Solved Example: Chemical Equilibrium | Chemistry for JEE Main & Advanced PDF Download

 Page 1


           JEE Solved Example on Chemical Equilibrium 
JEE Mains 
Q1:  Which is false? 
(A) The greater the concentration of the substance involved in a reaction, the lower the speed of 
the reaction 
(B) The dissociation of weak electrolyte is a reversible reaction 
(C) The presence of free ions facilities chemical changes 
(D) All of the above 
Ans:  (A) As we increases the concentration of substance, then speed of the reaction increases. 
Q2:  Chemical equations convey quantitative information on the: 
(A) Type of atoms/molecules taking part in the reaction 
(B) Relative number of moles of reactants and products involved in the reaction 
(C) Number of atoms/molecules of the reactants and products involved in the reaction 
(D) Quantity of reactant consumed and quantity of product formed. 
Ans: (B) Chemical reaction quantitatively depend on the reactant and product molecule. 
Q3:  In the thermal decomposition of potassium chlorate given as: 
?? ???????? ?? ? ???????? + ?? ?? ?? , law of mass action: 
(A) Can be applied 
(B) Cannot be applied 
(C) Can be applied at low temperature 
(D) Can be applied at high temperature and pressure 
Ans: (B) In the thermal decomposition of potassium chlorate given as: 
2KClO
3
? 2KCl+ 3O
2
, law of mass action cannot be applied. 
Q4:  In which of the following, the reaction proceeds towards completion? 
(A) ?? = ?? 
(B) ?? = ???? 
(C) ?? = ????
?? 
(D) ?? = ????
?? 
Ans:  (D) Those reaction which have more value of K proceeds towards completion. 
Q6 Pure ammonia is placed in a vessel at temperature where its dissociation constant ( ?? ) is 
appreciable. At equilibrium: 
(A) ?? ?? does not change significantly with pressure 
(B) ?? does not change with pressure 
(C) Concentration of ????
?? does not change with pressure 
(D) Concentration of ?? ?? is less than that of ?? ?? 
Ans:(A) ?? ?? is a constant and does not change with pressure. 
 
Page 2


           JEE Solved Example on Chemical Equilibrium 
JEE Mains 
Q1:  Which is false? 
(A) The greater the concentration of the substance involved in a reaction, the lower the speed of 
the reaction 
(B) The dissociation of weak electrolyte is a reversible reaction 
(C) The presence of free ions facilities chemical changes 
(D) All of the above 
Ans:  (A) As we increases the concentration of substance, then speed of the reaction increases. 
Q2:  Chemical equations convey quantitative information on the: 
(A) Type of atoms/molecules taking part in the reaction 
(B) Relative number of moles of reactants and products involved in the reaction 
(C) Number of atoms/molecules of the reactants and products involved in the reaction 
(D) Quantity of reactant consumed and quantity of product formed. 
Ans: (B) Chemical reaction quantitatively depend on the reactant and product molecule. 
Q3:  In the thermal decomposition of potassium chlorate given as: 
?? ???????? ?? ? ???????? + ?? ?? ?? , law of mass action: 
(A) Can be applied 
(B) Cannot be applied 
(C) Can be applied at low temperature 
(D) Can be applied at high temperature and pressure 
Ans: (B) In the thermal decomposition of potassium chlorate given as: 
2KClO
3
? 2KCl+ 3O
2
, law of mass action cannot be applied. 
Q4:  In which of the following, the reaction proceeds towards completion? 
(A) ?? = ?? 
(B) ?? = ???? 
(C) ?? = ????
?? 
(D) ?? = ????
?? 
Ans:  (D) Those reaction which have more value of K proceeds towards completion. 
Q6 Pure ammonia is placed in a vessel at temperature where its dissociation constant ( ?? ) is 
appreciable. At equilibrium: 
(A) ?? ?? does not change significantly with pressure 
(B) ?? does not change with pressure 
(C) Concentration of ????
?? does not change with pressure 
(D) Concentration of ?? ?? is less than that of ?? ?? 
Ans:(A) ?? ?? is a constant and does not change with pressure. 
 
