In thermodynamics, we determine the spontaneity of a reaction by the sign of G.

Question

In thermodynamics, we determine the spontaneity of a reaction by the sign of G. In electrochemistry, spontaneity is determined by the sign of Ecell. The values of G and Ecell are related by the following formula: G=nFEcell where n is the number of moles of electrons transferred and F=96,500J/Vmol e is the Faraday constant.

Part A The standard reduction potentials of lithium metal and chlorine gas are as follows: Reaction, Reduction potential (V) Li+(aq)+eLi(s) 3.04

Cl2(g)+2e2Cl(aq) +1.36

In a galvanic cell, the two half-reactions combine to 2Li(s)+Cl2(g)2Li+(aq)+2Cl(aq) Calculate the cell potential of this reaction under standard reaction conditions. Express your answer with the appropriate units.

Part B: Calculate the free energy G of the reaction. Express your answer with the appropriate units.

Part C:

What can be said about the spontaneity of this reaction?

The reaction is:

a. spontaneous as written. b. spontaneous in the reverse direction. c. at equilibrium. d. nonspontaneous in either direction.

Explanation / Answer

Part A

E0cell = E0cathode - E0anode = 1.36 - ( - 3.04 ) = 4.40 V

Part B

G=nFEcell = - 2 * 96500 * 4.40 = - 849200 J

Part C

(a) Spontaneous as written

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