A. Which one of the following processes produces a decrease in the entropy of the system? A) boiling water to form steam B) dissolution of solid KCl in water C) mixing of two gases D) freezing water to form ice E) melting ice to form water

ANSWER PARTS A, B, C, & D

A. Which one of the following processes produces a decrease in the entropy of the system?

A) boiling water to form steam

B) dissolution of solid KCl in water

C) mixing of two gases

D) freezing water to form ice

E) melting ice to form water

B. ΔS is positive for the reaction __________.

A) 2H2 (g) + O2 (g) → 2H2O (g)

B) 2NO2 (g) → N2O4 (g)

C) CO2 (g) → CO2 (s)

D) BaF2 (s) → Ba2+ (aq) + 2F- (aq)

E) 2Hg (l) + O2 (g) → 2HgO (s)

C. For the reaction

C2H6 (g) → C2H4 (g) + H2 (g) ΔH° is + 137 kJ/mol and ΔS° is +120 J/K ∙ mol. This reaction is __________.

A) spontaneous at all temperatures

B) spontaneous only at high temperature

C) spontaneous only at low temperature

D) nonspontaneous at all temperatures

D. Which of these processes lead(s) to an increase in entropy? (treat all gases as ideal). Circle all that apply.

A) The pressure of 1 mole of oxygen gas is allowed to double isothermally.

B) Carbon dioxide is allowed to expand isothermally to 10 times its original volume.

C) The temperature of 1 mol of helium is increased 25 °C at constant pressure.

D) Nitrogen gas is compressed isothermally to half its original volume.

E) A glass of water loses 100 J of energy reversibly at 30 °C.