Thermodynamics Worksheet

1. Predict the sign of entropy change in the following processes

a) The process of carbonating water to make a soda drink

b) Condensation of water

c) Precipitation of Calcium Carbonate

d) Spray Painting

2. In the following equation indicate if ΔS is positive or negative.

a) HCl(g) → HCl(aq)

b) 2Na(s) + 2H2O (l) → 2NaOH(aq) + H2(g)

c) 2 H2(g) + O2(g) → 2 H2O(g)

3. Order the following in order of increasing S°, assuming the same temperature

a) Ethane (C2H6), Butane (C4H10), Propane (C3H8)

b) ClO4- (aq), ClO3- (aq) ClO2- (aq)

c) Heptane (C7H16), Benzene (C6H6), Cycloheptane (C7H14)

d) PF2Cl3 (g) , PF3 (g) , PF5 (g)

4. Define what it means for a reaction to be entropy driven.

5.Consider the combustion of acetlynegas:C2H2(g) + O2(g) →CO2(g) + H2O(g)(unbalanced)

a)Predict the signs ofΔH, and ΔS

b)Calculate ΔG°for the combustion of one mole of acetyleneby two different methods.

6.(from Brady,Russell and Holum)Considering thefactthat the formation of a bond between two atoms is exothermic and is accompanied byan entropy decrease,explain why all chemicalcompounds decompose into individual atoms if heated to a high enough temperature.

7.(from Brady,Russell and Holum)Gasohol is a mixture of gasoline and ethanol (C2H5OH).Calculate the maximumwork that could be obtained at 25 °C and 1 atm byburning 1 mol ofliquid ethanol. You will need to write and balance thechemical equation. Remember thatwhen a hydrocarbon burns, it reacts with oxygen to produce carbon dioxide and gaseouswater.

8. Use values given in appendix II to calculate the theoretical boiling point of methanol (CH3OH).

9. The boiling point of acetone (CH3)2CO is 56.2 °C. Given that the reaction (CH3)2CO(l) → (CH3)2CO(g) has a ΔH° = 31.9 kJ/mol, calculate the ΔS° for this reaction.

10. For the reaction I2(s) 2I(g) ΔH° =+213.6 kJ and ΔS° = +245.2J/K.

  1. Calculate ΔG° for this reaction. Is the reaction spontaneous at this temperature?
  2. Calculate ΔG at 250OC. Is the reaction spontaneous at this temperature?
  3. At what Celsius temperature will this reaction be spontaneous?
  4. Calculate the thermodynamic equilibrium for this reaction at 25OC. Will this be Kp or Kc?
  5. If this reaction occurred in a closed container at 25OC until it reached equilibrium, what would the equilibrium pressure of the I(g) be?

11.For the reaction given below, calculateΔG° usingtheΔG°fvalues given in AppendixIV. Without calculating K, determine whether this reaction will proceed to theright or to the left if the partial pressures are NO = 0.50atm, Cl2= 0.75 atm and NOCl = 0.65 atm.

2NO(g) + Cl2(g)  2NOCl(g)

12. For the reaction Ni2+(aq) + 6NH3(aq) ⇄ Ni(NH3)62+(aq), Kc = 5.6 x 108 at 25OC.

  1. What does the magnitude of the Kc tell you about the value of ΔG°

b.Calculate ΔG°.

c.Is this reaction spontaneous in the forward or reverse direction?

d.Calculate ΔGwhen [Ni(NH3)62+] = 0.020 M, [Ni2+] = 0.0020 M, and [NH3] = 0.0010 M. In which direction will the reaction proceed to achieve equilibrium?

13. Calculate the maximumamount of work that could be obtained under standard conditionsfrom the combustion of 5.00 g of sucrose (C12H22O11).

14.Calculate the ΔGat 95 °C for the reaction given below when the partial pressure ofeach gasis 0.120 atm. 2 NO(g) + Cl2(g)→2 NOCl(g)