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Chrome File Edit View History Bookmarks People Window Help Go A O 11% D Wed Apr 19 8:57 PM kaycee rae QA E Mastering Chemistry: CH 18 HW TO DO FOI Make pat Secure https Session masteringchemistry.com 7705191 &offset; prev Register CHM 2046 Sp'17 Help Close Applic files and close CH 18 HW Exercise 18.72 with feedback Resources previous l 3 of 7 l next Exercise 18.72 with feedback Part A calculate AG Exza and E eel at 25°C for a redox Express your answer using two significant figures. reaction with m 4 that has an equilibrium constant of K 4.0x10 AG 8.0 kJ You may want to reference Submi My Answers Give Up (DA ages 877- 881) section 18.5 while completing this problem. Correct The standard free energy is important when determining the spontaneity of a reaction. Given the equilibrium constant, the standard free energy of the reaction can be calculated using the following equation: RT rocn 8.314 x 298 K x ln (4.0 x 10-2) x K-mol 1000J 8.0kJ AG, n for this reaction is positive. Therefore, the reaction is nonspontaneous in the forward direction. Part B Express your answer using two significant figures. ADI SUI Submit My Answers Give Up incorrect; Try Again; 3 attempts remaining

Explanation / Answer

A)

T = 25.0 oC =(25.0+273)K = 298.0 K

use:

delta G = -R*T*ln Kc

= - 8.314*298.0* ln(4.0*10^-2)

= 7975 J/mol

= 8.0 KJ/mol

Answer: 8.0 KJ/mol

B)

E = (2.303*R*T)/(n*F) log Kc

At 25 oC or 298 K, 2.303*R*T/F = 0.059

So, E = (0.059/n)*log Kc

E = (0.059/4)*log (4.0*10^-2)

E = -0.021 V

Answer: -0.021 V

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