CHEM: THERMODYNAMICS-ENTROPHY- ENTHALPY STUDY MODULE

If ∆H = 498 kJ and ∆S = 319 J/K, the spontaneity of the reaction depends on temperature. Above what temperature will the reaction be spontaneous?

1.29 × 10^3 °C

What is the change in entropy of the surroundings (∆Ssurr) for the synthesis of HF at 25°C? H2(g) + F2(g) → 2 HF(g) ∆H = −537 kJ

1.80 kJ/K

Given ∆Ssystem equals 345 J and ∆Ssurroundings equals −225 J, what is ∆Suniverse?

120. J

If ∆H = −251 kJ and ∆S = −391 J/K, the spontaneity of the reaction depends on temperature. Below what temperature in Celsius will the reaction be spontaneous?

369 °C

What is the change in Gibbs free energy, ∆G, at 500°C given ∆H = −92.22 kJ and ∆S = −198.75 J/K? N2(g) + 3 H2(g) → 2 NH3(g)

61.41 kJ

What is the change in entropy of the surroundings (∆Ssurr) for the reaction of SO2 and O2 at 25.0°C? 2 SO2(g) + O2(g) → 2 SO3(g) ∆H = −196 kJ

658 J/K

Which reaction has a decrease in entropy?

CO(g) + 3 H2(g) → CH4(g) + H2O(g)

Which reaction has an increase in entropy?

CaCO3(s) → CaO(s) + CO2(g)

Which one of the following is a spontaneous process at 25°C?

Ice melting

For a reaction, ∆H is positive and ∆S is negative. Which choice best describes when the reaction will be spontaneous?

Never

Which statement is true about the entropy for condensation?

The entropy decreases during condensation, so the change in entropy is a negative value.

Which statement is true about the entropy for vaporization?

The entropy increases during vaporization, so the change in entropy is a positive value.

Which one of the following is a nonspontaneous process?

Water decomposing to its elements at 25°C and 1 atm

What are the values of ∆H and ∆S so that Gibbs free energy, ∆G, is negative at all temperatures?

∆H < 0 and ∆S > 0

What are the values of ∆H and ∆S so that Gibbs free energy, ∆G, is positive at all temperatures?

∆H > 0 and ∆S < 0

What is the standard entropy change for the reaction? 2 NO2(g) ⇌ N2O4(g)

−176 J/K

What is the standard entropy change for the reaction? CO(g) + 3 H2(g) → CH4(g) + H2O(g)

−216 J/K

If ∆H = 348 kJ and ∆S = 164 J/K, the spontaneity of the reaction depends on temperature. Above what temperature in Celsius will the reaction be spontaneous?

1.85 × 103 °C

What is the change in entropy of the surroundings (∆Ssurr) for the synthesis of water at 25.0 °C? 2 H2(g) + O2(g) → 2 H2O(g) ∆H = −572 kJ

1.92 kJ/K

What is the standard entropy change for the reaction? 4 NH3(g) + 5 O2(g) → 4 NO(g) + 6 H2O(g)

181 J/K

What is the change in enthalpy of the reaction when the change in entropy of the surroundings (∆Ssurr) is −606 J/K at 25°C? N2(g) + O2(g) → 2 NO(g)

181 kJ

For a reaction, ∆H is negative and ∆S is positive. Which choice best describes when the reaction will be spontaneous?

At all temperatures For a spontaneous reaction, ∆G < 0. The equation that relates ∆G, ∆H, and ∆S is ∆G = ∆H − T∆S. If ∆H is negative and ∆S is positive, then ∆G will always be negative and the reaction will be spontaneous, regardless of the temperature.

For a reaction, ∆H and ∆S are both positive. Which choice best describes when the reaction will be spontaneous?

At high temperatures

For a reaction, ∆H and ∆S are both negative. Which choice best describes when the reaction will be spontaneous?

At low temperatures

If ∆Suniverse and ∆Ssystem are both positive, what do we know about the sign of ∆Ssurroundings?

∆Ssurroundings can be positive or negative, depending on the magnitude of the values or the system and surroundings.

What is the enthalpy of the reaction when the change in entropy of the surroundings (∆Ssurr) is 380. J/K at 25°C? 2 NO(g) + O2(g) → 2 NO2(g)

−113 kJ

What is the change in Gibbs free energy, ∆G, at 25°C given ∆H = −92.22 kJ and ∆S = −198.75 J/K? N2(g) + 3 H2(g) → 2 NH3(g)

−32.99 kJ

What is the enthalpy of the reaction when the change in entropy of the surroundings (∆Ssurr) is 1.32 kJ/K at 25°C? C(s, graphite) + O2(g) → CO2(g)

−393 kJ

What is the change in Gibbs free energy, ∆G, at 25°C given ∆H = −57.20 kJ and ∆S = −175.83 J/K? 2 NO2(g) → N2O4(g)

−4.80 kJ

Given ∆Ssystem equals 412 J and ∆Suniverse equals −186 J, what is ∆Ssurroundings?

−598 J