State Functions: Thermodynamics

Indicate which one of the following reactions results in a negative ΔSsys. a. H2O(g) D H2O(s) b. CaCO3(s) D CaO(s) + CO2(g) c. CuSO4(H2O)5 (s) D CuSO4(s) + 5H2O(g) d. 14O2(g) + 3NH4NO3(s) + C10H22(l) → 3N2(g) + 17H2O(g) + 10CO2(g) e. CO2(aq) D CO2(g)

H2O(g)-><- H2O(s)

1. Which of the following is in the correct order of standard state entropy? I. Liquid water < gaseous water II. Liquid water < solid water III. NH3 < H2

I only

Which of the following will have the greatest standard molar entropy (S°)? a. NH3(g) b. H2O(l) c. He(g) d. CaCO3(s) e. C(s, graphite)

NH3(g)

Indicate which of the following has the lowest standard molar entropy (S°) a. CH4(g) b. Na(s) c. CH3CH2OH() d. He(g) e. H2O(s)

Na(s)

Are either of the above reactions endergonic? If so, which one(s) and why?

The reaction with glutamate and NH3 in #2. The change in ∆G (free energy) is positive, meaning free energy is absorbed, making this reaction endergonic

Given the following information: 2NO(g) + O2(g) ---> 2NO2(g) ΔH = -116 kJ 2N2(g) + 5O2(g) + 2H2O(ℓ) ---> 4HNO3(aq) ΔH = -256 kJ N2(g) + O2(g) ---> 2NO(g) ΔH = +183 kJ Calculate the enthalpy change for the reaction below: 3NO2(g) + H2O(ℓ) ---> 2HNO3(aq) + NO(g) ΔH = ???

ΔH = -137 kJ

Calculate the enthalpy for this reaction: 2C(s) + H2(g) ---> C2H2(g) ΔH° = ??? kJ Given the following thermochemical equations: C2H2(g) + 5⁄2O2(g) ---> 2CO2(g) + H2O(ℓ) ΔH° = -1299.5 kJ C(s) + O2(g) ---> CO2(g) ΔH° = -393.5 kJ H2(g) + 1⁄2O2(g) ---> H2O(ℓ) ΔH° = -285.8 kJ

+226.7 kJ

2NO2(g) equilibr.gif (63 bytes) N2O4(g

-175.83 J/K

Indicate which of the following has the highest entropy at 298 K. a. 0.5 g of HCN b. 1 mol of HCN c. 2 kg of HCN d. 2 mol of HCN e. All of the above have the same entropy at 298 K

2 kg of HCN

N2(g) + O2(g) equilibr.gif (63 bytes) 2NO(g)

24.77 J/K

Calculate the Gibbs free energy change (G) for the following chemical reaction: ATP ADP + Pi The reaction occurs at 68 °F, the change in heat (H) = 19,070 cal, and the change in entropy (S) = 90 cal/K.

68 °F = 293 K, therefore the equation is set up in the following way: G = H - TS G = 19,070 cal - (293 K) (90 cal/K) G = -7300 cal = -7.3 kcal

Calculate the Gibbs free energy change (G) for the following chemical reaction: glutamate + NH3 glutamine + H2O The reaction occurs at 68 °F, the change in heat (H) = 4103 cal, and the change in entropy (S) = 2.4 cal/K.

68 °F = 293 K, therefore the equation is set up in the following way: G = H - TS G = 4103 cal - 293 K (2.4 cal/ K) G = 3399.8 cal = 3.4 kcal

Calculate the standard-state entropy of reaction for the following reactions and explain the sign of deltaS� for each reaction. (a) Hg(l) equilibr.gif (63 bytes) Hg(g)

98.94 J/K

Indicate which one of the following reactions result in a positive ΔSsys. a. AgNO3(aq) + NaCl(aq) D AgCl(s) + NaNO3(aq) b. H2O (g) + CO2 (g) D H2CO3 (aq) c. H2(g) + I2(g) D 2 Hl(g) d. C2H2O2(g) D 2 CO(g) + H2(g) e. H2O(g) D H2O(l)

C2H2O2(g) -> <- 2CO(g) + H2(g)

state function

a property whose value does not depend on the path taken to reach that specific value. In contrast, functions that depend on the path from two values are call path functions. Both path