Study questions -chapt 181. Which of the following changes lead to a decrease in entropy?a. sugar dissolving in coffeeb. mixing of pure gasesc. the sublimation (vaporization) of dry ice (solid carbon dioxide)d. melting snowe. halving the volume of a gas2 At what temperatures will a reaction be spontaneous if A,H° = +117 kJ and A,S° =-35 J/K?3. Calculate A,G° for the following reaction at 425 °C,(8)I + (3)*H_, (3)IHgiven K= 0.018. (R=8.314 J/K-mol)%3D4. For a reaction, A,H° = -208.8 kJ and A,S° =-308.2 J/K. At what temperature will A,G° = 0.00 kJ?%3D%3D5. What is the sign of AH(system) and AS(system) if a chemical reaction is spontaneous at all temperatures under standard conditions?HV ε(system) is negative, and AS(system) is positive.HV °q(system) is negative, and AS(system) is negative.HV(system) is positive, and AS(system) is positive.HV P(system) is positive, and AS(system) is negative.e. none of these6. For which of the following reactions will the entropy of the system decrease?a. 2 NH3(g) → N2(g) + 3 H2(g)b. 2 C(s) + O2(g) → 2 CO(g)C. CACO3(s) → CaO(s) + CO2(g)d. 2 NO2(g) → N20:(g)e. NaOH(s) → Na (aq) + OH (aq)7. Which of the following linear chain alcohols is likely to have the highest standard entropy in the liquid state?a. CH;OH1. 2.Chapt 18b. CH;CH2OHс. CH-CH.CH-OНd. CH;CH2CH2CH2OHe. CH3CH2CH2CH2CH2OH8. The following processes occur spontaneously at 25 °C. Which of these processes is/are endothermic?NH,NO3 dissolving in water (which is accompanied by a cooling of the water).the expansion of a real gas into a vacuum (which is accompanied by a cooling of the1.2.gas).3. liquid water in an ice cube tray freezing into ice after being placed in a freezer.a. 1 onlyb. 2 onlyc. 3 onlyd. 1 and 2e. 1, 2, and 39. For the combustion of acetylene at 298.15 K,2 C¿H2(g) + 5 O2(g) → 4 CO2(g) + 2 H2O(g)calculate AS (universe) given AS (system) = -194.6 J/K and AH°(system) = -2511.2 kJ.10. If a chemical reaction occurs in a direction that has a positive change in entropy thena. the change in enthalpy must be negative.b. the reaction must be spontaneous.c. heat goes from the system into the surroundings.d. the reaction must be exothermic.e. the disorder of the system increases.

Entropy is the measure of randomness or disorder in a system. As entropy refers to the degree of disorderness of a system, the greater the volume of a gas, the greater its entropy. The entropy of a system is directly proportional to its volume. Hence a decrease in the volume of a gas leads to a decrease in its entropy. Ultimately, if the volume of a given mass of gas is halved, its entropy decreases according. Therefore the answer is => e. Halving the volume of a gas.