Q7: 2 moles of ?????? ?? were heated vessel of ?? ?? capacity. At equilibrium ???? % of ?????? ?? is dissociated 
into ?????? ?? and ????
?? . The value of equilibrium constant is: 
(A) 0.266 
(B) 0.366 
(C) 2.66 
(D) 3.66 
Ans: (A) 
PCl
5
PCl
3
+ Cl
2
0 0 0 initially 
2 × 60
100
2 × 40
100
2 × 40
100
 at equilibrium 
 
Volume of container = 2 L. 
K
c
=
2 × 40
100 × 2
×
2 × 40
100 × 2
2 × 60
100 × 2
= 0.266 
 
Q8:  The decomposition of ?? ?? ?? ?? and ????
?? is carried out at ?????? ?? in chloroform. When equilibrium 
has been established, 0.2 mole of ?? ?? ?? ?? and ?? × ????
-?? mole of ????
?? are present in ?? ?? solution. 
The equilibrium constant for reaction, ?? ?? ?? ?? ? ?? ????
?? is: 
(A) ?? × ????
-?? 
(B) ?? × ????
-?? 
(C) ?? × ????
-?? 
(D) ?? × ????
-?? 
Ans: (D) 
K
c
=
[NO
2
]
2
[ N
2
O
4
]
=
[2 ×
10
-3
2
]
[
0.2
2
]
 =
10
-6
10
-1
= 10
-5
 
 
Q?? :  ?? + ?? ? ?? + ?? . If finally the concentration of ?? and ?? are both equal but at equilibrium, 
concentration of ?? will be twice of that of ?? then what will be the equilibrium constant of 
reaction? 
(A) 2 
(B) 4 
(C) 
?? ?? 
(D) 
?? ?? 
Ans:  (B) 
Page 3


           JEE Solved Example on Chemical Equilibrium 
JEE Mains 
Q1:  Which is false? 
(A) The greater the concentration of the substance involved in a reaction, the lower the speed of 
the reaction 
(B) The dissociation of weak electrolyte is a reversible reaction 
(C) The presence of free ions facilities chemical changes 
(D) All of the above 
Ans:  (A) As we increases the concentration of substance, then speed of the reaction increases. 
Q2:  Chemical equations convey quantitative information on the: 
(A) Type of atoms/molecules taking part in the reaction 
(B) Relative number of moles of reactants and products involved in the reaction 
(C) Number of atoms/molecules of the reactants and products involved in the reaction 
(D) Quantity of reactant consumed and quantity of product formed. 
Ans: (B) Chemical reaction quantitatively depend on the reactant and product molecule. 
Q3:  In the thermal decomposition of potassium chlorate given as: 
?? ???????? ?? ? ???????? + ?? ?? ?? , law of mass action: 
(A) Can be applied 
(B) Cannot be applied 
(C) Can be applied at low temperature 
(D) Can be applied at high temperature and pressure 
Ans: (B) In the thermal decomposition of potassium chlorate given as: 
2KClO
3
? 2KCl+ 3O
2
, law of mass action cannot be applied. 
Q4:  In which of the following, the reaction proceeds towards completion? 
(A) ?? = ?? 
(B) ?? = ???? 
(C) ?? = ????
?? 
(D) ?? = ????
?? 
Ans:  (D) Those reaction which have more value of K proceeds towards completion. 
Q6 Pure ammonia is placed in a vessel at temperature where its dissociation constant ( ?? ) is 
appreciable. At equilibrium: 
(A) ?? ?? does not change significantly with pressure 
(B) ?? does not change with pressure 
(C) Concentration of ????
?? does not change with pressure 
(D) Concentration of ?? ?? is less than that of ?? ?? 
Ans:(A) ?? ?? is a constant and does not change with pressure. 
 
