CHM1 12 End-of-Chapter Problems Collection

Chapter 12 Problems

C(s, graphite) + `O_2 -> CO_2 DeltaH^0 = -393.5 kJ"/"mol`

`CO_2 -> C(s, diamond) + O_2 DeltaH^0 = + 395.41 kJ"/"mol`

5. 1.150 g of sucrose goes through combustion in a bomb calorimeter. If the temperature rose from 23.42°C to 27.64°C and the heat capacity of the calorimeter is 4.90 kJ/°C, then determine the heat of combustion of sucrose, `C_(12)H_(22)O_(11)`, in kj per mole of `C_(12)H_(22)O_(12)`.

6. Without doing a calculation, predict whether the entropy change will be positive or negative.

a)      `C_2H_6(g) + 7/2O_2(g) -> 3H_2O(g) + 2CO_2(g)`

b)      `3C_2H_2(g) -> C_6H_6(l)`

c)      `C_^H_(12)O_6(s) + 6O_2(g) -> 6CO_2(g) + 6H_2O(l)`

7. Calculate the standard-state free energy of formation for the H₂O₂(l) from H₂ and O₂, given the following values:
`DeltaG_f` (`H_2`): 0 kJ/mol
`DeltaG_f` (`O_2`): 0 kJ/mol
`DeltaG_f` (`H_2O_2(l)`): -120.4 kJ/mol

8.

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10. The change in internal energy for the combustion of 1.0 mol of octane at a pressure of 1.0 atm is 5084.3 kJ. If the change in heat energy is 5074.1 kJ, how much work is done during the combustion?

11. The propane fuel (`C_3H_8`) used in gas barbeques burns according to the following thermochemical equation: `C_3H_8(g) + 5O_2(g) -> 3CO_2 (g) + 4H_2O (g)`                   `DeltaH_(rxn)= -2217 kJ`

If a pork roast must absorb 160 kJ to fully cook, and if only 10% of the heat produced by the BBQ is actually absorbed by the roast, what mass of `CO_2` is emitted into the atmosphere during the grilling of the porkroast?

12. A 5.1g piece of gold jewelry is removed from water at 100.0°C and placed in a coffee-cup calorimeter containing 16.9 g of water at 22.5°C. The equilibrium temperature is 23.2°C. The calorimeter constant is known to be 1.54 J/°C. What is the specific heat of this piece of jewelry? The specific heat of pure gold is 0.129J/g°C. Is the jewelery pure gold?

13. Use the tabulated bond energies to estimate the enthalpy of the following reaction: `CO + H_2O -> CO_2 + H_2`

14. Given the following data calculate the heat of combustion in kJ/mol of xylose, `C_5H_(10)O_5(s)`, used in a bomb calorimetry experiment: mass of `C_5 H_(10) O_5(s) = 1.250 g`, heat capacity of calorimeter = 4.728 kJ/°C, Initial Temperature of the calorimeter = 24.37°C, Final Temperature of calorimeter = 28.29°C.

15.  In the following changes is there an increase in entropy?

a) The freezing of water

b) `l_2(s) -> l_2(g)`

c) The sublimation of dry ice, solid `CO_2`

d) `PCl_5 (g) -> PCl_3(g) + Cl_2(g)`

16. Using the standard molar entropies, calculate the value of `DeltaS` for the following reaction:

`4HCl(g) + O_2(g) -> 2Cl_2(g) + 2H_2O(g)` .

17. Consider the following reaction:
`CaCO_3 -> CaO + CO_2`
At what temperature will this reaction become spontaneous? Note: Assume `DeltaH_r^°` and `DeltaS_r^°` are temperature independent. (Hint: What variable tells us for sure whether the reaction is spontaneous or not?)
Given values:

Answers to Problems 1-9

 

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