Unit 6: Thermodynamics
Chemistry · Unit 6 · Paper 2

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 1Paper 2Paper 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 2” 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 31 min 28 points0/17 attempted
1

Coffee-cup calorimetry assumptions

2

Endothermic vs exothermic

3

Calorimetry

4

Standard enthalpy of formation

5

Temperature dependence of ΔG

6

Hess's Law

7

Heat capacity and q = mcΔT

8

State function

9

System vs surroundings

10

ΔG and the equilibrium constant

11

Why entropy of the universe matters

12

ΔH°rxn from formation enthalpies

Short answer 1. Define or explain: Thermodynamic vs kinetic favourability

3 pts

Short answer 2. Define or explain: Gibbs free energy

3 pts

Short answer 3. Define or explain: Entropy

3 pts

Short answer 4. Define or explain: Enthalpy of reaction from bond energies

3 pts

Free response

4 pts

A student performs an experiment to determine the specific heat capacity of a metal. The student places a cube of the metal in boiling water so its temperature will be 100.0°C, then places the metal cube into a calorimeter that contains water and records the highest temperature of the water. Mass of metal cube 98.1 g Mass of water 52.0 g Initial temperature of metal cube 100.0°C Initial temperature of water 25.0°C Highest temperature of water ? The thermometer is graduated in whole degrees between the labeled marks at 30 and 40. At the highest temperature the liquid column stands halfway between the 38 and 39 marks. A particle-level representation of water molecules in the calorimeter before and after the metal cube was added is provided. In the "Before" diagram each of the three water molecules carries an arrow whose length represents its speed; in the "After" diagram the three molecules are drawn with no arrows. In a second experiment, 2940 J of thermal energy is transferred from 98.1 g of aluminum, which has a specific heat capacity of 0.897 J/(g·°C).

(a) What should the student report as the highest temperature of the water?

(b) The released exam asks the student to draw an arrow for each molecule in the "After" diagram to indicate how the speed of each molecule changes after the metal cube is added. Describe the arrows you would draw compared with those in the "Before" diagram, and explain why.

(c) Assuming the metal transfers 2940 J of thermal energy to the water, calculate the specific heat of the metal in J/(g·°C).

(d) Explain how the magnitude of the temperature change of the aluminum, |ΔT_Al|, compares with the magnitude of the temperature change of the metal in the original experiment.