Chapter 5 Multiple Choice Questions

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. Which one of the following definitions best describes the concept of work?

the flow of energy from one object or substance to another due to a difference in temperature correct incorrect

the flow of energy from one body to another through uniform molecular motion correct incorrect

the force associated with molecular motion correct incorrect

the random motion of molecules in a gas at low pressure correct incorrect

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. An isolated system is best described by which one of the following statements?

Neither matter nor heat can pass into or out of the system correct incorrect

The system has a boundary which allows heat to be transferred but does not allow material to pass into or out of the system correct incorrect

The system has a diathermic boundary correct incorrect

A system which has reached thermal equilibrium with its surroundings correct incorrect

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. Which one of the following statements describes a path function?

A property of a system that depends only on the current state of the system, not on the path the system took to reach that state correct incorrect

A property of a system that depends on the path taken between the initial and final states correct incorrect

The sum of kinetic and potential energy contained in a substance correct incorrect

The heat energy absorbed by a system at constant pressure correct incorrect

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. Consider the following thermodynamic properties.
i) work done on a system
ii) heat absorbed
iii) entropy
iv) enthalpy
Which of these properties are state functions?

i) and ii) only correct incorrect

i) and iii) only correct incorrect

i) only correct incorrect

iii) and iv) only correct incorrect

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. Which of the following statements best describes the Second Law of Thermodynamics?

The internal energy of the universe is constant. correct incorrect

Energy can be neither created nor destroyed. correct incorrect

When an isolated system undergoes a spontaneous change, the entropy of the system will increase. correct incorrect

At absolute zero, the entropy of a perfect crystal is considered to be zero. correct incorrect

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. A drug used to treat hypertension undergoes a decomposition reaction to give an insoluble product. Calculate the temperature at which this reaction becomes spontaneous if the enthalpy of the reaction at 298 K is 51 kJ mol^-1 and the entropy of the reaction at this temperature is 118.74 J K^-1 mol^-1.

430 K correct incorrect

2 300 K correct incorrect

0.5 K correct incorrect

430^oC correct incorrect

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. Which one of the following equations defines the enthalpy of reaction, ΔH, for a reaction occurring at constant pressure that does expansion work? All terms have their usual meanings.

ΔH = ΔU correct incorrect

ΔH = ΔU + pΔV correct incorrect

ΔH = ΔG - TΔS correct incorrect

ΔH = q + w correct incorrect

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. The combustion of methanol is described by the following equation:
CH₃OH + O₂ → CO₂ + 2H₂O
Use Hess's Law to calculate the enthalpy of combustion (ΔH_C) of methanol given the following standard enthalpies of formation (ΔH_f^θ ).
ΔH_f^θ methanol = - 238.0 kJ mol^-1
ΔH_f^θ H₂O = - 285.5 kJ mol^-1
ΔH_f^θ CO₂ = - 393.51 kJ mol^-1
ΔH_f^θ O₂ = 0 kJ mol^-1

-1203.2 kJ mol^-1 correct incorrect

-441.35 kJ mol^-1 correct incorrect

727.2 kJ mol^-1 correct incorrect

-727.2 kJ mol^-1 correct incorrect

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. Which of the following statements will always apply when a reversible chemical reaction has attained equilibrium?

All reactants will convert to products correct incorrect

The reaction proceeds alternately in the forward and reverse directions correct incorrect

The Gibbs free energy of the system reaches a minimum correct incorrect

The forward reaction will dominate over the reverse reaction correct incorrect

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. Which one of the following is an expression of the van't Hoff equation?

ln K = - ΔH^θ / RT + ΔS^θ /R correct incorrect

ΔH(T₂) = ΔH(T₁) + ΔC_p(T₂ - T₁) correct incorrect

ΔG^θ = ΔH^θ - TΔS^θ correct incorrect

ΔU = q + w correct incorrect