Thermal Energy and Enthalpy Quiz

Which of the following best defines thermal energy?

• The energy released in chemical reactions

• The total quantity of potential and kinetic energy in a substance

• The energy required to break chemical bonds

• The amount of energy needed to raise the temperature of 1g of a substance by 1°C

In a closed system, what can be exchanged with the surroundings?

• Mass only

• Energy only

• Both mass and energy

• Neither mass nor energy

What is the enthalpy change (ΔH) for an exothermic reaction?

• ΔH > 0

• ΔH < 0

• ΔH = 0

• ΔH fluctuates

Which of the following is NOT a standard condition for enthalpy calculations?

• Pressure of 1 atm

• Temperature of 273 K

• All substances in their standard state

• Concentration of 1M for solutions

If the instantaneous rate of consumption of NH3 in a reaction is 1.8 x 10^-2 M/s, what is the corresponding rate of O2 consumption in the reaction 4NH3 + 5O2 → 4NO + 6H2O?

• A) 2.25 x 10^-2 M/s

• B) 1.44 x 10^-2 M/s

• C) 4.50 x 10^-2 M/s

• D) 9.00 x 10^-2 M/s

In the reaction 4HBr + O2 → 2Br2 + 2H2O, how does the rate of HBr decomposition compare to the rate of Br2 formation?

• A) Half

• B) Twice

• C) Equal

• D) Four times

What assumptions are made in coffee-cup calorimetry?

• A) Heat loss to surroundings is significant.

• B) The specific heat of solutions is the same as water.

• C) The density of solutions differs from water.

• D) The calorimeter is an open system.

A sample of water (45.0g) is heated from 15.0°C to 35.0°C. What is the amount of heat absorbed? (specific heat c = 4.184 J/g°C)

Which of the following correctly describes the reaction 2SO2(g) + O2(g) → 2SO3(g) with ΔH° = -198.2 kJ?

• The reaction is endothermic.

• Heat is absorbed from the surroundings.

• The reaction releases 198.2 kJ of energy per mole.

• Heat is released to the surroundings.

Which statement best describes heat (q)?

• Heat is a form of potential energy stored in chemical bonds.

• Heat is the total energy of a system, including both kinetic and potential energy.

• Heat is the transfer of thermal energy from a warmer object to a cooler one.

• Heat is the specific heat capacity of a substance multiplied by its mass.