336 STEP 5. Build Your Test-Taking Confidence
(c) Calculate the value of the rate constant. Include the units on the rate constant.
(d) Assuming the reaction is exothermic, draw and label the potential energy-level diagram for the
reaction.
Question 3.
Thermodynamic values related to the above reaction are given in the table below.
SUBSTANCE ΔHf°(kJ/mol) S°(J/mol K)
CO 2 (g) –393.5 213.7
HCN(g) 135 201.7
H 2 O(g) –241.83 188.72
H 2 O(1) –285.84 69.94
O 2 (g) 0 205.0
N 2 (g) 0 191.5
(a) Calculate the enthalpy change for this reaction.
(b) Calculate the entropy change for this reaction.
(c) Calculate the standard free energy for this reaction at 25°C.
(d) Calculate the standard free energy change, at 25°C, if liquid water formed instead of water vapor.
STOP
45422 HCN g()+→ + +O g 2222 () CO g() H O g() N g()