CCE – 1
CHEMICAL EQUILIBRIUM
C1
Reaction is set to be equilibrium reaction where the rate of the forward reaction is equal to the rate
of backward reaction. Chemical equilibrium at a given temperature there is a constancy of certain
observable properties such as pressure, concentration and density. Chemical equilibrium can be
approach from another side. A catalyst can hasten the approach of equilibrium but does not alter the
state of equilibrium. Chemical equilibrium is dynamic in nature.
C2A Expression of equilibrium constant Kc and Kp :
Expression of Kc for aA(g) + bB(g)
Kc 
Kp 
[C]c [D]d
[ A]a [B]b
cC(g) + dD(g)
. If any component in solid state or in excess its conc. is 1.
[PD ]d [PC ]c
[PA ]a [PB ]b
, P  partial pressure can be expressed as PA 
nRT
, PA = PTXA
V
XA  mole fraction
PT  Total pressure
C2B
RELATION BETWEEN Kp and Kc
Kp = Kc (RT)n
n = moles of gaseous product - moles of gaseous reactants.
Practice Problems :
1.
A sample of HI (g) is placed in flask at a pressure of 0.2 atm. At equilibrium, the partial pressure of
HI (g) is 0.04 atm. What is Kp for the given equilibrium ?
2HI (g)
2.
H2(g) + I2(g)
One of the reactions that takes place in produceing steel from iron ore is reduction of iron (II) oxide
by the carbon monoxide to give iron metal and CO2.
FeO (s) + CO (g)
Fe (s) + CO2 (g);
Kp = 0.265 atm at 1050 K
What are the equilibrium partial pressures of CO and CO2 at 1050 K if the initial partial pressures
are : pCO = 1.4 atm and p CO2 = 0.80 atm ?
3.
Dihydrogen gas used in Haber’s process is produced by reacting methane from natural gas with
high temperature steam. The first stage of two stage reaction involves the formation of CO and H2.
In second state, CO formed in first stage is reacted with more steam in water gas shift reaction.
CO (g) + H2O (g)
CO2 (g) + H2 (g).
If a reaction vessel at 400 0C is charged with an equimolar mixture of CO and steam such that
p CO  p H 2O  4.0 bar, what will be the partial pressure of H2O at equilibrium ? Kp = 10.1 at 400 0C.
4.
For the reversible reaction, N2(g) + 3H2(g)
2NH3(g) at 5000C, the value of Kp is 1.44 × 10–5
when partial pressure is measured in atmosphere. The corresponding value of K c, with
concentration in mole litre–1, is
(a)
1.44 × 10–5/(0.082 × 500)–2
(b)
1.44 × 10–5/(8.314 × 733)–2
(c)
1.44 × 10–5/(0.082 × 773)2
(d)
1.44 × 10–5/(0.082 × 773)–2
[Answers : (1) 4.0 (2) p CO 2  1.74 atm , p CO  0.46 atm (3) p = 0.96 bar (4) d]
Einstein Classes,
Unit No. 102, 103, Vardhman Ring Road Plaza, Vikas Puri Extn., Outer Ring Road
New Delhi – 110 018, Ph. : 9312629035, 8527112111
CCE – 2
C3
FACTORS AFFECTING EQUILIBRIUM CONSTANT
1.
Methods of representing the equation :
2NH3, Kc, on reversing the reaction new equilibrium constant K C =
N2 + 3H2
2.
1
KC
If a reaction is multiplied by coefficient ‘n’ then K C = (KC)n and if reaction is divided by coefficient
n then K C = (KC)1/n.
3.
 H / RT
Effect of temperature : K eq  A 0 e
, log
K2
H  T2  T1 



K 1 2.303R  T1 T2 
Practice Problems :
1.
Kp for the equilibrium, FeO(s) + CO(g)
Fe(s) + CO2(g) at 10000C is 0.4. If CO(g) at a
pressure of 1 atm and excess FeO(s) are placed in a container at 10000C, the pressures of CO2(g)
when equilibrium is attained is
(a)
2.
3.222 atm
(d)
4.202 atm
1.0
(b)
0.5
(c)
0.25
(d)
0.75
2.55 atm3
(b)
1 atm3
(c)
5 atm3
(d)
9.55 atm3
0.29 atm
(b)
3.5 atm
(c)
0.53 atm
(d)
1.87 atm
For the reaction NH 2 COONH 4 (s)
2NH 3 (g) + CO 2 (g). The equilibrium constant
–5
3
Kp = 2.9 × 10 atm . The total pressure of gases at equilibrium when 1.0 mole of reactant was heated
will be
(a)
6.
(c)
The equilibrium constant for the reaction 2SO2 + O2
2SO3 at 1000K is 3.5. What would the
partial pressure of oxygen gas have to be to give equal moles of SO2 and SO3?
(a)
5.
2.745 atm
When S in the form of S8 is heated at 900 K, the initial pressure of 1 atmosphere falls by 29% at
equilibrium. This is because of the conversion of some gaseous S8 to gaseous S2. The KP for the
reaction is
(a)
4.
(b)
One mole of hydrogen iodide is heated in a closed container of 2 litre. At equilibrium half mole of
hydrogen iodide has dissociated. The equilibrium constant is
(a)
3.
0.714 atm
0.0194 atm
(b)
0.0388 atm
(c)
0.0580 atm
(d)
0.0667 atm
For the reaction N2O4(g)
2NO2(g), the relation connecting the degree of dissociation () of
N2O4(g) with equilibrium constant Kp is
Kp / p
(a)

(c)
 Kp / P 


 4  Kp / P 


Einstein Classes,
4  Kp / p
Kp
(b)

