Question

16. The total entropy of a system and its surroundings always increases for a spontan process. This is a statement of A) the law of constant composition. B) the first law of thermodynamics. C) the second law of thermodynamics. D) the third law of thermodynamics. the law of conservation of matter. 17. The standard enthalpy of vaporization of chloroform is 29.2 kJ/mol at its normal point, 61.2°C. What is the standard change in entropy for the vaporization of chloroform at its normal boiling point? A) -29.2 J/(mol K) B) 0.477 J/(mol K) C) 477 J/(mol K) D) 87.3 J/(mol K) E) 0.0873 J(mol K) 18. At the normal boiling point of toluene, AH vap 33.2 kJ/mol and AS vap 86.5 J/(mol K). What is the normal boiling point of toluene? A) 384 K B) 116 K C) 865 K D) 287 K E) 373 K 19. In which reaction is AS expected to be positive? A) 12(g) 12(s) B) H20(0)-H20(s) C) CHOHg)+ X02(8) Co(g)+ 2Hh00) D) 202(8)+ 2S0(g)- 2S0s(8) E) none of these

Answer 1

16. The entropy of universe (system surroundings) is always increases for a spontaneous process. This statement is Second Law of thermodynamics. Option C is the right answer. T, 6 1.2°C= 61.2 + 2 73.15 = 334.35K 29200 Jmol37.3 J.mol1 .K -1 ASo - 334.35K Option D is the right answer 18. vap 33200 J.mol 86.5 J.K-mo Option A is the right answer. 384 K .mol-1

We know that the entropy of the system is the measure of disorderness. Entropy is higher for the gases than liquids. The order of entropy is 19, Gases>Liquids> Solids In this reaction, a gaseous molecule converted to a solid molecule. So entropy is higher for the reactants than the products. Hence the change in entropy is negative (B) H2O (1)H20 (s) In this reaction, a liquid molecule converted to a solid molecule. So entropy is higher for the reactants than the products. Hence the change irn entropy is negative (C) СНОН (g) + 32 02 (g) > CO, (g) + 2 H2O (1) CO2 (g) 2 H2O (I) In this reaction, a total of 2.5 gaseous molecules converted to a total of 1 gaseous molecules and 2 liquid molecules. So entropy is higher for the reactantsthan the products. Hence the change in entropy is negative (D) 2 02 (g) +2 SO (g) > 2 SO3 (g) In this reaction, a total of 4 gaseous molecules converted to a total of 2 gaseous molecules. So entropy is higher for the reactants than the products. Hence the change in entropy is negative None of these have the positive entropy change Option E is the right answer.