8. Thermochemistry

Thermochemical Equations

Multiple Choice
Mothballs are composed primarily of the hydrocarbon naphthalene (C10H8). When 0.820 g of naphthalene burns in a bomb calorimeter, the temperature rises from 25.10 °C to 31.56 °C. If the heat capacity of the calorimeter is 5.11 kJ/°C, what is the change in internal energy (ΔErxn) for the combustion of naphthalene?
Multiple Choice
Using the given reactions, what is the enthalpy change (ΔH°) for the reaction: 2 CO(g) + 2 H2(g) → CO2(g) + H2O(g)?
Multiple Choice
Nitromethane (CH₃NO₂), sometimes used as a fuel for drag racing, burns according to the following reaction:

4 CH₃NO₂ (l) + 7 O₂ (g) → 4 CO₂ (g) + 6 H₂O (g) + 4 NO₂ (g) ∆Hº = – 2441.6 kJ

How much heat is released by burning 125.0 g of nitromethane (MW:61.044 g/mol)?
Multiple Choice
Consider the following reaction:
2 C₆H₆ (l) + 15 O₂ (g) → 12 CO₂ (g) + 6 H₂O (g) ∆Hº = – 6278 kJ
What volume of benzene (C₆H₆, d = 0.880 g/mL, molar mass = 78.11 g/mol) is necessary to evolve 5.19 x 10⁹ kJ of heat?
Multiple Choice
The creation of liquid methanol is accomplished by the hydrogenation of carbon monoxide:
CO (g) + 2 H₂ (g) → CH₃OH (l) ∆Hº = – 128.1 kJ
How much heat (in kJ) is released when 125.0 g CO reacts with 2.32 x 10² g H₂?
Multiple Choice
Consider two identical iron nails: One nail is heated to 95℃, the other is cooled to 15℃. The two nails are placed in a coffee cup calorimeter and the system is allowed to come to thermal equilibrium. What is the final temperature of the two nails?
Open Question
Which answer best describes the transfer of heat that occurs when 1.50 mol of H₂ reacts?