Q7: 2 moles of ?????? ?? were heated vessel of ?? ?? capacity. At equilibrium ???? % of ?????? ?? is dissociated 
into ?????? ?? and ????
?? . The value of equilibrium constant is: 
(A) 0.266 
(B) 0.366 
(C) 2.66 
(D) 3.66 
Ans: (A) 
PCl
5
PCl
3
+ Cl
2
0 0 0 initially 
2 × 60
100
2 × 40
100
2 × 40
100
 at equilibrium 
 
Volume of container = 2 L. 
K
c
=
2 × 40
100 × 2
×
2 × 40
100 × 2
2 × 60
100 × 2
= 0.266 
 
Q8:  The decomposition of ?? ?? ?? ?? and ????
?? is carried out at ?????? ?? in chloroform. When equilibrium 
has been established, 0.2 mole of ?? ?? ?? ?? and ?? × ????
-?? mole of ????
?? are present in ?? ?? solution. 
The equilibrium constant for reaction, ?? ?? ?? ?? ? ?? ????
?? is: 
(A) ?? × ????
-?? 
(B) ?? × ????
-?? 
(C) ?? × ????
-?? 
(D) ?? × ????
-?? 
Ans: (D) 
K
c
=
[NO
2
]
2
[ N
2
O
4
]
=
[2 ×
10
-3
2
]
[
0.2
2
]
 =
10
-6
10
-1
= 10
-5
 
 
Q?? :  ?? + ?? ? ?? + ?? . If finally the concentration of ?? and ?? are both equal but at equilibrium, 
concentration of ?? will be twice of that of ?? then what will be the equilibrium constant of 
reaction? 
(A) 2 
(B) 4 
(C) 
?? ?? 
(D) 
?? ?? 
Ans:  (B) 
?? + ?? ? ?? + ?? ?? ?? 0 0
2 × 2 = 4
 
 
Q10: In the reaction, ?? ?? ?? ?? ? ?? ????
?? , ?? is that part of ?? ?? ?? ?? which dissociates, then the number of 
moles at equilibrium will be: 
(A) 1 
(B) 3 
(C) (?? + ?? ) 
(D) (?? - ?? )
?? 
Ans:  (C) 
N
2
O
4
? 2NO
2
1 2 initially 
 (1 - ?? ) 2??  at equilibrium 
 Total moles at equilibrium = (1 - ?? ) + 2?? = 1 + ?? 
 
Q11:  In a chemical equilibrium, the rate constant of the backward reaction is ?? . ?? × ????
-?? and the 
equilibrium constant is 1.5 . So, the rate constant of the forward reaction is: 
(A) ?? . ?????? × ????
-?? 
(B) ?? . ?????? × ????
-?? 
(C) ?? . ?????? × ????
-?? 
(D) ?? . ?????? × ????
-?? 
Ans: (A) ?? ?? =
?? ?? ?? ?? 
? ?? ?? = ?? ?? × ?? ?? = 1.5 × 7.5 × 10
-4
= 1.125× 10
-3
 
 
 
Q???? :    ???? ?? of ?? ?? and ?? ?? of ?? ?? were kept at ?? in ?? ?? vessel, the equilibrium mixture contained 
???? . ???? ?? of ????
?? . The approximate value of ?? ?? for the above reaction can be (in ?????? -?? ?? ?? ): 
(A) 25 
(B) 50 
(C) 75 
(D) 100 
Ans: (C) 
N
2
 +3H
2
 ? NH
3
 
