H2O,l)= -285.85 kj/mol
Delta H formation ( CH3,OH,g)= -200.66 kj/mol
Standard Entropy S(CO2, g)= 213.74 j/K*mol
Standard Entropy S(H20, l)= 69.91 J/K *mol
Standard Entropy S(CH3OH, g)= 239.81 J/k*mol
Standard Entropy S(O2, g)= 205.14 J/K*mol
a) Using the provided information calculate delta H formation at 25 degree celcius
b) Using the provided information calculate delta S reactant at 25 degree celcius
c) Calculate the total change in entropy (system and surroundings.)
d) Calculate Delta G formation at 25 degree celcius
e) Evaluate the equilibrium constant at 25 degree celcius
Explanation / Answer
a) dH = Hproduct - Hreactant
dH = (-393.51 + -285.85*2) - (-200.66 + 0) = -764.55 kJ/mol
b) dS = Sproduct - Sreact
dS = (213.74 + 2*69.91)-(239.81+3/2*205.14)= -193.96 J/Kmol
c)
Suniverse = Ssurrounding + Ssystem
S system = dS and Ssurrounding = Q/T
Since Q = dH then Ssurr = dH/T = -764.55/(298) = -2.5656 kJ/mol = 2565.6 J/molK
Suniverse = -193.96 + 2565.6 = 2371.6 J/molK
d)
dG = dH - TdS
dG = -764.55 - 298*-193.96/1000 = -706.75 kJ/mol
e) Find K
dG = -RT*lnK
-706.75 = -8.314*298*lnK
706.75/(8.314*298) = lnK
K = exp(0.2852) = 1.33
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