Given the values of Hrxn, Srxn, and T below, determine Suniv. a. H rxn= 90 kJ ,

Question

Given the values of Hrxn, Srxn, and T below, determine Suniv.

a. Hrxn= 90 kJ , Srxn= 145 J/K , T= 303 K Express your answer using two significant figures. Predict whether or not the reaction in part A will be spontaneous.

b. Hrxn= 90 kJ , Srxn= 145 J/K , T= 750 K Express your answer using one significant figure. Predict whether or not the reaction in part B will be spontaneous.

c. Hrxn= 90 kJ , Srxn= 145 J/K , T= 303 K Express your answer using two significant figures. Predict whether or not the reaction in part C will be spontaneous.

d. Hrxn= 90 kJ , Srxn= 145 J/K , T= 391 K Express your answer using two significant figures. Predict whether or not the reaction in part D will be spontaneous.

Explanation / Answer

G = H - TS

G free energy change can be calculated by substituting enthalpies and entropies of reaction and a Kelvin temperature into the Gibbs equation. When G is positive the reaction is non spontaneous and if  G is negative the reaction is spontaneous .

Question a

G = 90 x 103 - 303 x 145 = 46.06 x 103 J

G is positive . This reaction is non-spontaneous

Question b

G = 90 x 103 - 750 x 145 = -18.75 x 103 J

G is positive . This reaction is spontaneous

Question C

G = -90 x 103 - 303 x (-145) = -46.06 x 103 J

G is positive . This reaction is spontaneous

Question D

G = -90 x 103 - 391 x 145 = -146.69 x 103 J

G is positive . This reaction is spontaneous

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