15.3

Entropy increases from solid, liquid to gas. Why?

• Molecular disorder increases
• Molecular randomness decreases
• Molecules are more energetic
• Molecules are more reactive

Which sample has the lowest entropy?

HINT - Look at the phase of each chemical....

• 1 mole of KNO₃(l)

• 1 mole of KNO₃(s)

• 1 mole of H₂O(l)

• 1 mole of H₂O(g)

What phase of matter has the most entropy?

• solid

• liquid

• gas

What information do we need to perform a calculation of Gibbs Free Energy?

• Enthalpy of the reaction.

• Entropy of the reaction.

• The temperature of the reaction in Kelvin.

• All of the above are needed.

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.

Which of the following is the most thermodynamically favorable?

• negative enthalpy and negative entropy

• negative enthalpy and positive entropy

• positive enthalpy and negative entropy

• positive enthalpy and positive entropy

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

• +ΔH and +ΔS

• +ΔH and -ΔS

• -ΔH and -ΔS

• -ΔH and +ΔS

An exothermic reaction involves

• Breaking weak bonds to form weaker bonds

• breaking weak bonds to form stronger bonds

• breaking strong bonds to form weak bonds

• breaking strong bonds to form strong bonds