Homogenous Chemical Equilibrium
HOMOGENOUS CHEMICAL
EQUILIBRUM
Homogenous equilibrium is an
equilibrium in which the reactants
and the products are in the same
phase.
-Homogenous gaseous equilibria
Case I:
The Hydrogen-Iodide system
Consider a reaction
A +B
2C
e.g
+
t=0
a
b
t=t
a-x
b-x
2x
if V (in dm
3
) is the total volume of
the reaction mixture
then,
Hence,
=
is independent of the volume
In term of partial pressure,
But
, and
Where
total number of moles,
total (external) pressures
are partial
pressures of A, B and C respectively.
Examples:
A mixture of 1 mole of H
2
and 1 mole
of I
2
in a flask was heated until the
equilibrium is reached. On analysis,
the equilibrium mixture is found to
contain 0.7mole of HI. Calculate the
K
c
Consider this reaction
+
Given that the partial pressures of the
following substances at 45
o
C are =
0.065atm, =0.45 atm. and =0.245
atm. Calculate (a) the equilibrium
constant K
p
for the reaction at 45
o
C
(b) the equilibrium constant K
p
for
the backward reaction
K
c
for this reaction +
The K
p
for this equilibrium reaction:
+
is 0.11 at 25
o
C, calculate Kc at
this temperature.
The following results were obtained during analysis of a
reaction
+
At 25
o
C and 4 atm., is 10% dissociated, calculate the
Kp
for this reaction,
+
N
2
O
4
at 1 atm and 25
o
C dissociated
by 18.5%, calculate its K
p
at this
temperature. If the atmospheric
temperature was reduced to half its
original value at the same
temperature, calculate the degree of
dissociation of the gas.
N
2
O
4
is 25% dissociated at 30
o
C and
1 atm., calculate
The equilibrium constant for the
decomposition
The amount of NO
2
that would be
attained if there had been 4 moles of
N
2
O
4
at the same temperature and
pressure.
N
2
O
4
is 25% dissociated at 37
0
C and
1 atm., calculate
The K
p
and (ii) the % dissociation at
0.1 atm and 37
o
C
An equilibrium mixture at 27
o
C
contains N
2
O
4
and NO
2
having 0.28
atm. and 1.1 atm. pressures
respectively. If the volume of the
container is doubled, calculate the
new equilibrium pressure of the
gases.
In an experiment, H
2
and N
2
in the
mole ratio 3:1 produced 0.0735mole
fraction of NH
3
at 350
o
C and total
pressure of 1013KNm
-2
. Calculate Kp
for the forward and reverse reactions
The K
p
for this equilibrium reaction
N
2 (g)
+ 3H
2 (g)
2NH
3 (g)
is
1.45 x 10
-5
at 500
o
C. Calculate the
partial pressure of NH
3
when the
partial pressure of H
2
is 0.928atm
and that of N
2
is 0.432atm.
The dissociation pressure of CaCO
3
is
342mmHg at 840
o
C and at 860
o
C,
the dissociation pressure is
420mmHg. Calculate the heat of
dissociation of the carbonate. Given
that R=8.314KJmol
-1
.
consider this reaction
N
2 (g)
+ 3H
2 (g)
2NH
3 (g)
,
The K
p
is 1.64x10
-4
at 400
o
C.
calculate (i) the ∆G of the reaction
(ii) ∆G when the partial pressure
of N
2
, H
2
and NH
3
are 10atm, 30
atm and 3 atm respectively.
In an esterification process
between 1 mole of ethanoic acid
and 1 mole of ethanol at 25
o
C,
66.7% of the acid is esterified
calculate the equilibrium
constant and ∆G
o
.
When 1 mole of ethanoic acid and
1 mole of ethanol were heated
together at a temperature of 25
o
C
until the equilibrium is reached.
Titration of the reaction mixture
shows that 2/3 of the acid have
been used up. Calculate the
equilibrium constant.
CaCO
3(s)
CaO
(s)
+CO
2(g)
2H
2
O
(l)
2H
2(g)
+
O
2(g)
NH
4
Cl
(s)
NH
3(g)
+
HCl
(g)
Homogenous chemical equilibrium occurs when reactants and products are in the same phase. This equilibrium remains independent of the volume of the reaction mixture. The concept is illustrated through the example of the Hydrogen-Iodide system and a generic reaction A + B --> 2C. Partial pressure plays a crucial role in understanding this equilibrium state.
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Presentation Transcript
HOMOGENOUS CHEMICAL HOMOGENOUS CHEMICAL EQUILIBRUM EQUILIBRUM
Homogenous equilibrium is an Homogenous equilibrium is an equilibrium in which the reactants equilibrium in which the reactants and the products are in the same and the products are in the same phase. phase.