(d)
 Kp / P 


 4  Kp 


1/ 2
4  Kp
1/ 2
Unit No. 102, 103, Vardhman Ring Road Plaza, Vikas Puri Extn., Outer Ring Road
New Delhi – 110 018, Ph. : 9312629035, 8527112111
CCE – 3
7.
At temperature, T, a compound AB2(g) dissociates according to the reaction
2AB2(g)
2AB(g) + B2(g) with a degree of dissociation x, which is small compared with unity..
The expression of Kp, in terms of x and the total pressure, P is
(a)
8.
Px3
2
(b)
Px2
3
Px3
3
(c)
(d)
Px2
2
(d)
K1/K2
If K1 and K2 are the respective equilibrium constants for the two reactions,
XeF6(g) + H2O(g)
XeO4(g) + XeF6(g)
XeOF4(g) + 2HF(g)
XeOF4(g) + XeO3F2(g)
The equilibrium constant for the reaction,
9.
XeO4(g) + 2HF(g)
XeO3F2(g) + H2O(g) is
(a)
(b)
K1 K 2
K1/K22
(c)
K2/K1
Determine KC for the reaction 1/2N2(g) + 1/2O2(g) + 1/2Br2(g)
NOBr(g)
from the following information (at 298 K)
2NO (g)
(a)
10.
K1 = 2.4 × 1030
N2(g) + O2(g);
NO(g) + 1/2Br2(g)
NOBr(g);
6.45 × 10–16
9.03 × 10–16
(b)
For the reaction 2NO2(g) + ½ O2(g)
K2 = 1.4
(c)
3 × 10–8
(d)
1.7 × 10–4
N2O5(g)
if the equilibrium constant is Kp, then the equilibrium constant for the reaction.
2N2O5(g)
(a)
11.
4NO2(g) + O2(g) would be
K P2
(b)
2/KP
(c)
1/KP2
(d)
1/ K P
At 700 K, equilibrium constant for the reaction : H2(g) + I2(g)
2HI(g) is 54.8. If 0.5 mol L–1 of
HI(g) is present at equilibrium at 700 K, what are the concentration of H2(g) and I2(g) assuming that
we initially started with HI (g) and allowed it to reach equilibrium at 700 K.
[Answers : (1) a (2) c (3) a (4) a (5) c (6) c (7) a (8) c (9) b (10) c (11) concentration of H2(g) and I2(g)
is equal to 0.0675 mol L–1]
C4
REACTION QUOTIENT (QC)
It is an expression that has the same form as the equilibrium constant expression, but all
concentration values are not necessarily those at equilibrium.
aA+b B
c C + d D, Q c 
i)
If Qc > Kc, backward reaction takes place
ii)
If Qc < Kc, forward reaction takes place
iii)
If Qc = Kc, the reaction mixture is at equilibrium
Einstein Classes,
[C]c [D]d
[ A]a [B]b
Unit No. 102, 103, Vardhman Ring Road Plaza, Vikas Puri Extn., Outer Ring Road
New Delhi – 110 018, Ph. : 9312629035, 8527112111
CCE – 4
Practice Problems :
1.
A mixture of 1.57 mol of N2, 1.92 mol of H2 and 8.13 mol of NH3 is introduced into a 20 L reaction
vessel at 500 K. At this temperature, the equilibrium constant, Kc for the reaction
2NH3 (g) is 1.7 × 102
N2(g) + 3H2(g)
Is the reaction mixture at equilibrium ? If not, what is the direction of net reaction ?
2.
Ethyl acetate is formed by the reaction between ethanol and acetic acid and the equilibrium is
represented as :
CH3COOH (l) + C2H5OH (l)
3.
CH3COOC2H5 (l) + H2O (l)
(i)
Write the concentration ratio (reaction quotient) Qc, for this reaction. (Note that water is
not in excess and is not a solvent in this reaction).
(ii)
At 293 K, if one starts with 1.00 mol of acetic acid and 0.18 of ethanol, there is 0.171 mol of
ethyl acetate in the final equilibrium mixture. Calculate the equilibrium constant.
(iii)
Starting with 0.5 mol of ethanol and 1.0 mol of acetic acid and maintaining it at 293 K,
0.214 mol of ethyl acetate is found after sometime. Has equilibrium been reached ?
Equilibrium constant, Kc for the reaction,
N2(g) + 3H2(g)
2NH3(g) at 500 K is 0.061.
At a particular time, the analysis shows that composition of the reaction mixture is 3.00 mol L–1 N2,
2.0 mol L–1 H2, and 0.5 mol L–1 NH3. Is the reaction at equilibrium ? If not, in which direction does the
reaction tend to proceed to reach equilibrium ?
4.
At a certain temperature, KC for SO 2( g )  NO 2( g )  SO 3 ( g )  NO ( g ) is 16. If we take one mole of

