AP Thermodynamics and Thermochemistry 2

Question 1

Calculate ΔH°rxn for the combustion of methane: CH₄(g) + 2O₂(g) → CO₂(g) + 2H₂O(l). Given ΔH°f values: CH₄(g) = −74.8 kJ/mol, CO₂(g) = −393.5 kJ/mol, H₂O(l) = −285.8 kJ/mol.

Accepted Answer

−890.3 kJ/mol

Answer

−504.0 kJ/mol

Answer

+890.3 kJ/mol

Answer

−815.5 kJ/mol

Question 2

For the reaction: N₂(g) + 3H₂(g) → 2NH₃(g). ΔH° = −92 kJ and ΔS° = −198 J/K. At what temperature does this reaction change from spontaneous to non-spontaneous?

Accepted Answer

464 K

Answer

232 K

Answer

198 K

Answer

925 K

Question 3

A bomb calorimeter experiment burns 1.00 g of glucose (C₆H₁₂O₆, MM = 180.2 g/mol) and releases 15.57 kJ of heat, raising the temperature by 1.40°C. What is the heat capacity of the calorimeter?

Accepted Answer

11.1 kJ/°C

Answer

15.57 kJ/°C

Answer

7.79 kJ/°C

Answer

21.8 kJ/°C

Question 4

Calculate ΔS° for the reaction: 2H₂(g) + O₂(g) → 2H₂O(l). S° values: H₂(g) = 130.7 J/mol·K, O₂(g) = 205.1 J/mol·K, H₂O(l) = 70.0 J/mol·K.

Accepted Answer

−326.5 J/K

Answer

+326.5 J/K

Answer

−257.5 J/K

Answer

+257.5 J/K

Question 5

For a reaction at 298 K with ΔG° = −25.0 kJ/mol, what is the equilibrium constant K?

Accepted Answer

K ≈ 2.48 × 10⁴

Answer

K ≈ 5.47 × 10⁻³

Answer

K ≈ 1.00

Answer

K ≈ 1.61 × 10²

Question 6

The specific heat capacity of iron is 0.449 J/(g·°C). How much heat is required to raise the temperature of a 250. g iron bar from 20.0°C to 150.°C?

Accepted Answer

14,600 J

Answer

7,300 J

Answer

29,200 J

Answer

3,650 J

Calculate ΔH°rxn for the combustion of methane: CH₄(g) + 2O₂(g) → CO₂(g) + 2H₂O(l).Given ΔH°f values: CH₄(g) = −74.8 kJ/mol, CO₂(g) = −393.5 kJ/mol, H₂O(l) = −285.8 kJ/mol.

Calculate ΔH°rxn for the combustion of methane: CH₄(g) + 2O₂(g) → CO₂(g) + 2H₂O(l).
Given ΔH°f values: CH₄(g) = −74.8 kJ/mol, CO₂(g) = −393.5 kJ/mol, H₂O(l) = −285.8 kJ/mol.