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18 Dec 2019

For each of the following scenarios, use a calculation to predict whether or not it will occur spontaneously. (For some cases you may need to use data from Appendix A in your textbook.)

a) 5.0 L of an ideal gas (Cv,m = 5/2 R) in a balloon at 1.5 atm, 298 K undergoes isothermal expansion against 1.0 atm until the final pressure of the gas equals the external pressure.

b) The combustion reaction for glucose at 298 K carried out in a bomb calorimeter.

c) Sublimation of 0.50 mol of dry ice at 277 K (Tsub = 277 K, ÎHo sub = 25 kJ/mol) that is left out in a room held at 298 K.

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Q1. Which of the following processes are spontaneous and which are non spontaneous.
a) The combustion of natural gas
b) Extraction of Aluminum metal from its ore
c) A ball rolling down a hill
d) A bike going up a hill

Q2. Predict the entropy change (positive or negative) for the following processes/reactions
a) a lake freezing
b) weeding a garden
c) N2(g) + 2 H2(g) ? N2H4 (g)
d) Mg(s) + 2H2O(l) ? Mg(OH)2 (s) + H2(g)

Q3. The element Cesium (Cs) freezes at 28.4 C and its molar enthalpy of fusion ΔH_fusion = 2.09 kJ/mol.
a) When molten Cs solidifies to Cs (s) at its normal melting point, is the entropy change ΔS positive or negative?
b) Calculate the entropy change S when 15.0 g of Cs(l) solidifies at 28.4 C.

Q4. Using the values for standard molar entropies ΔS_f° from the appendix in your textbook, calculate ΔS° for the following reactions.
a) Be(OH)₂ (s) ? BeO (s) + H2O (g)
b) Mg(OH)2 (s) + 2 HCl (g) ? MgCl2 (s) + 2H2O (l)
c) 2CH4(g) ? C2H6 (g) + H2(g)

Q5. Using the data in the appendix of your textbook, calculate the Gibbs free energy change ΔG° for the following reactions. In each case, indicate whether the reaction is spontaneous or not
a) H2 (g) + Cl2(g) ? 2HCl (g)
b) 2 POCl3 (g) ? 2 PCl3 (g) + O2 (g)

Q6. Consider the reaction 2 NO2 (g)---N2O4 (g)
a) Using the data in the appendix in your text, calculate the standard Gibbs free energy change (ΔG°) for the reaction at 298K.
b) For the above reaction, calculate the value of Keq at 298K
c) For the same reaction, calculate G at 298 K when the partial pressures for NO₂ and N2O4 are 0.40 atm and 0.36 atm, respectively.

Q7. Consider the reaction I2 (g) + Cl2 (g)----2 ICl (g) Kp = 81.9 at 298 K
a) Calculate the standard free energy change (ΔG°)
b) What will be the Free energy change when the above reaction is at equilibrium
c) Calculate G for the reaction at 298 K when PICl = 2.55 atm, PI2=0.325 atm and PCl2 = 0.221 atm

Q8. Consider the decomposition of Lead carbonate PbCO3 (s) ? PbO(s) + CO2 (g)
a) Calculate the Gibbs free energy change (ΔG°) for the reaction at298 K.
b) Calculate G for the reaction at 400 K.
c) Write down the equilibrium expression and calculate the value of Keq at 298 K
d) Calculate the partial pressure of CO2 at 298 K. (Hint: Look at the equilibrium expression and the value of Keq at 298 K)

Q9. For the reaction: 2Al(s) + 3/2 O2(g) ? Al2O3(s), ΔH^o_rxn = -1617 kJ/mol and ΔH^o_rxn = -1577 kJ/mol. Use this data to calculate ΔS^o_rxn reaction at 298 K.

Q10. Calculate the ΔG^o for the following reaction using the data from your text:
2SO2(g) + O2(g) ? 2SO3(g)

Q11. Using the thermodynamic data available from the Appendix(?Goâs), calculate ΔG^o rxn and calculate the equilibrium constant(K) for the reaction at 25 oC:
CaCO3(s) ? CaO(s) + CO2(g)

Q12. What is the minimum temperature required for the spontaneous conversion of CCl4(l) to CCl4(g) when ΔH°(vap) is 57.3 kJ/mol andΔS°(vap) is 164 J/(mol K)? reaction: CCl4(l) ? CCl4(g)

Q13. Given the following
Fe2O3(s) + 3CO(g) . ? 2Fe(s) + 3CO2(g) ΔG° = 29.4 kJ
3Fe2O3(s) + CO(g) . ? 2Fe3O4(s) + CO2(g) ΔG° = 61.6 kJ
Calculate ΔG° for Fe(s) + Fe2O3(s) + CO2(g) ? Fe3O4(s) +CO(g)

Q14. Calculate ΔG° rxn for 2CO(g) + O2(g) ? 2CO2(g) and then calculate ΔG for the reaction at 298K; if the pressure of CO =20. atm,P O2 = 10. atm and P CO2= 0.50 atm. Will increasing the pressure of the reactants make the reaction more or less spontaneous? Explain using your calculations and Le Chatelierâs principle.

Q15. Write the reaction for photosynthesis (production ofC6H12O6(s) and oxygen from carbon dioxide and water as a gas).Calculate ?H, ? S, and ?G for the reaction at standard state. Is the reaction spontaneous?

blackferret405

Question 2 Energy Calculations

a) Calculate the heat energy (q) when 12.0 g of water is heated from 20oC to 100oC. The

specific heat for water is given in your textbook.

b) Is the process of heating water exothermic or endothermic? Explain your answer.

Question 3 Energy Calculations

You dissolve 0.1 mol of ammonium nitrate in 100 mL of H2O. The temperature of the solution

changes from 22oC to 15oC. The specific heat capacity for water is 4.184 J/g.K. Show all

calculations on a separate sheet of paper!

a) Is this reaction endothermic or exothermic?

b) Calculate the heat, q, released or absorbed in the dissolution reaction.

c) Calculate the enthalpy change, ?Hrxn (kJ/mol), for dissolving 1 mol of ammonium nitrate.

Question 4. A gas expands from 264 mL to 971 mL at constant temperature. Calculate

the amount of work done in Joules by the gas when it expands against a constant pressure of 955

torr.

Question 5 Energy Calculations

a) The nutritional calorie (Calorie) is equivalent to 1 kcal. One pound (1.0 lb) of body fat is

equivalent to 4.1 x 103 kcal. Express this quantity in joules and kilojoules. Use

scientific notation for your answer!

b) If an athlete expends 1850 kJ/h (kilojoules per hour), how long does he have to exercise

to work off 1.0 lb of body fat?

c) The average amount of calories burned during running is 125 kcal/mile. How many

miles does this athlete have to run to burn off 1.0 lb of body fat?

Question 6

Calculate ?Ho for the following reactions at 298 K. Give the balanced thermochemical

equations and show the correct physical state in each equation. Calculate the enthalpy change

for each reaction. You will find thermochemical data in the back of your textbook in Appendix 3

(p. A-8 to A-12)

a) The formation of 1 mol of HCl (gas) from its elements

b) The formation of 1 mol of sodium chloride from its elements

c) The combustion of 1 mol glucose to water and carbon dioxide

d) HCl(g) + NH3(g) ? NH4Cl(g)

Question 7

Calculate heat of formation of SO2 under nonstandard state conditions, given the following

equations

SO2(g) +

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