Question

Given the following information, calculate the standard Gibbs free energy of the reaction at 1455 K. State if the reaction is spontaneous or nonspontaneous followed by the temperature at which the reaction switches spontaneity if applicable.

CaCO_{3}(s) --> CaO(s) + CO_{2}(g)

Given: Δ°H = 179.2 kJ , Δ°S = 160.2 J/K

Answer #1

1)

deltaHo = 179.2 KJ/mol

deltaSo = 160.2 J/mol.K

= 0.1602 KJ/mol.K

T = 1455 K

we have below equation to be used:

deltaGo = deltaHo - T*deltaSo

deltaGo = 179.2 - 1455.0 * 0.1602

deltaGo = -53.891 KJ/mol

since delta Go is negative, the reaction is spontaneous

Answer: -53.891 KJ/mol, spontaneous

2)

deltaHo = 179.2 KJ/mol

deltaSo = 160.2 J/mol.K

= 0.1602 KJ/mol.K

we have below equation to be used:

deltaGo = deltaHo - T*deltaSo

for reaction to be spontaneous, deltaGo should be negative

that is deltaGo<0

since deltaGo = deltaHo - T*deltaSo

so, deltaHo - T*deltaSo < 0

179.2- T * 0.1602 < 0

T * 0.1602 > 179.2

T > 1119 K

Answer: 1119 K

± Gibbs Free Energy: Temperature Dependence Gibbs free energy
(G) is a measure of the spontaneity of a chemical reaction. It is
the chemical potential for a reaction, and is minimized at
equilibrium. It is defined as G=H−TS where H is enthalpy, T is
temperature, and S is entropy.
The chemical reaction that causes aluminum to corrode in air is
given by
4Al+3O2→2Al2O3
in which at 298 K
ΔH∘rxn
= −3352 kJ
ΔS∘rxn
= −625.1 J/K
Part A
What is...

A. Using given data, calculate the change in
Gibbs free energy for each of the following reactions. In each case
indicate whether the reaction is spontaneous at 298K under standard
conditions.
2H2O2(l)→2H2O(l)+O2(g)
Gibbs free energy for H2O2(l) is -120.4kJ/mol
Gibbs free energy for H2O(l) is -237.13kJ/mol
B. A certain reaction has ΔH∘ = + 35.4
kJ and ΔS∘ = 85.0 J/K . Calculate ΔG∘ for the
reaction at 298 K. Is the reaction spontaneous at
298K under standard
conditions?

Calculate the change in Gibbs free energy for each of the
following sets of ?H?rxn, ?S?rxn, and T.
Part A ?H?rxn=? 115 kJ ; ?S?rxn= 248 J/K ; T= 295 K
Part B ?H?rxn= 115 kJ ; ?S?rxn=? 248 J/K ; T= 295 K
Part C ?H?rxn=? 115 kJ ; ?S?rxn=? 248 J/K ; T= 295 K Express
your answer using two significant figures.
Part D ?H?rxn=? 115 kJ ; ?S?rxn=? 248 J/K ; T= 565 K Express
your answer...

So I had to calculate the Gibbs Free energy for all the
reactions:
Ca(s)+CO2(g)+12O2(g)→CaCO3(s) =
ΔG∘ = -734 kJ
CaCO3(s)→CaO(s)+CO2(g) = 131 kJ
CO(g)+H2O(g)→H2(g)+CO2(g) =
-28.6 KJ
but now I have to predict what lowering the temeprature will do
to Gibbs Free Energy:
it will decrease with decreasing temp.
ΔG∘ will increase with decreasing temperature.
ΔG∘ will change slightly with decreasing
temperature.

� Gibbs Free Energy: Equilibrium Constant
Nitric oxide, NO, also known as nitrogen monoxide, is one of the
primary contributors to air pollution, acid rain, and the depletion
of the ozone layer. The reaction of oxygen and nitrogen to form
nitric oxide in an automobile engine is
N2(g)+O2(g)?2NO(g)
The spontaneity of a reaction can be determined from the free
energy change for the reaction, ?G?.
A reaction is spontaneous when the free energy change is less
than zero.
A reaction...

1) Given the following thermochemical reaction and thermodynamic
data, find Gibbs Free Energy, ΔG, and determine if the reaction is
spontaneous or non-spontaneous at 25 °C?
N2(g) + 3H2(g) → 2NH3(g) ΔH = -91.8 kJ
ΔS[N2] = 191 J / mol · K, ΔS[H2] = 131 J / mol · K, and ΔS[NH3]
= 193 J / mol · K
a.98.3 kJ; Non-Spontaneous
b.-98.3 kJ; Spontaneous
c.32.7 kJ; Non-Spontaneous
d.ΔG = -32.7 kJ; Spontaneous
2) What is the oxidation number...

The chemical reaction that causes iron to corrode in air is
given by
4Fe+3O2→2Fe2O3
in which at 298 K
ΔH∘rxn
= −1684 kJ
ΔS∘rxn
= −543.7 J/K
Gibbs free energy (G) is a measure of the spontaneity of a
chemical reaction. It is the chemical potential for a reaction, and
is minimized at equilibrium. It is defined as G=H−TS where H is
enthalpy, T is temperature, and S is entropy.
Part A
What is the standard Gibbs free energy for...

Consider the following reaction: CaCO3(s)→CaO(s)+CO2(g).
Estimate ΔG for this reaction at each of the following
temperatures. (Assume that ΔH∘ and ΔS∘ do not change too much
within the given temperature range). Also determine whether the
reactions in part 1 and 2 are spontaneous or nonspontaneous.
1).1095 K 2).1500K

Diamond
a. At 298 K, what is the Gibbs free energy change G for the
following reaction? Cgraphite -> Cdiamond
b. Is the diamond thermodynamically stable relative to graphite
at 298 K?
c. What is the change of Gibbs free energy of diamond when it is
compressed isothermally from 1 atm to 1000 atm at 298 K?
d. Assuming that graphite and diamond are incompressible,
calculate the pressure at which the two exist in equilibrium at 298
K.
e....

1.
Calculate the standard free energy change at 500 K for the
following reaction.
Cu(s) +
H2O(g) à CuO(s) +
H2(g)
ΔH˚f
(kJ/mol)
S˚
(J/mol·K)
Cu(s)
0
33.3
H2O(g)
-241.8
188.7
CuO(s)
-155.2
43.5
H2(g)
0
130.6
2. When
solid ammonium nitrate dissolves in water, the resulting solution
becomes cold. Which is true and why?
a. ΔH˚
is positive and ΔS˚ is positive
b. ΔH˚
is positive and ΔS˚...

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