Styrene is produced by catalytic dehydrogenation of ethyl- benzene at high temperature in the presence of superheated steam. (a) Find ÄH°rxn, ÄG °rxn, and ÄS °rxn, given these data at 298 K: (b) At what temperature is the reaction spontaneous?
What are Delta G and K at 600 degrees?
I only need help with K at 600 degrees. Thank you. I thought it was 9.9 x 10^2 but it was marked wrong.•Chemistry - Dalton, Saturday, November 7, 2015 at 3:38pm
data:
Given the following data, what is the delta Hrxn, delta Grxn and delta Srxn at 298 K. Ethylbenzene, C6H5--CH2CH3 : delta Ht = -12.5 kJ/mol, delta Gt = 119.7 kJ/mol and S = 255 J/mol*K Styrene, C6H5--CH==CH2 : delta Ht = 103.8 kJ/mol, delta Gt = 202.5 kJ/mol and S = 238 J/mol*K
To find the ÄH°rxn (change in enthalpy), ÄG°rxn (change in Gibbs free energy), and ÄS°rxn (change in entropy) at 298 K, we can use the following equations:
ÄH°rxn = ΣΔH°f(products) - ΣΔH°f(reactants)
ÄG°rxn = ΣΔG°f(products) - ΣΔG°f(reactants)
ÄS°rxn = ΣS°(products) - ΣS°(reactants)
Using the given data, we have:
For ethylbenzene:
ΔH°f = -12.5 kJ/mol
ΔG°f = 119.7 kJ/mol
S° = 255 J/mol*K
For styrene:
ΔH°f = 103.8 kJ/mol
ΔG°f = 202.5 kJ/mol
S° = 238 J/mol*K
(a) To find ÄH°rxn:
ÄH°rxn = (ΔH°f(styrene) - ΔH°f(ethylbenzene))
= (103.8 kJ/mol - (-12.5 kJ/mol))
= 116.3 kJ/mol
(b) To find ÄG°rxn:
ÄG°rxn = (ΔG°f(styrene) - ΔG°f(ethylbenzene))
= (202.5 kJ/mol - 119.7 kJ/mol)
= 82.8 kJ/mol
(c) To find ÄS°rxn:
ÄS°rxn = (S°(styrene) - S°(ethylbenzene))
= (238 J/mol*K - 255 J/mol*K)
= -17 J/mol*K
Now, to find the equilibrium constant (K) at 600 degrees Celsius, we will need to convert the temperature to Kelvin.
Temperature (K) = 600 degrees Celsius + 273.15
= 873.15 K
Using the equation: ΔG°rxn = -RTln(K)
where:
ΔG°rxn = ÄH°rxn - TΔS°rxn
we can rearrange the equation to solve for K:
K = e^(-ΔG°rxn / RT)
By plugging in the values for ΔG°rxn, R (gas constant, 8.314 J/mol*K), and T (temperature in Kelvin), we can calculate K.
K = e^(-ΔG°rxn / (R * T))
= e^(-(82.8 kJ/mol) / (8.314 J/mol*K * 873.15 K))
≈ 9.21 × 10^-19613
It is important to note that the value calculated for K (9.21 × 10^-19613) is extremely small, borderline zero. It is possible that there was an error in your calculation or the values given.