Thermodynamics unit test
A test on this unit alone, marked as a percentage and a letter grade — for the test your class is actually sitting, rather than for May. Answer everything, then submit once: seeing the answer to question 3 before attempting question 4 makes the final percentage meaningless.
Heat capacity and q = mcΔT
Temperature dependence of ΔG
ΔH°rxn from formation enthalpies
Coffee-cup calorimetry assumptions
State function
System vs surroundings
Calorimetry
Why entropy of the universe matters
Thermodynamic vs kinetic favourability
Predicting the sign of ΔS
Gibbs free energy
Endothermic vs exothermic
Short answer 1. Define or explain: Hess's Law
3 ptsShort answer 2. Define or explain: ΔG and the equilibrium constant
3 ptsShort answer 3. Define or explain: Heating and cooling curves
3 ptsShort answer 4. Define or explain: Enthalpy of reaction from bond energies
3 ptsFree response
10 ptsThis course has no free-response prompt tagged to this unit, so one from elsewhere in the course is used. It is still worth writing — the skill transfers.
A student measures initial-rate data at constant temperature for the decomposition 2 N₂O₅(g) → 4 NO₂(g) + O₂(g). Trial 1: [N₂O₅] = 0.010 M, rate = 4.8 × 10⁻⁶ M/s Trial 2: [N₂O₅] = 0.020 M, rate = 9.6 × 10⁻⁶ M/s The reaction has an activation energy of 103 kJ/mol.
Determine the order of the reaction with respect to N₂O₅, and write the rate law.
Calculate the rate constant k, including units.
Describe the reaction-energy diagram for this reaction, identifying what must be labeled on it.
Explain the effect of adding a catalyst on the activation energy and on the rate.