Chemistry · Unit 6 · Paper 3

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.

Paper 1 Paper 2 Paper 3

Each paper is built from this unit’s 18 terms and is the same for everyone, so a teacher can assign “Unit 6, Paper 3” and every student sits the identical test. Multiple choice is marked objectively; the written sections you mark yourself against the model answer and rubric.

Suggested time 37 min 34 points0/17 attempted

Standard enthalpy of formation

Endothermic vs exothermic

System vs surroundings

Temperature dependence of ΔG

ΔH°rxn from formation enthalpies

Calorimetry

Hess's Law

Why entropy of the universe matters

State function

Enthalpy of reaction from bond energies

Coffee-cup calorimetry assumptions

Gibbs free energy

Short answer 1. Define or explain: Predicting the sign of ΔS

3 pts

Short answer 2. Define or explain: Entropy

3 pts

Short answer 3. Define or explain: Thermodynamic vs kinetic favourability

3 pts

Short answer 4. Define or explain: Heat capacity and q = mcΔT

3 pts

Free response

10 pts

This 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.