7F CC Amnesty Day

Entropy increases from solid, liquid to gas. Why?

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

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 of the reactions below has a negative ∆S?

• CuCO₃ (s) + 2HCl (aq) → CuCl₂ (aq) + CO₂ (g) + H₂O (l)

• C (s) + O₂ (g) → CO₂ (g)

• CuO (s) + H₂SO₄ (aq) → CuSO₄ (aq) + H₂O (l)

• BaCl₂ (aq) + Na₂SO₄ (aq) → BaSO₄ (s) + 2NaCl (aq)

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.

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

• +ΔH and +ΔS

• +ΔH and -ΔS

• -ΔH and -ΔS

• -ΔH and +ΔS

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