each of all the four gases in one litre container, what would be the equilibrium concentrations of NO
and NO2 are respectively
(a)
0.6, 0.4
(b)
1.6, 0.6
(c)
1.6, 0.4
(d)
0.4, 0.6
3
[Answers : (1) 2.38 × 10 , As Qc > K c, the net reaction will be in the backward direction
(2) (ii) Kc = 3.919 (iii) Qc = 0.2037 (3) Qc = 0.010, as Qc < Kc the reaction moves in the right hand
direction to reach the equilibrium (4) c]
C5
THERMODYNAMICS OF CHEMICAL EQUILIBRIUM
Spontaneous of natural process is a process that occurs in a system left to itself once started; no
action from outside the system is necessary to make the process continued.
Gibbs Free Energy Change and Spontaneity :
G = H – TS
For a process occuring at constant T and P, if
(i)
G < 0 (negative) the process is spontaneous
(ii)
G > 0 (positive) the process is nonspontaneous
(iii)
G = 0 (zero) the process is at equilibrium
Relation of G0 to the equilibrium constant K :
G0 = –2.303 RT log K
C6
LE-CHATELIER’S PRINCIPLE
It states that “When a system at equilibrium is subjected to some stress (such as a change in
concentration, temperature, pressure) then the equilibrium adjusted itself in such a way so as to
nullify the effects of the stress”. With the help of this principle it is possible to predict favourable
conditions for the reactions.
Einstein Classes,
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New Delhi – 110 018, Ph. : 9312629035, 8527112111
CCE – 5
CONCLUSIONS
i)
If endothermic reaction Keq, T and Keq, T
ii)
In exothermic reaction Keq, T and Keq, T
iii)
If P reaction will move to that side where V i.e. where no. of mole of gaseous components is less.
iv)
If concentration of reactant decreases then reaction takes place in backward reaction.
By chance of conc. pressure, volume, value of Kp and Kc does not change it only changes with
temperature.
Addition of an Inert Gas at Constant Volume of Constant Pressure :
i)
At Constant Volume : The addition of an inert gas at constant volume has no effect. It only increase
the total pressure but does not alter the partial pressure of various species.
ii)
At Constant Pressure : The addition of an inert gas at constant pressure will favour the direction of
reaction where total no. of moles at equilibrium show an increase.
Practice Problems :
1.
2Br at 500 K and 700 K and 1 × 10–10 and
The equilibrium constant for the reaction, Br2
1 × 10–5 respectively. The reaction is
(a)
2.
3.
Endothermic
(b)
Exothermic
For an equilibrium reaction A(g) + B(g)
would cause
(c)
Fast
(d)
Slow
C(g) + D(g), H = +ve, an increase in temperaturee
(a)
an increase in the value of Keq
(b)
a decrease in the value of Keq
(c)
no change in the value of Keq
(d)
a change in Keq which cannot be qualitatively predicated
Given the following reaction at equilibrium N2(g) + 3H2(g)
2NH3(g)
Some inert gas is added at constant volume. Predict which of the following facts will be affected ?
4.
5.
(a)
More of NH3 (g) is produced
(b)
Less of NH3(g) is produced
(c)
No effect on the degree of advancement of the produced reaction at equilibrium
(d)
KP of the reaction is increased.
Predict which of the following facts for the equilibrium reaction 2NH3(g)
holds good ?
N2(g) + 3H2(g)
(a)
KP of the reaction is changed with increase in pressure of the system
(b)
KP of the reaction remains unaffected with increase in pressure of the system
(c)
More of NH3(g) is decreased with increase in pressure
(d)
Less of H2(g) is formed as compared to N2(g)
The oxidation of SO2 by O2 to SO3 is an exothermic reaction. The yield of SO3 will be maximum if
(a)
temperature is increased and pressure is kept constant
(b)
temperature is reduced and pressure is increased
(c)
both temperature and pressure are increased
(d)
both temperature and pressure arereduced
Einstein Classes,
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New Delhi – 110 018, Ph. : 9312629035, 8527112111
CCE – 6
6.
7.
8.
9.
For a chemical reaction 3X(g) + Y(g)
by
(a)
temperature and pressure
(b)
temperature only
(c)
pressure only
(d)
temperature, pressure & catalyst
When NaNO3(s) is heated in a closed vessel, oxygen is liberated and NaNO2(s) is left behind. At
equilibrium
(a)
addition of NaNO2 favours reverse reaction
(b)
addition of NaNO3 favours forward reaction
(c)
increasing temperature favours forward reaction
(d)
increasing pressure favours reverse reaction
For the gas phase reaction C2H4 + H2
C2H6 H = –136.8 kJ mol–1 carried out in a vessel, the
equilibrium concentration of C2H4 can be increased by
(a)
increasing the temperature
(b)
decreasing the pressure
(c)
removing some H2
(d)
all of above
PCl5 is 50% dissociated into PCl3 and Cl2 at 1 atmosphere. It will be 40% dissociated at
(a)
10.
X3Y(g), the amount of X3Y(g) at equilibrium is affected
1.75 atm
(b)
1.84 atm
(c)
2.00 atm
(d)
1.25 atm
5
The equilibrium constant for the following reaction is 1.6 × 10 at 1024 K.
H2(g) + Br2(g)
2HBr(g)
Find the equilibrium pressure of all gases if 10.0 bar of HBr is introduced into a sealed container at
1024 K.
