Question

Given the values of ΔH∘rxn, ΔS∘rxn, and T below, determine ΔSuniv.

Part A

ΔH∘rxn=− 89 kJ , ΔSrxn=− 150 J/K , T= 310 K

Express your answer using two significant figures.

Part B

ΔH∘rxn=− 89 kJ , ΔSrxn=− 150 J/K , T= 758 K

Express your answer using one significant figure.

Part C

ΔH∘rxn=+ 89 kJ , ΔSrxn=− 150 J/K , T= 310 K

Express your answer using two significant figures.

Part D

ΔH∘rxn=− 89 kJ , ΔSrxn=+ 150 J/K , T= 403 K

Express your answer using two significant figures.

Answer 1

ΔSsurroundings = -ΔH∘rx/T

ΔSuniv = ΔSsys + ΔSsurr

ΔSsys = ΔSrxn

Part A

ΔSsys = - 150 J/K

ΔSsurr = 89 x 10^3 / 310 = 287 J/K

ΔSuniv = - 150 + 287 = 137 J/K

ΔSuniv = 140 J/K

Part B

ΔSsys = - 150 J/K

ΔSsurr = 89 x 10^3 / 758 = 117.4 J/K

ΔSuniv = - 30 J/K

Part C

ΔSsys = - 150 J/K

ΔSsurr = - 89 x 10^3 / 310 = - 287 J/K

ΔSuniv = - 440 J/K

Part D

ΔH∘rxn=− 89 kJ , ΔSrxn=+ 150 J/K , T= 403 K

ΔSsys = 150 J/K

ΔSsurr =   89 x 10^3 / 403 = 221 J/K

ΔSuniv = 370 J/K

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