What is the sign of Delta H (system) and Delta S (system) if a chemical reaction

Question

What is the sign of Delta H (system) and Delta S (system) if a chemical reaction is spontaneous at all temperatures under standard conditions? a. Delta H (system) is negative, and Delta S (system) is positive. b. Delta H (system) is negative, and Delta S (system) is negative. c. Delta H (system) is positive, and Delta S (system) is positive. d. Delta H (system) is positive, and Delta S (system) is negative. e. none of these For which of the following reactions will the entropy of the system decrease? a. 2 NH_3(g) rightarrow N_2(g) + 3 H_2(g) b. 2 C(s) + O_2(g) rightarrow 2 CO(g) c. CaCO_3(s) rightarrow CaO(s) + CO_2(g) d. 2 NO_2(g) rightarrow N_2O_4(g) e. NaOH(s) rightarrow Na^+(aq) + OH^-(aq) All of the following relationships are true EXCEPT a. Delta G degree_sys = Delta H degree_sys - T Delta S degree_sys. b. Delta G degree_sys = -RT ln(K). c. Delta S degree_ = Delta S degree_sys + Delta S degree_sun. d. Delta H = Delta H degree_sys + RT ln(K). e. Delta G degree_sys = -T Delta S degree_univ.

Explanation / Answer

44) we know sponteneous means delta G < 0

the reaction is sponteneous at all temperatures hence we know delta G = delta H - T*deltaS < 0 at all T.

This is possible only when delta H <0 and delta S > 0

Hence answer : a

45) Entropy decreases if the number of moles of products formed are less than number of moles of reactants reacted. This is occuring only in reaction d

Answer : d

46) Only correct statement is c

Answer : c

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