[Answers
:
(1)
a
(2)
a
(3)
c
(4)
b
(5)
b
(6)
a
(7)
c
(8)
d
(9)
2
(10) p H 2  p Br2  2.5  10 bar , p HBr  10.0 bar ]
Einstein Classes,
Unit No. 102, 103, Vardhman Ring Road Plaza, Vikas Puri Extn., Outer Ring Road
New Delhi – 110 018, Ph. : 9312629035, 8527112111
a
CCE – 7
SINGLE CORRECT CHOICE TYPE
1.
2.
The vapour density of undecomposed N2O4 is 46.
When heated, vapour density decreases to 24.5 due
to its dissociation to NO2. The per cent dissociation
of N2O4 at the final temperature is
(a)
87
(b)
60
(c)
40
(d)
70
7.
highest yield of Z at equilibrium occurs at
5.
1000 arm and 500 C
(b)
500 atm and 5000C
(b)
increase the amount of B to double its
value
(c)
increase the amounts of both A and B to
double their values
(d)
cause no change in the amounts of
A and B.
(c)
1000 atm and 100 C
For the reaction 2NO(g)
H = –180 kJ mol–1
(d)
500 atm and 1000C
which of the following facts does not hold good ?
8.
0
N2(g) + O2(g),
(a)
The pressure changes at constant
temperature do not affect the equilibrium
constant
in a closed container and an inert gas, helium is
introduced. Which of the following statements are
correct
(b)
The volume changes at constant
temperature do not affect the equilibrium
constant
(a)
Concentration of SO2, Cl2 and SO2Cl2
change
(c)
The dissociation of NO is favoured more
at high temperature
(b)
More chlorine is formed
(d)
(c)
Concentration of SO2 is reduced
The dissociation of NO is favoured less
at high temperature
(d)
None of these
The equilibrium,
SO2(g) + Cl2(g) is attained at 250C
9.
For the reaction, N2 + 3H2
For the reaction CaCO3(s)
CaO(s) + CO2(g),
the addition of more of CaO(s) causes
2NH3 in a vessel,
(a)
after the addition of equal number of mole of N2
and H2, equilibrium state is formed. Which of the
following is correct.
the decrease in the concentration of
CO2(g)
(b)
the increase in the concentration of
CO2(g)
(a)
[H2] = [N2]
(b)
[H2] < [N2]
(c)
no change in the concentration of CO2(g)
(c)
[H2] > [N2]
(d)
[H2] > [NH3]
(d)
the increase in the concentration of
CaCO3(s)
When two reactants A and B are mixed to give
products C and D, the reaction quotient Q, at the
initial stages of the reaction
(a)
Is zero
(b)
Decreases with time
One mole of N2O4(g) at 300 K is kept in a closed
container under one atmosphere. It is heated to 600
K when 20% of N2O4(g) decomposed to NO2(g). The
resultant pressure is
(c)
Is independent of time
(a)
1.2 atm
(b)
2.4 atm
Increases with time
(c)
2.0 atm
(d)
1.0 atm
(d)
6.
increase the amount of A to double its
value
0
SO2Cl2(g)
4.
(a)
2Z(g); H = –80 kcal the
(a)
A(g) + B(g).
doubling the quantity of AB(s) would
For the reaction,
2X(g) + Y(g)
3.
In a system AB(s)
The concentration of a pure solid or liquid phase is
not included in the expression of equilibrium
constant because
(a)
Solid and liquid concentrations are
independent of their quantities.
(b)
Solids and liquids react slowly
(c)
increase the amounts of both A and B to
double their values
(d)
cause no change in the amounts of
A and B
Einstein Classes,
10.
11.
One mole of N2O(g) is kept in a closed container
along with gold catalyst at 450 K under one
atmosphere. It is heated to 900 K when it
dissociates to N2(g) and O2(g) giving an equilibrium
pressure of 2.4 atm. The degree of dissociation of
N2O(g) is
(a)
20%
(b)
40%
(c)
50%
(d)
60%
Unit No. 102, 103, Vardhman Ring Road Plaza, Vikas Puri Extn., Outer Ring Road
New Delhi – 110 018, Ph. : 9312629035, 8527112111
CCE – 8
12.
13.
In a reversible reaction, study of its mechanism says
that both the forward and backward reaction
follow first order kinetics. If the half life of forward
reaction (t ½) is 400 sec and than of backward
reaction (t½)b is 250 sec. The equilibrium constant
of the reaction is
(a)
any value of temperature and pressure
(b)
lowering of temperature as well as
pressure
(c)
increasing temperature as well as
pressure
(a)
1.6
(b)
0.433
(d)
(c)
0.625
(d)
1.109
lowering the temperature and increasing
the pressure
In a system
A(s)
2B(g) + 3C(g)
If the concentration of C at equilibrium is doubled
at the new equilibrium, it will cause the equilibrium
concentration of B to change to
14.
(a)
two times the original value
(b)
one half of its original value
(c)
22 times its original value
(d)
1/22 times the original value
For the reaction,
CO(g) + Cl2(g)
to
(a)
(c)
15.
16.
COCl2(g), the Kp/Kc is equal
1
RT
RT
(b)
RT
(d)
1
The correct relationship between free energy
change in a reaction and the corresponding equilibrium constant kc is
(a)
G = RT ln Kc
(b)
G = RT ln Kc
(c)
G0 = RT ln Kc
(d)
G0 = RT ln Kc
For the reaction equilibrium
N2O4 (g) 
 2 NO2(g) the concentrations of N2O4
and NO 2 at equilibrium are 4.8 × 10 –2 and
1.2 × 10–2 mol L–1 respectively. The value of Kc for
the reaction is
17.
ANSWERS
(SINGLE CORRECT CHOICE TYPE)
1.
a
11.
b
2.
c
12.
c
3.
d
13.
d
4.
b
14.
a
(a)
3 × 103 mol L–1
(b)
3.3 × 102 mol L–1
(c)
3 × 10–1 mol L–1
(d)
3 × 10–3 mol L–1
5.
a
15.
d
Consider the reaction equilibrium
6.
a
16.
d
7.
d
17.
d
8.
c
9.
c
10.
b
2SO2(g) + O2