Page 4


           JEE Solved Example on Chemical Equilibrium 
JEE Mains 
Q1:  Which is false? 
(A) The greater the concentration of the substance involved in a reaction, the lower the speed of 
the reaction 
(B) The dissociation of weak electrolyte is a reversible reaction 
(C) The presence of free ions facilities chemical changes 
(D) All of the above 
Ans:  (A) As we increases the concentration of substance, then speed of the reaction increases. 
Q2:  Chemical equations convey quantitative information on the: 
(A) Type of atoms/molecules taking part in the reaction 
(B) Relative number of moles of reactants and products involved in the reaction 
(C) Number of atoms/molecules of the reactants and products involved in the reaction 
(D) Quantity of reactant consumed and quantity of product formed. 
Ans: (B) Chemical reaction quantitatively depend on the reactant and product molecule. 
Q3:  In the thermal decomposition of potassium chlorate given as: 
?? ???????? ?? ? ???????? + ?? ?? ?? , law of mass action: 
(A) Can be applied 
(B) Cannot be applied 
(C) Can be applied at low temperature 
(D) Can be applied at high temperature and pressure 
Ans: (B) In the thermal decomposition of potassium chlorate given as: 
2KClO
3
? 2KCl+ 3O
2
, law of mass action cannot be applied. 
Q4:  In which of the following, the reaction proceeds towards completion? 
(A) ?? = ?? 
(B) ?? = ???? 
(C) ?? = ????
?? 
(D) ?? = ????
?? 
Ans:  (D) Those reaction which have more value of K proceeds towards completion. 
Q6 Pure ammonia is placed in a vessel at temperature where its dissociation constant ( ?? ) is 
appreciable. At equilibrium: 
(A) ?? ?? does not change significantly with pressure 
(B) ?? does not change with pressure 
(C) Concentration of ????
?? does not change with pressure 
(D) Concentration of ?? ?? is less than that of ?? ?? 
Ans:(A) ?? ?? is a constant and does not change with pressure. 
 
Q7: 2 moles of ?????? ?? were heated vessel of ?? ?? capacity. At equilibrium ???? % of ?????? ?? is dissociated 
into ?????? ?? and ????
?? . The value of equilibrium constant is: 
(A) 0.266 
(B) 0.366 
(C) 2.66 
(D) 3.66 
Ans: (A) 
PCl
5
PCl
3
+ Cl
2
0 0 0 initially 
2 × 60
100
2 × 40
100
2 × 40
100
 at equilibrium 
 
Volume of container = 2 L. 
K
c
=
2 × 40
100 × 2
×
2 × 40
100 × 2
2 × 60
100 × 2
= 0.266 
 
Q8:  The decomposition of ?? ?? ?? ?? and ????
?? is carried out at ?????? ?? in chloroform. When equilibrium 
has been established, 0.2 mole of ?? ?? ?? ?? and ?? × ????
-?? mole of ????
?? are present in ?? ?? solution. 
The equilibrium constant for reaction, ?? ?? ?? ?? ? ?? ????
?? is: 
(A) ?? × ????
-?? 
(B) ?? × ????
-?? 
(C) ?? × ????
-?? 
(D) ?? × ????
-?? 
Ans: (D) 
K
c
=
[NO
2
]
2
[ N
2
O
4
]
=
[2 ×
10
-3
2
]
[
0.2
2
]
 =
10
-6
10
-1
= 10
-5
 
 
Q?? :  ?? + ?? ? ?? + ?? . If finally the concentration of ?? and ?? are both equal but at equilibrium, 
concentration of ?? will be twice of that of ?? then what will be the equilibrium constant of 
reaction? 
(A) 2 
(B) 4 
(C) 
?? ?? 
(D) 
?? ?? 
Ans:  (B) 
?? + ?? ? ?? + ?? ?? ?? 0 0
2 × 2 = 4
 
 
Q10: In the reaction, ?? ?? ?? ?? ? ?? ????
?? , ?? is that part of ?? ?? ?? ?? which dissociates, then the number of 
moles at equilibrium will be: 
(A) 1 
(B) 3 
(C) (?? + ?? ) 
(D) (?? - ?? )
?? 
Ans:  (C) 
N
2
O
4
? 2NO
2
1 2 initially 
 (1 - ?? ) 2??  at equilibrium 
 Total moles at equilibrium = (1 - ?? ) + 2?? = 1 + ?? 
 
