Laws of Thermodynamics

Entropy increases from solid, liquid to gas. Why?

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

Which represents a decrease in entropy?

• sublimation of CO₂

• boiling water

• condensation of steam on cold glass

• NaCl dissolving in water

The entropy will usually increase when

• a molecule is broken into two or more smaller molecules

• a reaction occurs that results in an increase in the number of moles of gas

• a solid changes to a liquid

• all of these

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)

Entropy is a measure of

• accuracy

• precision

• the disorder of a system

• the attraction of a nucleus for an electron

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.

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.

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.

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

• +ΔH and +ΔS

• +ΔH and -ΔS

• -ΔH and -ΔS

• -ΔH and +ΔS

Which of the following situations demonstrates high entropy?

• water freezing

• water vaporizing

• steam condensing to water