Given the values of H rxn, S rxn, and T below, determine S univ. A. H rxn= 84 kJ

Question

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

A. Hrxn= 84 kJ , Srxn= 144 J/K , T= 300 K

Express your answer using two significant figures.

Suniv =

Predict whether or not the reaction will be spontaneous.

B. Hrxn= 84 kJ , Srxn= 144 J/K , T= 751 K

Express your answer using one significant figure.

Suniv =

Predict whether or not the reaction will be spontaneous.

C. Hrxn= 84 kJ , Srxn= 144 J/K , T= 300 K

Express your answer using two significant figures.

Suniv =

Predict whether or not the reaction will be spontaneous.

D. Hrxn= 84 kJ , Srxn= 144 J/K , T= 406 K

Express your answer using two significant figures.

Suniv =

Predict whether or not the reaction will be spontaneous.

Explanation / Answer

A.)

System is the reaction so Srxn = Ssys = 144 J/K

S surroundings = - Hrxn/T

    = - 84000 / 300K

= - 280 J/K

Suniv = Sys + Surroundings

             = 144 + (-280)

             = - 1.4 x 10^2 J/K

G = H- T S

       = 84 - 300 x (144 x 10^-3)

        = 40.5 kJ

this reaction is not spontaneous. because G is positive.

B) Hrxn= 84 kJ , Srxn= 144 J/K , T= 751 K

Suniv = Sys + Surroundings

             = 144 + (- 84000 / 751)

             = 32 J/K

G = H- T S

       = 84 - 751 x (144 x 10^-3)

        = -24.144 kJ

this is sponteneous because delta G is negative

Note : similarily you can calculate rest of those.

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