Chapter 17 ThermoDynamics

Which of the following processes generally results in an increase in entropy (ΔS > 0)?

• Freezing of water at 0^oC

• Condensation of steam at 100^oC

• Melting of ice at 0^oC

• Formation of solid salt from dissolved ions in water

For an exothermic reaction, which of the following is true?

• ΔH > 0

• ΔH < 0

• ΔH = 0

• ΔH can be either positive or negative depending on the conditions

Which of these changes is typically associated with a positive enthalpy change (ΔH > 0)?

• Combustion of methane

• Dissolving of ammonium nitrate in water

• Formation of liquid water from steam

• Freezing of water

Which of the following conditions always leads to a spontaneous reaction (ΔG < 0)?

• ΔH < 0 and ΔS < 0 at all temperatures

• ΔH < 0 and ΔS > 0 at all temperatures

• ΔH > 0 and ΔS > 0 at low temperatures

• ΔH > 0 and ΔS < 0 at all temperatures

In an endothermic reaction where ΔS < 0, which of the following is true regarding Gibbs free energy (ΔG)?

• ΔG will be positive at all temperatures.

• ΔG will be negative at high temperatures.

• ΔG will be positive at low temperatures and negative at high temperatures.

• ΔG will be zero.

For a chemical process to be endothermic and spontaneous, which of the following must be true?

• ΔS must be positive and ΔG must be positive.

• ΔS must be positive and ΔH must be positive.

• ΔS must be negative and ΔH must be negative.

• ΔG must be negative and ΔH must be negative.