2SO3(g) ;
H0 = –198 kJ
On the basis of Le Chatelier’s principle, the
condition favourable for the forward reaction is
Einstein Classes,
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New Delhi – 110 018, Ph. : 9312629035, 8527112111
CCE – 9
EXCERCISE BASED ON NEW PATTERN
COMPREHENSION TYPE
6.
(a)
0.435
0.10 mole each of SO2 and SO3 are mixed in a
2.0 dm3 flask at 300 K. Equilibrium is attained as
(c)
0.235
7.
2SO2(g) + O2(g) = 2 SO3(g)
The equilibrium pressure is 281.68 kPa.
1.
2.
3.
The mole fraction O2 at equilibrium is
(a)
0.1151
(b)
0.2251
(c)
0.3351
(d)
0.4451
8.
The value of Kc is
6.57
(b)
7.57
(c)
8.57
(d)
9.57
The percentage dissociation of SO3 if initially the
flask contained 0.1 mol of SO3 and none of O2 or
SO2 is
(a)
52.7
(b)
62.8
(c)
72.8
(d)
82.8
0.135
(b)
0.3364
(d)
0.1364
The value of Kp is
(a)
0.4364
(c)
0.2364
0
The value of rG for the reaction at 724 K is
(a)
6682.8 J mol–1
(b)
7682.8 J mol–1
(c)
8682.8 J mol–1
(d)
9682.8 J mol–1
(1/2)N2(g) + (3/2)H2(g)
For the reaction
(p)
NH2COONH4(s)
2NH3(g) + CO2(g)
the equilibrium constant
Kp = 2.92 × 10–5 atm3.
The total pressure of the
gaseous products when 1 mol
of reactant is heated, will be
50
(B)
PCl5 is 40% dissociated (q)
when pressure is 2 atm.
It will be 80% dissociated
when pressure is approx.
0.2
(C)
CH3 – CO – CH3(g)
(r)
CH3 – CH3(g) + CO(g)
Initial pressure of CH3COCH3
is 100 mm. When equilibrium
is set up mol fraction of CO(g)
is 1/3 hence Kp is
1.33
(D)
I2 + I–
I3–.
This reaction is set up in (s)
0.0582
aqueous medium. We start
with 1 mol of I2 and 0.5 mol
of I– in 1 L flask. After
equilibrium is reached, excess
of AgNO3 gave 0.25 mol of
yellow ppt. Equilibrium constant
is
The fraction of NH3 dissociated at a total pressure
p is given by is
(a)