Q11:  In a chemical equilibrium, the rate constant of the backward reaction is ?? . ?? × ????
-?? and the 
equilibrium constant is 1.5 . So, the rate constant of the forward reaction is: 
(A) ?? . ?????? × ????
-?? 
(B) ?? . ?????? × ????
-?? 
(C) ?? . ?????? × ????
-?? 
(D) ?? . ?????? × ????
-?? 
Ans: (A) ?? ?? =
?? ?? ?? ?? 
? ?? ?? = ?? ?? × ?? ?? = 1.5 × 7.5 × 10
-4
= 1.125× 10
-3
 
 
 
Q???? :    ???? ?? of ?? ?? and ?? ?? of ?? ?? were kept at ?? in ?? ?? vessel, the equilibrium mixture contained 
???? . ???? ?? of ????
?? . The approximate value of ?? ?? for the above reaction can be (in ?????? -?? ?? ?? ): 
(A) 25 
(B) 50 
(C) 75 
(D) 100 
Ans: (C) 
N
2
 +3H
2
 ? NH
3
 
1 3   
1 - 0.81 3 - 2.43 0 initially 
(= 0.19) (= 0.57) 1.62 at equilibrium 
 
Number of moles of N
2
=
28
28
= 1 mol 
Number of moles of H
2
=
6
2
= 3 mol 
Number of moles of NH
3
=
27.54
17
= 1.62 mol 
? ?? ?? =
[NH
3
]
2
[ N
2
][H
2
]
3
=
[1.62]
2
[0.19][0.57]
3
= 75 
 
Q13:  A mixture of 0.3 mole of ?? ?? and 0.3 mole of ?? ?? is allowed to react in a ???? ?? evacuated flask 
at ??????
°
?? . The reaction is ?? ?? + ?? ?? ? ?????? , the ?? is found to be 64. The amount of unreacted at 
equilibrium is: 
(A) 0.03 mole 
(B) 0.06 mole 
(C) 0.09 mole 
(D) 3.6 moles 
Ans: (B) 
K
c
=
[HI ]
2
[H
2
][I
2
]
 ? 64 =
x
2
0.03 × 0.03
 ? ?? 2
= 64 × 9 × 10
-4
 
Or, ?? = 8 × 3 × 10
-2
 
?? is the amount of HI at equilibrium amount of I
2
 at equilibrium will be: 
0.30 - 0.24 = 0.06 
 
Q14:  The equilibrium concentration of ?? , ?? and ????
?? are 4,2 and 2 moles respectively for the 
equilibrium, ???? + ?? ? ???? . The value of ?? ?? is: 
(A) 0.625 
(B) 0.0625 
(C) 0.00625 
(D) 6.25 
Ans: (B) ?? ?? =
[YX
2
]
[X]
2
[Y]
=
2
4×4×2
=
1
16
= 0.0625 
Page 5


