thermo and nuclear review 1

What does Gibbs Free Energy tell us?

• How much energy is given off by a reaction.

• The tendency of a reaction to become "random"

• How spontaneous a reaction is.

Spontaneous reactions may be extremely slow.

• True
• False

Which of the following would most likely lead to a spontaneous reaction.

• A high negative enthalpy.

• A low negative enthalpy.

• A high positive enthalpy.

• A low positive enthalpy.

A reaction has a positive ΔH and a positive ΔS. Which of the following is true?

• It will be spontaneous at all temperatures.
• It will be nonspontaneous at all temperatures.
• It will be spontaneous at low temperatures.
• It will be spontaneous at high temperatures.

Your enthalpy is +20 and your entropy is +5. Which temperature will give a spontaneous reaction?

• 0

• 4

• 8

Your enthalpy is high and negative but your entropy is also negative. What type of temperature would you want to get a spontaneous reaction?

• low

• high

Your enthalpy is positive and your entropy is positive. What type of temperature would you want to ensure a spontaneous reaction.

• very high

• very low

Which combination of ΔH and ΔS NEVER has a spontaneous reaction?

• +ΔH and +ΔS

• +ΔH and -ΔS

• -ΔH and -ΔS

• -ΔH and +ΔS

Your enthalpy is -20 and your entropy is -8. Which temperature will give you a spontaneous reaction?

• 1

• 3

• 5

6. The formation ½ A₂ + 2 B₂ + C --> CAB₄ has an enthalpy of formation of -104 kJ and a change in entropy of -60.8 J/K at 30 °C. What is the free energy and spontaneity of the reaction?

• -85.6 kJ, spontaneous

• -18.3 kJ, not spontaneous

• +18.3 kJ, spontaneous

• +85.6 kJ, not spontaneous