Enthalpy, entropy and gibbs free energy!

Which of the following situations demonstrates high entropy?

• water freezing

• water vaporizing

• steam condensing to water

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

Entropy always increases when

• enthalpy decreases.
• temperature decreases.
• temperature increases.
• volume increases.

Which reaction has the greatest increase in entropy of the system?

A. HCl (g) + NH₃ (g) → NH₄Cl (s)

B. (NH₄)₂Cr₂O₇ (s) → Cr₂O₃ (s) + N₂ (g) + 4H₂O (g)

C. CaCO₃ (s) → CaO (s) + CO₂ (g)

D. I₂ (g) → I₂ (s)

• A

• B

• C

• D

• A

• B

• C

• D

ΔH value in an endothermic reaction is a positive number.

• True
• False