           JEE Solved Example on Chemical Equilibrium 
JEE Mains 
Q1:  Which is false? 
(A) The greater the concentration of the substance involved in a reaction, the lower the speed of 
the reaction 
(B) The dissociation of weak electrolyte is a reversible reaction 
(C) The presence of free ions facilities chemical changes 
(D) All of the above 
Ans:  (A) As we increases the concentration of substance, then speed of the reaction increases. 
Q2:  Chemical equations convey quantitative information on the: 
(A) Type of atoms/molecules taking part in the reaction 
(B) Relative number of moles of reactants and products involved in the reaction 
(C) Number of atoms/molecules of the reactants and products involved in the reaction 
(D) Quantity of reactant consumed and quantity of product formed. 
Ans: (B) Chemical reaction quantitatively depend on the reactant and product molecule. 
Q3:  In the thermal decomposition of potassium chlorate given as: 
?? ???????? ?? ? ???????? + ?? ?? ?? , law of mass action: 
(A) Can be applied 
(B) Cannot be applied 
(C) Can be applied at low temperature 
(D) Can be applied at high temperature and pressure 
Ans: (B) In the thermal decomposition of potassium chlorate given as: 
2KClO
3
? 2KCl+ 3O
2
, law of mass action cannot be applied. 
Q4:  In which of the following, the reaction proceeds towards completion? 
(A) ?? = ?? 
(B) ?? = ???? 
(C) ?? = ????
?? 
(D) ?? = ????
?? 
Ans:  (D) Those reaction which have more value of K proceeds towards completion. 
Q6 Pure ammonia is placed in a vessel at temperature where its dissociation constant ( ?? ) is 
appreciable. At equilibrium: 
(A) ?? ?? does not change significantly with pressure 
(B) ?? does not change with pressure 
(C) Concentration of ????
?? does not change with pressure 
(D) Concentration of ?? ?? is less than that of ?? ?? 
Ans:(A) ?? ?? is a constant and does not change with pressure. 
 
Q7: 2 moles of ?????? ?? were heated vessel of ?? ?? capacity. At equilibrium ???? % of ?????? ?? is dissociated 
into ?????? ?? and ????
?? . The value of equilibrium constant is: 
(A) 0.266 
(B) 0.366 
(C) 2.66 
(D) 3.66 
Ans: (A) 
PCl
5
PCl
3
+ Cl
2
0 0 0 initially 
2 × 60
100
2 × 40
100
2 × 40
100
 at equilibrium 
 
Volume of container = 2 L. 
K
c
=
2 × 40
100 × 2
×
2 × 40
100 × 2
2 × 60
100 × 2
= 0.266 
 
Q8:  The decomposition of ?? ?? ?? ?? and ????
?? is carried out at ?????? ?? in chloroform. When equilibrium 
has been established, 0.2 mole of ?? ?? ?? ?? and ?? × ????
-?? mole of ????
?? are present in ?? ?? solution. 
The equilibrium constant for reaction, ?? ?? ?? ?? ? ?? ????
?? is: 
(A) ?? × ????
-?? 
(B) ?? × ????
-?? 
(C) ?? × ????
-?? 
(D) ?? × ????
-?? 
Ans: (D) 
K
c
=
[NO
2
]
2
[ N
2
O
4
]
=
[2 ×
10
-3
2
]
[
0.2
2
]
 =
10
-6
10
-1
= 10
-5
 
 
Q?? :  ?? + ?? ? ?? + ?? . If finally the concentration of ?? and ?? are both equal but at equilibrium, 
concentration of ?? will be twice of that of ?? then what will be the equilibrium constant of 
reaction? 
(A) 2 
(B) 4 
(C) 
?? ?? 
(D) 
?? ?? 
Ans:  (B) 
?? + ?? ? ?? + ?? ?? ?? 0 0
2 × 2 = 4
 
 
Q10: In the reaction, ?? ?? ?? ?? ? ?? ????
?? , ?? is that part of ?? ?? ?? ?? which dissociates, then the number of 
moles at equilibrium will be: 
(A) 1 
(B) 3 
(C) (?? + ?? ) 
(D) (?? - ?? )
?? 
Ans:  (C) 
N
2
O
4
? 2NO
2
1 2 initially 
 (1 - ?? ) 2??  at equilibrium 
 Total moles at equilibrium = (1 - ?? ) + 2?? = 1 + ?? 
 
