Calculations for ΔG and KeqΔG=-NFECELL=-296.4850.45=-86836.5ΔG=-RTlnKEQ-86836.5=-8.3144293lnKEQlnKEQ=-86836.5-2436.1192lnKEQ=34.65e34.65=KEQKEQ=3.545
Based on the numerical value for Ecell (measured), the reaction is spontaneous. Being that the redox reaction has a positive value for Ecell, the reaction is spontaneous. It would cease to be spontaneous if the Ecell value is negative (Aus-e-tute, p.1).
Based on the numerical value for delta G (calculated), the reaction is spontaneous. Delta G, or Gibbs free energy can have a positive, negative or null value. A reaction is non spontaneous when delta G is positive, and spontaneous when the value is negative. A reaction is said to be at equilibrium when delta G has the null (zero) value.
Based on the numerical value for Keq (calculated), the products are favored. The Keq numerical value is positive, meaning that the forward reaction is spontaneous, and the reactants shall be depleted in favor of the products (Tamu, p. 1).
Based on observations made in the laboratory, the reaction is spontaneous. Spontaneous reactions require no addition of catalysts or changes in temperature or pressure for them to proceed, and this reaction did not require a catalyst or a change in temperature or pressure.
Half cell equations:Oxidation:Fe→Fe2++2e-
Standard reduction potential at 250C: -0.41v
Reduction: Cu2+ + 2e-→Cu
Standard reduction potential at 250C: +0.34v
Overall redox reaction: Fe+Cu2+→Fe2++Cu
Calculated E0cellusinf standard reduction potentials:-0.41+0.34=-0.07v
Effects of temperature on cell potential:
ΔS determined from slope of ΔG vs. Temp. (Kelvin) = ΔyΔx =-86836.5-(-125430.5)295-308
=38594-13
= -2968.8K-1
ΔH(calculated):
This is obtained from the intercept of the graph when ΔG is zero as follows.
y=mx+c
Where y = -86836.5
m=-2968.8
x=295
c=y-mx
c=-86836.5—2968.8×295
= 788959.5
Therefore, when y=0, x is obtained as follows:
0=mx+c
mx=-c
x=-cm = -788959.5/-2968.8 = 265.75K
Works Cited
Aus-e-tute. "Spontaneous and non-spontaneous redox reactions." 2016. Aus-e-tute. 10 Aug 2016 <http://www.ausetute.com.au/redoxspon.html>.
Tamu. "Thermodynamics: Gibbs Free Energy." 2016. Tamu. 10 Aug 2016 <https://www.chem.tamu.edu/class/majors/tutorialnotefiles/gibbs.htm>.
