Thermodynamics Quizs

What key equations summarize internal energy and enthalpy?

• The equations involving U, ΔU, H, and ΔH provide shorthand for internal energy and enthalpy.

• The equations involving P, V, T, and S summarize thermodynamic processes.

• The equations involving F, W, Q, and m describe mechanical work and energy.

• The equations involving E, C, T, and R relate to kinetic energy and temperature.

What is the difference between open, closed, and isolated systems regarding mass and energy flow?

• Mass and energy can flow in and out of open systems, only energy can flow in and out of closed systems, and neither can flow in or out of isolated systems.

• Mass can flow in and out of open systems, while closed systems allow both mass and energy to flow, and isolated systems allow no flow at all.

• Only mass can flow in and out of open systems, while closed systems allow mass and energy to flow, and isolated systems allow energy flow only.

• Mass and energy can flow in and out of both open and closed systems, while isolated systems allow for mass flow only.

How does temperature influence Gibbs free energy?

• It has no effect on Gibbs free energy.

• Temperature affects Gibbs free energy through the TΔS term, impacting reaction spontaneity.

• Higher temperatures always increase Gibbs free energy.

• Temperature only affects enthalpy, not Gibbs free energy.

What does negative heat (---) indicate in exothermic processes?

• Negative heat indicates that heat is absorbed by the system.

• Negative heat indicates that heat is released from the system.

• Negative heat leaves the system in exothermic processes like combustion.

• Negative heat has no effect on the system.

What are some ballpark values for different energy calculations?

• Combustion reactions are 1000s of kJ negative; phase changes are tens of kJ/mole.

• Combustion reactions are 100 kJ positive; phase changes are hundreds of kJ/mole.

• Combustion reactions are 10 kJ negative; phase changes are thousands of kJ/mole.

• Combustion reactions are 500 kJ negative; phase changes are 50 kJ/mole.

What is a key takeaway for combustion reactions?

• The answer is typically a large positive number.

• The answer is typically a small negative number.

• The answer is typically a large negative number.

• The answer is typically zero.

What should you remember about formation and decomposition reactions?

• ΔH_f is per mole and must be multiplied by the number of moles for the correct energy amount.

• Formation reactions always release energy, while decomposition reactions always absorb energy.

• The total energy change is always zero for formation and decomposition reactions.

• ΔH_f is only applicable to decomposition reactions.

What is the exception for bond energy calculations?

• Bond energy calculations use product minus reactant.

• Bond energy calculations use reactant minus product.

• Bond energy calculations use average bond energies.

• Bond energy calculations do not consider ionic bonds.

How does the presence of gases affect entropy?

• Gases have a minimal impact on entropy; changes in solid quantity dominate ΔS.

• Gases have a disproportionate impact on entropy; changes in gas quantity dominate ΔS.

• Gases do not affect entropy; only liquids influence ΔS.

• Gases reduce entropy by increasing order in a system.

What does a negative ΔG_sys indicate?

• A negative ΔG_sys indicates that a reaction occurs.

• A negative ΔG_sys indicates that the reaction is at equilibrium.

• A negative ΔG_sys indicates that the reaction is non-spontaneous.

• A negative ΔG_sys indicates that the reaction requires energy input.