Question

± Free Energy and Chemical Equilibrium

The equilibrium constant of a system, *K*, can be related
to the standard free energy change, Δ*G*, using the
following equation:

Δ*G*∘=−*R**T*ln*K*

where *T* is standard temperature in kelvins and
*R* is equal to 8.314 J/(K⋅mol).

Under conditions other than standard state, the following equation applies:

Δ*G*=Δ*G*∘+*R**T*ln*Q*

In this equation, *Q* is the reaction quotient and is
defined the same manner as *K* except that the
concentrations or pressures used are not necessarily the
equilibrium values.

Part A)

At 25 ∘C the reaction from Part A has a composition as shown in the table below.

Substance | Pressure (atm) |

C2H2(g) | 5.35 |

H2(g) | 4.85 |

C2H6(g) | 3.25×10^{−2} |

What is the free energy change, Δ*G*, in kilojoules for
the reaction under these conditions?

Express your answer numerically in kilojoules.

Answer #1

C2H2 + 2H2 -----------------> C2H6

4.75 3.45 4.25 x 10^-2

Qp = P_{C2H6} / P_{C2H2}
P_{H2}^{2}

= 3.25 x 10^-2 / (5.35) (4.85)^2

= 2.58 x 10^-4

R = 8.314 x 10^-3 kJ/ K mol

T = 273 + 25 = 298 K

G = Go + RT lnQp

G = Go + 2.303 RT log Qp

= -241.9 + 2.303 x 8.314 x 10^-3 x 298 x log (2.58 x 10^-4)

=-241.9 -20.47 kJ

= -262.37 kJ

**G = -262.4
kJ**

The equilibrium constant of a system, K, can be related
to the standard free energy change, ΔG∘, using the
following equation:
ΔG∘=−RTlnK
where T is a specified temperature in kelvins (usually
298 K) and R is equal to 8.314 J/(K⋅mol).
Under conditions other than standard state, the following
equation applies:
ΔG=ΔG∘+RTlnQ
In this equation, Q is the reaction quotient and is
defined the same manner as K except that the
concentrations or pressures used are not necessarily the
equilibrium values....

The equilibrium constant of a system, K, can be related
to the standard free energy change, ΔG∘, using the
following equation:
ΔG∘=−RTlnK
where T is a specified temperature in kelvins (usually
298 K) and R is equal to 8.314 J/(K⋅mol).
Under conditions other than standard state, the following
equation applies:
ΔG=ΔG∘+RTlnQ
In this equation, Q is the reaction quotient and is
defined the same manner as K except that the
concentrations or pressures used are not necessarily the
equilibrium values....

Item 5
The equilibrium constant of a system, K, can be related
to the standard free energy change, ΔG, using the
following equation:
ΔG∘=−RTlnK
where T is standard temperature in kelvins and
R is the gas constant.
Under conditions other than standard state, the following
equation applies:
ΔG=ΔG∘+RTlnQ
In this equation, Q is the reaction quotient and is
defined the same manner as K except that the
concentrations or pressures used are not necessarily the
equilibrium values.
Part A
Acetylene,...

In Part A, we saw that ΔG∘=−242.1 kJ for the
hydrogenation of acetylene under standard conditions (all pressures
equal to 1 atm and the common reference temperature 298 K). In Part
B, you will determine the ΔG for the reaction under a
given set of nonstandard conditions.
At 25 ∘C the reaction from Part A has a composition as shown in
the table below.
Substance
Pressure
(atm)
C2H2(g)
5.35
H2(g)
3.95
C2H6(g)
4.25×10−2
What is the free energy change, ΔG,...

� 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...

he thermodynamic properties for a reaction are related by the
equation that defines the standard free energy, ΔG∘, in
kJ/mol:
ΔG∘=ΔH∘−TΔS∘
where ΔH∘ is the standard enthalpy change in kJ/mol and
ΔS∘ is the standard entropy change in J/(mol⋅K). A good
approximation of the free energy change at other temperatures,
ΔGT, can also be obtained by utilizing this
equation and assuming enthalpy (ΔH∘) and entropy
(ΔS∘) change little with temperature.
Part A
For the reaction of oxygen and nitrogen to...

In Part A, we saw that ΔG∘=−242.1 kJ for the
hydrogenation of acetylene under standard conditions (all pressures
equal to 1 atm and the common reference temperature 298 K). In Part
B, you will determine the ΔG for the reaction under a
given set of nonstandard conditions.
Part B
At 25 ∘C the reaction from Part A has a composition as shown in
the table below.
Substance
Pressure
(atm)
C2H2(g)
3.95
H2(g)
5.65
C2H6(g)
5.25×10−2
What is the free energy...

Part B
At 25 ?C the reaction from Part A has a composition as shown in
the table below.
Substance/Pressure (atM):
C2H2(g) / 4.05
H2(g) / 5.55
C2H6(g) / 5.25×10?2
What is the free energy change, ?G, in kilojoules for the
reaction under these conditions? Express your answer numerically in
kilojoules.

For chemical reactions involving ideal gases, the equilibrium
constant K can be expressed either in terms of the concentrations
of the gases (in M) or as a function of the partial pressures of
the gases (in atmospheres). In the latter case, the equilibrium
constant is denoted as Kp to distinguish it from the
concentration-based equilibrium constant K.
Part A
For the reaction
2CH4(g)⇌C2H2(g)+3H2(g)
K = 0.155 at 1635 ∘C . What is Kp for the
reaction at this temperature?
Express...

For chemical reactions involving ideal gases, the equilibrium
constant K can be expressed either in terms of the concentrations
of the gases (in M) or as a function of the partial pressures of
the gases (in atmospheres). In the latter case, the equilibrium
constant is denoted as Kp to distinguish it from the
concentration-based equilibrium constant K.'
Part A
For the reaction
2CH4(g)⇌C2H2(g)+3H2(g)
K = 0.130 at 1668 ∘C . What is Kp for the
reaction at this temperature?
Express...

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