The change in Gibbs free energy is the amount of energy available to do what? pe

Question

The change in Gibbs free energy is the amount of energy available to do what? perform work drive the reaction in a forward direction change the entropy of the surroundings heat the surroundings Calculate E for the following reaction at 298 K when [Mg^2+] = 0.400 M and [Na^+] = 0.0100 M: Mg^2+ (aq) + 2 Na (s) rightarrow Mg (s) + 2 Na^+ (aq) +0.404 V +0.357 V +1.203 V -0.722 V +0.309 V Can a voltaic cell in which both half-reactions are the same generate a current? Yes, electrons always flow toward the electrode with the more positive standard reduction potential. No, if there is no difference in standard cell potential between the half-reactions, there can be no driving force for electrons to flow. Yes, if there is a difference in concentration between the two half-reactions. Yes, as long as any two half-cells are connected by a salt bridge, a current will now.

Explanation / Answer

Q20. Gibbs free energy is the amount of energy available for a system to do useful work.

Gibbs free energy of system depends on change in enthalpy and entropy at constant T and pressure (dG = dH-TdS)

Q21. Mg^2+ + 2Na -----> 2Na^+ + Mg

The EMF of a cell can be calculated using Nernst equation Ecell = E0cell-(0.0591/n)log[P]/[R]

E0cell = E(Mg^2+/Mg) + Eanode (Na/Na+)

E0cell = -2.714+(-2.363) = 0.351

Ecell = 0.351+(0.0591/2)log((0.010)^2/0.4)

Ecell = 0.404 eV

Q22. No, if there is no potential difference in standard cell potential between the half reactions there is no driving force for the flow of electrons

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