If you calculate a value for ∆ G ° for a reaction using the values of Δ G f ∘ in Appendix 4 and get a negative number, is it correct to say that the reaction is always spontaneous? Why or why not? Free energy changes also depend on concentration. For gases, how is G related to the pressure of the gas? What are standard pressures for gases and standard concentrations for solutes? How do you calculate ∆ G for a reaction at nonstandard conditions? The equation to determine ∆G at nonstandard conditions has Q in it: What is Q ? A reaction is spontaneous as long as ∆ G is negative; that is, reactions always proceed as long as the products have a lower free energy than the reactants. What is so special about equilibrium? Why don’t reactions move away from equilibrium?
If you calculate a value for ∆ G ° for a reaction using the values of Δ G f ∘ in Appendix 4 and get a negative number, is it correct to say that the reaction is always spontaneous? Why or why not? Free energy changes also depend on concentration. For gases, how is G related to the pressure of the gas? What are standard pressures for gases and standard concentrations for solutes? How do you calculate ∆ G for a reaction at nonstandard conditions? The equation to determine ∆G at nonstandard conditions has Q in it: What is Q ? A reaction is spontaneous as long as ∆ G is negative; that is, reactions always proceed as long as the products have a lower free energy than the reactants. What is so special about equilibrium? Why don’t reactions move away from equilibrium?
If you calculate a value for ∆G° for a reaction using the values of
Δ
G
f
∘
in Appendix 4 and get a negative number, is it correct to say that the reaction is always spontaneous? Why or why not? Free energy changes also depend on concentration. For gases, how is G related to the pressure of the gas? What are standard pressures for gases and standard concentrations for solutes? How do you calculate ∆G for a reaction at nonstandard conditions? The equation to determine ∆G at nonstandard conditions has Q in it: What is Q? A reaction is spontaneous as long as ∆G is negative; that is, reactions always proceed as long as the products have a lower free energy than the reactants. What is so special about equilibrium? Why don’t reactions move away from equilibrium?
(c) The following data have been obtained for the hydrolysis of sucrose, C12H22O11, to
glucose, C6H12O6, and fructose C6H12O6, in acidic solution:
C12H22O11 + H2O → C6H12O6 + C6H12O6
[sucrose]/mol dm³
t/min
0
0.316
14
0.300
39
0.274
60
0.256
80
0.238
110
0.211
(i) Graphically prove the order of the reaction and determine the rate constant of the
reaction.
(ii) Determine the half-life, t½ for the hydrolysis of sucrose.
(III) adsorbent
(b) Adsorption of the hexacyanoferrate (III) ion, [Fe(CN)6] ³, on y-Al2O3 from aqueous
solution was examined. The adsorption was modelled using a modified Langmuir
isotherm, yielding the following values of Kat pH = 6.5:
(ii)
T/K
10-10 K
280
2.505
295
1.819
310
1.364
325
1.050
Determine the enthalpy of adsorption, AadsHⓇ.
If the reported value of entropy of adsorption, Aads Se = 146 J K-1 mol-1 under the above
conditions, determine Aads Gº.
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