Calculate rxnH° and rxnS° for the reaction N2(g) + O2(g) 2 NO(g) from the follow
ID: 999672 • Letter: C
Question
Calculate rxnH° and rxnS° for the reaction N2(g) + O2(g) 2 NO(g) from the following values of KP:
T/K: 1900 2000 2100 2200 2300 2400 2500 2600
KP/10-4: 2.31 4.08 6.86 11.0 16.9 25.1 36.0 50.3
a) The temperature of car exhaust has been measured to be 500°C. What is the value of KP at this temperature?
b) The Southern California Air Quality District is considering requiring car manufacturers to have engines run at lower temperatures to reduce the amount of NO formed. If they require car exhaust not exceed 400°C, how much difference will this make in the amount of NO in the exhaust?
c) At what temperature does the value of rxnG change sign?
Explanation / Answer
a) Using the arrhenius equation
ln(k2/k1) = Ea/R * (1/T1 - 1/T2)
ln(4.08/2.31) = Ea/8.314 * (1/1900 - 1/2000)
Ea = 179765J
To calculate Kp at 500C = 500 + 273 = 773
ln(k2/k1) = 179765/8.314 * (1/773 - 1/1900)
ln(k2/k1) = 16.5915
k1 = 1.3397 * 10^(-11)
c) The value of Delta H and Delta S are not given to calculate the change sign temperature
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