3 3 (p / p ) 
  1 

4
K p0 

(b)

3 (p / p 0 ) 
  1 

4 K 0p 


(c)

3 (p / p 0 ) 
  1 

4 K C 

(d)

3 3 (p / p 0 ) 
  1 

4
K C 

0
1 / 2
Column - B
(A)
Kp = 79.1 at 4000C.
1 / 2
1 / 2
1 / 2
Matching-2
Column - A
The value of KC0 for the given reaction is
(a)
4.414
(b)
3.414
(c)
2.414
(d)
1.414
Comprehension-3
COCl2 gas dissociates according to the equation
COCl2
(d)
0
Column - A
0
5.
0.335
Matching-1
For a reaction
NH3(g)
(b)
MATRIX-MATCH TYPE
(a)
Comprehension-2
4.
The degree of dissociation is
Comprehension-1
(A)
Column - B
At constant temperature (p)
the decomposition reaction
is N2O4
2NO2. Kp
increases with the
increase of
pressure
CO + Cl2
When COCl2 is heated to 724 K at 101.325 kPa,
density of the gas mixture at equilibrium is
1.162 g dm–3.
Einstein Classes,
Unit No. 102, 103, Vardhman Ring Road Plaza, Vikas Puri Extn., Outer Ring Road
New Delhi – 110 018, Ph. : 9312629035, 8527112111
CCE – 10
(B)
For the reaction
3x(g) + y(g)
X3Y(g), the amount
of X3Y at equilibrium is
affected by
(q)
temperature
(C)
For the reaction
CO(g) + H2O(g)
CO2(g) + H2(g), at
a given temperature
by equilibrium amt.
of CO2 gas can be
increased by
(r)
catalyst
(D)
(a)
5.
For the reaction
(s)
N2(g) + O2(g)
2NO(g). The factor
will cause the equilibrium
constant to increase
adding inert
gas
MULTIPLE CORRECT CHOICE TYPE
1.
2.
3.
4.
For the reaction
PCl5(g)
PCl3(g) + Cl2(g)
the forward reaction at constant temperature is
favoured by
(a)
introducing an inert gas at constt. volume
(b)
introducing Cl2 gas at contt. volume
(c)
introducing an inert gas at contt.
pressure
(d)
increasing the volume of the container
For a reaction in a close vessel
SO2(g) + Cl2(g)
SO2Cl(l) + E
extra quantity of SO2 is introduced into the vessel,
the volume remaining the same which of the
following are true
(a)
the pressure in side the vessel will change
(b)
the temperature will not change
(c)
the temperature will increase
(d)
the temperature will decrease
When solid NaNO 3 is heated in a close vessel
oxygen is liberated and NaNO3 is left behind. At
eqm.
(a)
addition of NaNO3 favours reverse
reaction
(b)
addition of NaNO3 favours forward
reaction
(c)
increasing temperature favours forward
reaction
(d)
increasing pressure favours reverse
reaction
For the reaction :
A(g)
B(g) + C(g)
kp at 773 k = 1.8 × 10–4
kp at 873 k = 6.4 × 10–6
then
Einstein Classes,
6.
7.
8.
the formation of B and C from A is
exothermic
(b)
the formation of B and C from A is
endothermic
(c)
increase the temperature would shift the
equilibrium towards right
(d)
increase of pressure would shift the
equilibrium towards left
A flask of 800 ml capacity contains two gases A and
B at partial pressures of 0.6 atm and 0.8 atm
respectively. When 100 ml of N2 gas at pressure of
4 atm is admitted to this flask then
(a)
partial pressure of A and B would
increase
(b)
partial pressures of A and B would
decrease
(c)
partial pressures of A and B would not
change
(d)
partial pressure of N2 in the flask is
0.5 atm
For the reaction
N2O4(g)
2NO2(g)
Kp (in atm) = 1.7 × 103 at 500 k
Kp (in atm) = 1.78 × 104 at 600 k
which of the following statements are true
(a)
H = –ve value
(b)
Kp = Kc
(c)
the formation of NO2 in the mixture
increases on increasing the volume of the
reaction vessel
(d)
units of Kp are atm
The equilibrium for the reaction
SO2Cl2(g)
SO2(g) + Cl2(g)
is attained at 298k in a closed container and inert
gas helium is introduced. Which of the following
statements are true ?
(a)
conc. of SO2, Cl2 and SO2Cl2 change
(b)
more Cl2 will formed
(c)
conc. of SO2 is reduced
(d)
more SO2Cl2 is formed
Pure ammonia is placed in a vessel at a
temperature where its dissociation constant is
appreciable. At eqm.
(a)
kp does not change signifinally with
pressure
(b)
 does not change with pressure
(c)
conc. of NH3 does not change with
pressure
(d)
conc. of H2 < N2
Unit No. 102, 103, Vardhman Ring Road Plaza, Vikas Puri Extn., Outer Ring Road
New Delhi – 110 018, Ph. : 9312629035, 8527112111
CCE – 11
9.
10.
11.
12.
Which of the following statements about the
reaction quotient, Q are correct
(a)
the Q and K always have same
numerical value
(b)
Q may be > or < = K
(c)
Q (numerical value) varies as reaction
proceeds
(d)
at eqm. Q = unity
Which of the following factors will increase the
solubility of NH3 in water
NH3 + H2O
NH4OH
(a)
increase in pressure
(b)
addition of water
(c)
liquification of NH3
(d)
decrease in pressure
Volume of the flask in which following species are
transfereed is double of the earlier flask. In which
of the following case (s) eqm. contt. is affected
(a)
N2(g) + 3H2(g)
2NH3(g)
(b)
2NO(g)
N2(a) + O2(g)
(c)
PCl5(g)
PCl3(g) + Cl2(g)
(d)
N2(g) + O2(g)
2NO(g)
Which are correct relationship for equilibrium
constant K
E 0 cell nF
2.303 RT
(a)
log K c 
(b)
G0 = –RT In Kc
(c)
K
H 0 T2  T1
log 2 
K 1 2.303 R T1T2
(d)
K
1.
Assertion-Reason Type
Each question contains STATEMENT-1 (Assertion)
and STATEMENT-2 (Reason). Each question has
4 choices (A), (B), (C) and (D) out of which ONLY
ONE is correct.
(A)
Statement-1 is True, Statement-2 is True;
Statement-2 is a correct explanation
for Statement-1
(B)
Statement-1 is True, Statement-2 is True;
Statement-2 is NOT a correct
explanation for Statement-1
(C)
Statement-1 is True, Statement-2 is False
(D)
Statement-1 is False, Statement-2 is True
STATEMENT-1 : For the reaction
N2(g) + O2(g)
2NO(g)
Change of pressure has no effect in case of the
equilibrium.
STATEMENT-2 : The reaction
N2(g) + O2(g)
2NO(g)
is highly endothermic reaction.
2.
STATEMENT-1 : The value of equilibrium
constant k, increases with increase in
temperature in case of endothermic reactions.
STATEMENT-2 : The increase in temperature
shifts the equilibrium in back-ward direction in
case of exothermic reactions.
3.
STATEMENT-1 : In case of evaporation of
water, the vapour pressure of liquid becomes
constant at equilibrium.
STATEMENT-2 : At equilibrium the measurable
properties of the system becomes constant.
4.
 [productus]
 [Re ac tan ts]
STATEMENT-1 : Formation of ammonia by
Haber’s process is affected by change of
temperature.
STATEMENT-2 : The reaction is endothermic in
forward direction.
5.
STATEMENT-1 : In the equilibrium constant
expressions, we cannot use the terms of
concentration.
STATEMENT-2 : No, units are written with the
equilibrium constant.
(Answers) EXCERCISE BASED ON NEW PATTERN
COMPREHENSION TYPE
1.
a
2.
b
3.
7.
c
8.
c
MATRIX-MATCH TYPE
1.
[A-s; B-q; C-p; D-r]
2.
MUTIPLE CORRECT CHOICE TYPE
1.
c, d
2.
a, c
3.
7.
c, d
8.
a, b, c, d
12.
a, b, c
ASSERTION-REASON TYPE
1.
B
2.
B
3.
Einstein Classes,
c
4.
a
5.
d
6.
a
6.
11.
c, d
a, c
[A-p, q; B-p, q, s; C-q; D-q]
b, c, d
4.
9.
a, d
b, c
5.
10.
c, d
a, b
A
4.
C
5.
A
Unit No. 102, 103, Vardhman Ring Road Plaza, Vikas Puri Extn., Outer Ring Road
New Delhi – 110 018, Ph. : 9312629035, 8527112111
CCE – 12
INITIAL STEP EXERCISE
(SUBJECTIVE)
1.
Kp for the equilibrium, FeO(s) + CO(g)
Fe(s) + CO2(g) at 1000 0C is 0.4. If CO(g) at a
pressure of 1 atm and excess FeO(s) are placed in a
container at 10000C, what are the pressures of
CO(g) and CO2(g) when equilibrium is attained ?
2.
NO and Br2 at initial partial pressures of 98.4 and
41.3 torr, respectively, were allowed to react at 300
K. At equilibrium the total pressure was 110.5 torr.
Calculate the value of the equilibrium constant kP
and the standard free energy change at 300 K for
the reaction 2NO(g) + Br2(g)
3.
9.
What total pressure must be used to obtain a 10%
conversion of hydrogen to ammonia at 400 0C,
assuming an initially equimolar mixture of
nitrogen and hydrogen and ideal gas behaviour ?
The equilibrium constant for the formation of
NH3(g) with a standard state pressure of 1 bar is
1.60 × 10–4 at 4000C.
10.
Consider the vapour phase dissociation of an
oxoacid HXO3 according to the equation, 4HXO3(g)
4XO 2(g) + 2H 2O(g) + O 2(g). Derive the
H2S(g) + NH3(g)
If solid NH4HS is placed in an evacuated flask at a
certain temperature, it will dissociate until the
total gas pressure is 500 torr. (a) Calculate the value
of the equilibrium constant for the dissociation
reaction. (b) Additional NH3 is introduced into the
equilibrium mixture without change in
temperature until the partial pressure of ammonia
is 700 torr. What is the partial pressure of H2S
under these conditions ? What is the total pressure
in the flask ?
4.
If 1.588 g of nitrogen tetroxide gives a total
pressure of 1.0133 bar when partially dissociated
in a 500-cm3 glass vessel at 250C, what is the extent
of reaction ? What is the value of K ? What is the
extent of reaction at a total pressure of 0.5 bar ?
2NOBr(g)
Ammonium hydrogen sulfide dissociates as
follows :
NH4HS(s)
8.
expression : K p
11.
NOBr(g)
N2(g) + O2(g);
NO(g) + 1/2Br2(g)
5.
At
a
certain
KC
In an equilibrium A(g) + B(g)
C(g) + D(g); A
and B are mixed in a vessel at temperature T. The
initial concentration of A was twice the initial
concentration of B. After the equilibrium has
reached, concentration of C was thrice the
equilibrium concentration of B. Calculate KC.
13.
Calculate the equilibrium constant for the
following reaction at the indicated temperature.
for
SO 2 ( g )  NO 2 ( g )  SO 3( g )  NO ( g ) is 16. If we take

