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NEET Chemistry MCQ
Quiz 4
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Q.1
Equilibrium constant for the reaction 2NO(g) + Cl2(g) ↔ 2NOCl(g) is correctly given by the expression.. [ CPMT 1983]
0%
a)
0%
b)
0%
c)
0%
d)
Explanation
By the law of chemical equilibriumAnswer: (b)
Q.2
A reaction reaches a state of chemical equilibrium only when ..[Pb CET 1989]
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a) the reactants and the products are reacting
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b) the concentrations of the reactants and the products become equal
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c)the products reacts together at the same rate at which they are formed
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d)all the reactants and the products are in the same state of matter
Explanation
equilibrium is achieve when rate of formed and rate of reverse direction reaction is sameAnswer: (c)
Q.3
Which one of the following information can be obtained on the basis of Le Chatelier principle? [ CBSE PMT 1992]
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a) Dissociation constant of weak acid
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b) Entropy change in a reaction
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c) Equilibrium constant of a chemical reaction
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d) Shift in equilibrium position on changing value of a constraint
Explanation
Answer: (d)
Q.4
The equilibrium constant , K for the reaction 2HI(g) ↔ H2(g) + I2(g) at room temperature is 2.85 and that at 698K, it is 1.4×10-This implies that : [ NCERT 1984]
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a)HI is exothermic compound
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b) HI is very stable at room temperature
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c)HI is relatively less stable than H2 and I2
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d)HI is resonance stabiles
Explanation
Decrease in K with increase in temperature indicates reaction is exothermic if forward direction . AS reaction is exothermic , HI is less stable than H2 and I2Answer: (c)
Q.5
At 500K, the equilibrium constant for reaction cisC2H2Cl2 ↔ transC2H2Cl2 is 0.6At the same temperature, the equilibrium constant for the reactiontransC2H2Cl2 ↔ cisC2H2Cl2
0%
a) 0.66
0%
b) 1.67
0%
cg)0.76
0%
d)2.6
Explanation
For reverse reaction K'=1/K K'=1/0.66=1.67Answer: (b)
Q.6
For the gas phase reaction 2NO ↔ N2 + O2, ΔH=-43.5 kcal mol-1Which one of the statement below is true for N2(g) + O2(g) ↔ 2NO(g) [CPMT 1990]
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a) K is independent of T
0%
b) K increases as T decreases
0%
c)K decreases as T decreases
0%
d)K varies with the addition of NO
Explanation
Second reaction is endothermic thus K decreases as T decreases Answer:(c)
Q.7
In a chemical equilibrium Kc=Kp when ..[Bihar CEE 1992]
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a) the number of molecules entering into the reaction is more than the number of molecules produced
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b) the total number of moles of the reactants equals that of the products
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c) the number of molecules entering into the reaction is the same as the number of molecules produced
0%
d) the number of molecules entering into the reaction is less than the number of molecules produced
Explanation
Answer: (c)
Q.8
In the two gaseous reactions (i) and (ii), at 25°C (i)NO(g) + ½O2(g) ↔ NO2(g), K1 (ii) 2NO2(g) ↔ 2NO(g) + O2(g), K2 the equilibrium constant K1 and K2 are related as ..[CBSE PMT 1994]
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c)K2=1/K12
0%
d)K2=K12
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a)K₂=1/K₁
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b) K₂=K₁/2
Explanation
Reaction (ii) is inverse and double of reaction (i) Hence option'c' is correctAnswer: (c)
Q.9
For a reactionH2 + I2 ↔ 2HI at 721K, the value of equilibrium constant isIf 0.5 moles each of H2 and I2 is added to the system, the value of equilibrium constant will be [ MP 1990]
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a) 0.02
0%
b) 0.2
0%
c) 50
0%
d) 25
Explanation
For given reaction addition of reactant could not affect equilibrium constant as Δng=0, only change in temperature will cause change in equilibrium constant. Since temperature is constant equilibrium constant will will remain 50 Answer: (c)
Q.10
In which of the following, the forward reaction is favoured by use of high pressure ..[AFMC 1994]
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a)H2 + I2 ↔ 2HI
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b) N2 + O2 ↔ 2NO
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c)2NH3 ↔ N2 + 3H2
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d)2SO2 + O2 ↔ 2SO3
Explanation
In option 'd' reactant sides have 3 moles of gases while product side two moles of gases thus on increasing pressure reaction will go in forward direction to reduce pressureAnswer: (d)
Q.11
If K1 and K2 are respective equilibrium constant for the two reactionsXeF6(g) + H2O(g) ↔ XeOF4(g) + 2HF(g)XeO4(g) + XeF6(g) ↔ XeOF4(g) + XeO3F2the equilibrium constant for the reactionXeO4(g) + 2HF(g) ↔ XeO3F3F2(g) + H2O(g)
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a) K1 / K22
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b) K1 . K2
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c)K₁/K₂
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d)K₂/K₁
Explanation
Given reaction is addition of reaction reaction(ii) and reverse of reaction (i) thus option 'd' correctAnswer: (d)
Q.12
In which of the following reaction Kp > Kc
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a)N2 + 2H2 ↔ 2NH3