Q11:  In a chemical equilibrium, the rate constant of the backward reaction is ?? . ?? × ????
-?? and the 
equilibrium constant is 1.5 . So, the rate constant of the forward reaction is: 
(A) ?? . ?????? × ????
-?? 
(B) ?? . ?????? × ????
-?? 
(C) ?? . ?????? × ????
-?? 
(D) ?? . ?????? × ????
-?? 
Ans: (A) ?? ?? =
?? ?? ?? ?? 
? ?? ?? = ?? ?? × ?? ?? = 1.5 × 7.5 × 10
-4
= 1.125× 10
-3
 
 
 
Q???? :    ???? ?? of ?? ?? and ?? ?? of ?? ?? were kept at ?? in ?? ?? vessel, the equilibrium mixture contained 
???? . ???? ?? of ????
?? . The approximate value of ?? ?? for the above reaction can be (in ?????? -?? ?? ?? ): 
(A) 25 
(B) 50 
(C) 75 
(D) 100 
Ans: (C) 
N
2
 +3H
2
 ? NH
3
 
1 3   
1 - 0.81 3 - 2.43 0 initially 
(= 0.19) (= 0.57) 1.62 at equilibrium 
 
Number of moles of N
2
=
28
28
= 1 mol 
Number of moles of H
2
=
6
2
= 3 mol 
Number of moles of NH
3
=
27.54
17
= 1.62 mol 
? ?? ?? =
[NH
3
]
2
[ N
2
][H
2
]
3
=
[1.62]
2
[0.19][0.57]
3
= 75 
 
Q13:  A mixture of 0.3 mole of ?? ?? and 0.3 mole of ?? ?? is allowed to react in a ???? ?? evacuated flask 
at ??????
°
?? . The reaction is ?? ?? + ?? ?? ? ?????? , the ?? is found to be 64. The amount of unreacted at 
equilibrium is: 
(A) 0.03 mole 
(B) 0.06 mole 
(C) 0.09 mole 
(D) 3.6 moles 
Ans: (B) 
K
c
=
[HI ]
2
[H
2
][I
2
]
 ? 64 =
x
2
0.03 × 0.03
 ? ?? 2
= 64 × 9 × 10
-4
 
Or, ?? = 8 × 3 × 10
-2
 
?? is the amount of HI at equilibrium amount of I
2
 at equilibrium will be: 
0.30 - 0.24 = 0.06 
 
Q14:  The equilibrium concentration of ?? , ?? and ????
?? are 4,2 and 2 moles respectively for the 
equilibrium, ???? + ?? ? ???? . The value of ?? ?? is: 
(A) 0.625 
(B) 0.0625 
(C) 0.00625 
(D) 6.25 
Ans: (B) ?? ?? =
[YX
2
]
[X]
2
[Y]
=
2
4×4×2
=
1
16
= 0.0625 
 
Q15:  An amount of solid ????
?? ???? is placed in a flask already containing ammonia gas at a certain 
temperature and ?? . ???? ?????? pressure. Ammonia hydrogen sulphide decomposes to yield ????
?? and 
?? ?? ?? gases in the flask. When the decomposition reaction reaches equilibrium, the total pressure 
in the flask rises to 0.84 atm. The equilibrium constant for decomposition at this temperature is: 
(A) 0.11 
(B) 0.22 
(C) 0.33 
(D) 0.44 
Ans: (A) 
NH
4
HS (s) ? NH
3
( g) + H
2
 S( g)
 a  0.5 atm 0  initially 
 (?? - ?? ) 0.5 + ?? ??  at equilibrium 
 Total pressure = 0.5 + 2x = 0.84
 i.e., ?? = 0.17
 K
p
= P
NH
3
· P
H
2
 S
= (0.67) × (0.17) = 0.1139
 
 
 
Q16 A reaction is, ?? + ?? ? ?? + ?? , Initially we start with equal concentration of ?? , and ?? . At 
equilibrium we find the moles of ?? is two times of ?? . What is the equilibrium constant of the 
reaction? 
(A) 2 
(B) 4 
(C) 
?? ?? 
(D) 
?? ?? 
Ans:  (B) 
A + B ? C + D 
a a 2a 2a at equilibrium 
 ? ?? ?? =
[?? ][?? ]
[A][B]
 =
2a × 2a
a × a
= 4.