Exam 5: Thermochemistry

A student used a bomb calorimeter to determine the heat of combustion of an unknown compound. If the student ignored the heat capacity of the bomb calorimeter, the heat capacity of the unknown compound would be ________ the accepted value.

A system initially has an internal energy U of 504 J. It undergoes a process during which it releases 111 J of heat energy to the surroundings, and does work of 222 J. What is the final energy of the system, in J?

The bond enthalpy of the Br-Cl bond is equal to ΔH°_rxn for the following reaction. BrCl(g) → Br(g) + Cl(g) Using the following data, what is the bond enthalpy of the Br-Cl bond?

A system that does no work but which transfers heat to the surroundings has

Styrene, C₈H₈, is one of the substances used in the production of synthetic rubber. When styrene burns in oxygen to form carbon dioxide and liquid water under standard-state conditions at 25°C, 42.15 kJ are released per gram of styrene. Find the standard enthalpy of formation of styrene at 25°C. ΔH°_f(CO₂(g)) = -393.5 kJ/mol, ΔH°_f(H₂O(l)) = -285.8 kJ/mol

An important step in the synthesis of nitric acid is the conversion of ammonia to nitric oxide according to the following balanced chemical equation. What is ΔH°_rxn for this reaction? 4NH₃(g) + 5O₂(g) → 4NO(g) + 6H₂O(g)

The specific heat (capacity) is

A Snickers® candy bar contains 280 Calories, of which the fat content accounts for 120 Calories. What is the energy of the fat content, in kJ? (1 cal = 4.184 J)

A system absorbs 21.6 kJ of heat while performing 6.9 kJ of work on the surroundings. If the initial internal energy, U, is 61.2 kJ, what is the final value of U?

The sign of q when heat is absorbed by the system is ________.

An exothermic reaction causes the surroundings to

Suppose a sample of gas undergoes the following change of state. Which statement(s) is/are true concerning this change of state?

The heat of solution of ammonium chloride is 15.2 kJ/mol. If a 6.134-g sample of NH₄Cl is added to 65.0 mL of water in a calorimeter at 24.5°C, what is the final temperature of the solution? The specific heat of water is 4.18 J/g·°C and the heat capacity of the calorimeter is 365 J/°C.

Ethylene glycol, used as a coolant in automotive engines, has a specific heat capacity of 2.42 J/g°C. Calculate q when 3.65 kg of ethylene glycol is cooled from 132°C to 85°C.

What is the standard enthalpy change for the decomposition of one mole of SO₃? 2SO₂ + O₂→ 2SO₃ ΔH°_rxn = -198 kJ/mol

A system that does no work but which receives heat from the surroundings has

How much heat is required to raise the temperature of 12.0 g of water from 15.4°C to 93.0°C? The specific heat of water is 4.184 J/g·°C.

In an endothermic process, heat is absorbed by the system.

The work done on the surroundings by the expansion of a gas is w = -PΔV.

Which type of system may transfer energy, but not mass, to the surroundings?