one mole of each of all the four gases in one litre
container, what would be the equilibrium
concentrations of NO and NO2 ?
6.
7.
(a)
NH 3 is heated at 15 atm from 27 0C to 347 0 C
assuming volume constant. The new pressure
becomes 50 atm at equilibrium of the reaction 2NH3
N2 + 3H2. Calculate % of moles of NH3
actually decomposes.
The density of an equilibrium mixture of N2O4 and
NO2 at 1 atm and 348 K is 1.84 g dm–3. Calculate
the equilibrium constant, K P of the reaction
N2O4(g)
2NO2(g).
Einstein Classes,
2NH3(g)
12.
NOBr(g);K2 = 1.4
temperature,
where P is the
(a) What is the value of the standard Gibbs energy
for following reaction at 4000C ? (b) What is the
value of the equilibrium constant and the standard
reaction Gibbs energy when reaction is divided by
two ? (c) What is the value of the equilibrium
constant and the standard reaction Gibbs energy
when reaction is reversed ?
N2(g) + 3H2(g)
K1 = 2.4 × 1030
4
total pressure and p O 2 is partial pressure of O2.
from the following information (at 298 K)
2NO (g)
7
O2
Determine K C for the reaction 1/2N 2 (g) +
1/2O2(g) + 1/2Br2(g)
 

