5 Steps to a 5 AP Chemistry

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()