- -Homogenous gaseous equilibria Homogenous gaseous equilibria
Case I: Case I: The Hydrogen The Hydrogen- -Iodide system Iodide system
Consider a reaction Consider a reaction
A +B A +B 2C 2C
e.g e.g + +
t=0 t=0 a a b b
t=t t=t a a- -x x b b- -x x 2x 2x
if V (in dm if V (in dm3 3) is the total volume of ) is the total volume of the reaction mixture the reaction mixture
then, then,
Hence, Hence, = =
is independent of the volume is independent of the volume
In term of partial pressure, In term of partial pressure,
But But , and , and
Where Where total number of moles, total number of moles,
total (external) pressures total (external) pressures are partial pressures of A, B and C respectively. pressures of A, B and C respectively. are partial
Examples: Examples:
of I of I2 2in a flask was heated until the in a flask was heated until the equilibrium is reached. On analysis, equilibrium is reached. On analysis, the equilibrium mixture is found to the equilibrium mixture is found to contain 0.7mole of HI. Calculate the contain 0.7mole of HI. Calculate the K Kc c
Consider this reaction Consider this reaction + +
following substances at 45 following substances at 45 0.065atm, =0.45 atm. and =0.245 0.065atm, =0.45 atm. and =0.245 atm. Calculate (a) the equilibrium atm. Calculate (a) the equilibrium constant K constant Kp pfor the reaction at 45 for the reaction at 45o oC C (b) the equilibrium constant K (b) the equilibrium constant Kp pfor the backward reaction the backward reaction for
K Kc cfor this reaction + for this reaction +
The K The Kp pfor this equilibrium reaction: for this equilibrium reaction:
is 0.11 at 25o oC, calculate Kc at C, calculate Kc at + + is 0.11 at 25 this temperature. this temperature.
The following results were obtained during analysis of a The following results were obtained during analysis of a reaction reaction + +
At 25o oC and 4 atm., is 10% dissociated, calculate the C and 4 atm., is 10% dissociated, calculate the Kp Kp for this reaction, for this reaction, At 25 + +
by 18.5%, calculate its K by 18.5%, calculate its Kp p temperature. If the atmospheric temperature. If the atmospheric temperature was reduced to half its temperature was reduced to half its original value at the same original value at the same temperature, calculate the degree of temperature, calculate the degree of dissociation of the gas. dissociation of the gas.
N N2 2O O4 4is 25% dissociated at 30 is 25% dissociated at 30o oC and 1 atm., calculate 1 atm., calculate C and
The equilibrium constant for the The equilibrium constant for the decomposition decomposition
The amount of NO The amount of NO2 2that would be attained if there had been 4 moles of attained if there had been 4 moles of N N2 2O O4 4at the same temperature and at the same temperature and pressure. pressure. that would be
N N2 2O O4 4is 25% dissociated at 37 is 25% dissociated at 370 0C and 1 atm., calculate 1 atm., calculate C and
The K The Kp pand (ii) the % dissociation at and (ii) the % dissociation at 0.1 atm and 37 0.1 atm and 37o oC C
having 0.28 having 0.28 atm. and 1.1 atm. pressures atm. and 1.1 atm. pressures respectively. If the volume of the respectively. If the volume of the container is doubled, calculate the container is doubled, calculate the new equilibrium pressure of the new equilibrium pressure of the gases. gases.
In an experiment, H In an experiment, H mole ratio 3:1 produced 0.0735mole mole ratio 3:1 produced 0.0735mole fraction of NH fraction of NH3 3at 350 at 350o oC and total pressure of 1013KNm pressure of 1013KNm- -2 2. Calculate Kp for the forward and reverse reactions for the forward and reverse reactions C and total . Calculate Kp
The K The Kp pfor this equilibrium reaction for this equilibrium reaction
2 (g) 2 (g) 1.45 x 10 1.45 x 10- -5 5at 500 partial pressure of NH partial pressure of NH3 3when the partial pressure of H partial pressure of H2 2is 0.928atm and that of N and that of N2 2is 0.432atm. 2 (g) 2 (g) at 500o oC. Calculate the C. Calculate the 3 (g) 3 (g) when the is 0.928atm is 0.432atm.
342mmHg at 840 342mmHg at 840o oC and at 860 the dissociation pressure is the dissociation pressure is 420mmHg. Calculate the heat of 420mmHg. Calculate the heat of dissociation of the carbonate. Given dissociation of the carbonate. Given that R=8.314KJmol that R=8.314KJmol- -1 1. . C and at 860o oC, C,
consider this reaction consider this reaction
N N2 (g) 2 (g) + 3H + 3H2 (g) 2NH 2NH3 (g) 3 (g), , 2 (g)
p p calculate (i) the G of the reaction calculate (i) the G of the reaction (ii) G when the partial pressure (ii) G when the partial pressure of N of N2 2, H , H2 2and NH and NH3 3are 10atm, 30 atm and 3 atm respectively. atm and 3 atm respectively. are 10atm, 30