P  7p 
1024 p O 2
3O2(g) = 2O3(g) at 250C
[G0f (O3, g) = 163.2]
(b)
14.
CO(g) + 2H2(g) = CH3OH(g) at 500 K
[G0f(CH3OH, g) = –134.27,
G0f (CO, g) = –155.44
A mixture of SO3, SO2 and O2 gases is maintained
at equilibrium in 10 litre flask at a temperature at
which KC for the reaction, 2SO2(g) + O2(g)
2SO3(g) is 100. At equilibrium.
(a)
If number of moles of SO3 and SO2 in
flask are same, how many moles of O2 are
present.
Unit No. 102, 103, Vardhman Ring Road Plaza, Vikas Puri Extn., Outer Ring Road
New Delhi – 110 018, Ph. : 9312629035, 8527112111
CCE – 13
(b)
15.
If number of moles of SO3 in flask are
twice the number of moles of SO2, how
many moles of O2 are present ?
CO2(g) + H2(g)
present in a vessel of one litre capacity at 8150C
was found by analysis to contain 0.4 mole of CO,
0.3 mole of H2O, 0.2 mole of CO2 and 0.6 mole of
H2. If it is desired to increase the concentration of
CO to 0.6 mole by adding CO2 to the vessel, how
many moles must be added into equilibrium
mixture at constant temperature in order to get this
change ?
18.
32 g of H2 and 112 g of N2 are sealed with a suitable
catalyst in a one litre vessel. The vessel is heated at
a constant temperature until equilibrium is
established, when it is found that the pressure in
the vessel has falled to 9/10th of its original value.
Calculate Kc for the reaction, N2(g) + 3H2(g)
2NH3(g).
19.
Show that KP for the reaction
2H2S(g)
For the gaseous reaction
C2H2 + D2O
C2D2 + H2O; H is 530 cal.
0
At 25 C Kp = 0.82. Calculate how much C2D2 will
be formed if 1 mole of C2H2 and 2 moles of D2O are
put together at a total pressure of 1 atm at 1000C.
An equilibrium mixture of
CO(g) + H2O(g)
16.
17.
For the reaction
SnO2(s) + 2H2(g)
2H2(g) + S2(g)
2H2O(g) + Sn(l)
At 900 K, where the equilibrium stream-hydrogen
mixture was 45% H2 by volume and at 1100 K,
where the equilibrium stream-hydrogen mixture
was 24% H 2 by volume. Calculate activation
energy for the backward reaction, if the activation
energy for the forward reaction is 98.09 kJ/mol.
is given by the expression
 3P
Kp 
(2  )(1  ) 2
where  is the degree of dissociation and P is the
total equilibrium pressure. Calculate KC of the
reaction, if  at 298 K and 1 atm pressure is 0.055.
FINAL STEP EXERCISE
(SUBJECTIVE)
1.
One mole of N2 and 3 moles of PCl5 are placed in a
100 litre vessel heated to 2270C. The equilibrium
pressure is 2.05 atm. Assuming ideal behaviour,
calculate degree of dissociation of PCl5 and Kp of
5.
An equilibrium mixture at 300 K contains N2O4 and
NO2 at 0.28 and 1.1 atmosphere respectively. If the
volume of container is doubled, calculated the new
equilibrium pressure of two gases.
the reaction : PCl5
6.
Ammonium
PCl3 + Cl2.
wit PCO = 10 bar, PH 2 = 1 bar, and PCH 3OH  0.1
bar is passed over a catalyst. Can more methanol
be formed ?
(b)
Can the following conversion occur at 500 K ?
CO(g, 1 bar) + 2H2 (g, 10 bar)
(g, 0.1 bar)
3.
4.
The KP for the reaction N2O4(g)
2NO2(g) is
640 mm Hg at 775 K. Calculate the percentage
dissociation of N2O4 at equilibrium pressure of 160
mm Hg. At what pressure, the dissociation will be
50 % ?
Einstein Classes,
7.
CH3OH
The degree of dissociation of HI at a particular
temperature is 0.8. Calculate the volume of 2 M
Na2S2O3 solution required to neutralise the iodine
present in a equilibrium mixture of a reaction when
2 mole each of H2 and I2 are heated in a closed
vessel of 2 litre capacity.
dissociates
as
NH2COONH4(s)
2NH 3(g) + CO 2(g). In a
closed vessel containing ammonium carbanate in
equilibrium, ammonia is added such that partial
pressure of NH3 at the new equilibrium equals to
the original total pressure. Calculate the ratio of
total pressure now to the original pressure.
2.(a). A mixture of CO(g), H2(g), and CH3OH(g) at 500 K
Given : rG0 = 21.2 kJ mol–1.
carbamate
At 2500C and 1 atm pressure, PCl5 was found to
have decomposed to the extent of 80% according
to the reaction, PCl5(g)
PCl3(g) + Cl2(g). At
what pressure and at the same temperature, the
ratio of PCl5 : PCl3 in the equilibrium mixture would
be
(a)
8.
1:5
(b)
5:1
–3
8 × 10 moles of an ideal gas A is filled in a
container of volume 500 ml at 27 0 C. The
temperature is then raised to 6000C, when A comes
to equilibrium according to the equation A(g)
B(g) + C(g) with a dissociation equilibrium
constant of KP = 2.8 atm. Calculate the partial
pressures of A and B at 600 0C and the total
pressure at equilibrium.
Unit No. 102, 103, Vardhman Ring Road Plaza, Vikas Puri Extn., Outer Ring Road
New Delhi – 110 018, Ph. : 9312629035, 8527112111
CCE – 14
9.
500 ml of 0.15 M AgNO3 are added to 500 ml of
1.09 M ferrous sulphate solution and the reaction
is allowed to reach equilibrium at 250 C. 25 ml of
the equilibrium mixture requires 30 ml of 0.0832
M KMnO 4 for oxidation in acidic medium.
Calculate KC for the reaction.
Ag+(aq) + Fe2+(aq)
10.
11.
Ag(s) + Fe3+(aq)
Pure PCl 5 is introduced into an evacuated
chamber and comes to equilibrium at 2500C and
2.00 atm. The equilibrium gas contains 40.7%
chlorine by volume. Now, if the gas mixture is
expanded to 0.2 atm at 2500C. Calculate.
(a)
Percentage of PCl5 that would be
dissociated at equilibrium
(b)
Percent by volume of Cl2 in the
equilibrium gas mixture.
(c)
the partial pressure of Cl2 in the
equilibrium mixture.
The following gaseous equilibrium was obtained by
heating 0.460 moles of A in a 5 litre vessel. The
equilibrium pressure at 300 K was 3.0 atm. The
equilibrium pressure changed to 3.6 atm when
temperature was raised to 320 K. Calculate the
percentage change in degree of dissociation of A at
350 K with respect to that of at 300 K.
A(g)
In an initially equimolar mixture of nitrogen and
hydrogen is placed in contact with an ammonia
catalyst at 400 0C and 51.2 bar, there is a 10%
conversion to ammonia at equilibrium. What
pressure is required to obtain a 15% conversion ?
13.
A sample of air consisting of N2 and O2 was heated
to 2500 K until the equilibrium
N2(g) + O2(g)
The progress of the reaction A
nB, with
2CO(g) in atm.
16.
What is the minimum weight of solid NH4HS which
must be added to a 5 litre container so that the
equilibrium is established between solid NH4HS and
its decomposition products (NH3 & H2S) at 200C.
KP of the decomposition of NH4HS to NH3 & H2S is
5.48 × 10–2 atm2.
17.
A 100 litre flask vessel contains 10 moles each of
nitrogen and hydrogen at 5040C. The two gases were
made to react and at equilibrium, the partial
pressure of hydrogen was 1 atm. Find Kc for the
equilibrium reaction. At this point, five litre water
was injected and the gas mixture was cooled
suddenly to 298 K. Find out the final gas pressure
immediately after cooling ?
18.
An equilibrium mixture of 2 moles each of PCl5,
PCl3 and Cl2 is maintained in a volume ‘V’ litres at
temperature ‘T’ and a total pressure of 3
atmosphere. Cl2 is now added maintained the same
pressure and temperature till the volume is doubled.
How many moles of Cl2 were added.
19.
At 1393 K
2 NO (g)
was established with an equilibrium constant
Kc = 2.1 × 10–3. At equilibrium, the mole % of NO
was 1.8. Estimate the initial composition of air in
mole fraction of N2 and O2.
When a mixture of SrCO 3 (s), SrO(s) and
C(graphite) is heated, a gas phase containing CO2
and CO is produced. At 850 0C in a previously
evacuated vessel, a pressure of 171 mm is produced.
At the same temperature, the measured
dissociation pressure of SrCO3 is 2.47 mm.Calculate
KP for the reaction
C(graphite) + CO2(g)
B(g) + C(g)
12.
14.
15.
Fe2O3(s) + 3CO(g) = 2Fe(s) + 3CO2(g)
K = 0.0467
2CO2(g) = 2CO(g) + O2(g)
K = 1.4 × 10–12
time is
presented in the figure
Determine :
(i)
the value of n,
(ii)
the equilibrium constant, K, and
(iii)
the initial rate of convertion of A.
Einstein Classes,
What is the equilibrium pressure of O 2(g) in a
vessel containing Fe2O3(s) and Fe(s) at equilibrium
at 1393 K ?
Unit No. 102, 103, Vardhman Ring Road Plaza, Vikas Puri Extn., Outer Ring Road
New Delhi – 110 018, Ph. : 9312629035, 8527112111
CCE – 15
ANSWERS SUBJECTIVE (INITIAL STEP EXERCISE)
7.
5.026 atm
8.
9.
P = 51.2 bar
11.
(a)
48.91 kJ/mol (b)
(c)
K = 6250, G0 = –48.91 kJ/mol
.01842, 0.143, 0.258]
24.46 kJ/mol, K = .01265
12.
1.80
13.
(a)
K = 6.62 × 10–58
(b)
K = 6.14 × 10–3
14.
(a)
0.1,
15.
0.75
16.
KC = 3.71 × 10–6
17.
0.66
18.
6.07 × 10–4
(b)
0.4
ANSWERS SUBJECTIVE (FINAL STEP EXERCISE)
2.
(a) Thus, the reaction as written is not spontaneous. (b) Under these conditions the
reaction is thermodynamically spontaneous.
3.
1.6 lit.
4.
70.7 %, 480 mm of Hg
5.
PN 2O 4  0.096 atm ; PNO 2  0.64 atm
6.
31/27
7.
(a)
(b)
61.95 atm
8.
PA = 0.273 atm, PB = 0.873 atm, Ptotal = 2.019 atm
9.
3.14
11.
50%
12.
P = 107.2 bar
13.
% N2 = 78.4 %, %O2 = 21.6
18.
6.6 mol
19.
Po 2  1.82 1013 bar
0.778 atm
Einstein Classes,
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New Delhi – 110 018, Ph. : 9312629035, 8527112111