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b) H2 + I2 ↔ 2HI
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c)PCl3 + Cl2 ↔ PCl5
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d)Na2S2O7 ⇌ Na2SO4 + SO3
Explanation
In option 'd' Δng > 1 Kp = Kc [RT]ng Answer: (d)
Q.13
For a chemical reaction 2A + B ↔ C, the thermodynamic equilibrium constant Kp is [ IAS prelims1999]
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a) in atm-2
0%
b) in atm-3
0%
c)in atm-1
0%
d)dimensionless
Explanation
Answer: (a)
Q.14
1.1 mole of A is mixed with 2.2 mol of B and the mixture is kept in two litre flask till the equilibrium is reached.A +2B ↔ 2C + DAt equilibrium 0.2 mol of C is formed. the equilibrium constant of the above reaction is [ CBSE PMT 1994]
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a) 0.002
0%
b) 0.004
0%
c)0.001
0%
d).003
Explanation
At equilibrium C produced=0.2 moles thus concentration=0.2/2=0.1 mole/lit D produced=0.1 mole concentration=0.1/2=0.05 mole/litre A balance=1.1 - 0.1=1 concentration=1/2=0.5 mole/litre B balance=2.2 -0.2=2, concentration=2/2=1 mole/litre For the formula for equilibrium constant Answer:(c)
Q.15
If the equilibrium constant of the reaction 2HI ↔ H2 + I2 is 0.25, then the equilibrium constant for the reaction H2 + I2 ↔ 2HI would be [ MP PMT 1995]
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a)1
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b) 2
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c)3
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d)4
Explanation
As equilibrium constant for reverse reaction K'=1/ kAnswer: (d)
Q.16
The equilibrium SO2Cl2(g) ↔ SO2(g) + Cl2(g)is attained at 25°C in a closed container and an inert gas, helium is introduced. Which of the following statement is correct? [ MP PMT 2000]
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a) More chlorine is formed
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b) Concentration of SO2 is reduced
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c)More SO2Cl2 is formed
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d)Concentration of SO2Cl2, SO2 and Cl2 do not change
Explanation
Introduction of inert gas do not change equilibrium conditionAnswer: (d)
Q.17
A reaction id A+B ↔ C + D. Initially we start with equal concentration of A and B. At equilibrium we find that the moles of C is two times of A. What is the equilibrium constant of the reaction? [ KCET 2000]
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a) 1/4
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b) 1/2
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c)4
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d)2
Explanation
Concentration of A nd B at equilibrium=aConcentration of C and D at equilibrium=2aFrom formula equilibrium constant=4 Answer:(c)
Q.18
For reaction PCl3(g) + Cl2(g) ↔ PCl56(g),the value of Kc at 250°C isThe value of Kp at this temperature will be [ MLNR 1990]
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a) 0.61
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b) 0.83
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c) 0.57
0%
d) 0.46
Explanation
Δng=1-2=-1 Kp=Kc(RT)Δng Kp=26(0.0821 × 523)-1=0.61 Answer: (a)
Q.19
Steam reacts with iron at high temperature to give hydrogen gas and Fe3O4(s). the correct expression for the equilibrium constant is .. [DEC 1994]
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a)
0%
b)
0%
c)
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d)
Explanation
reaction is 3Fe(s) + 4H2O(g) ↔ Fe3O4(s) + 4H2Take concentration of solid=1, option "b" is correctAnswer: (b)
Q.20
For the reaction PCl5(g) ↔ PCl3(g) + Cl2(g), the forward reaction at constant temperature is favoured by ..[Pb CET 1997]
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a) Introducing an inert gas at constant volume
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b) Introducing PCl3(g) at constant volume
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c)Introducing PCl5(g) at constant volume
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d)Introducing Cl2 (g) at constant volume
Explanation
Answer: (c)
Q.21
A one litre vessel initially contains 2.0, 0.5 and 0.0 moles of N2, H2 and NH3 respectively. the system after attaining equilibrium has 0.2 mole of NHThe number of moles of H2 in the vessel at equilibrium is [ Pb.CET 1990]
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a) 0.3
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b) 0.4
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c)0.2
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d)1.8
Explanation
Equation is N2 + 3H2 ↔ 2NH3When 0.2 moles of ammonia produced consumption of Nitrogen is 0.1 mole and hydrogen is 0.3 mole &There4 balnce of H2 = 0.5-0.3 = 0.2Answer:(a)
Q.22
XY2 dissociates asXY2(g) ↔ XY(g) + Y(g) When the initial pressure of XY2 is 600mm Hg, the total equilibrium pressure is 800mmHg. Calculate K for the reaction assuming that the volume of system remains unchanged ..[BHU 1992]
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a) 50
0%
b) 100
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c) 166.6
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d) 400
Explanation
let p be the pressure of XY(g) and Y(g) each then pressure of reactant at equilibrium is 600-p Now total pressure at equilibrium is 800=[(600-p) + p + p] p=200 from equation Answer: (b)
Q.23
For the chemical reaction3X(g) + Y(g) ↔ X3Y(g)the amount of X3Y at equilibrium is affected by ..[IIT 1999]
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a) temperature and pressure
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b) pressure only
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c)temperature only
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d)temperature, pressure and catalyst
Explanation
Answer: (a)
Q.24
A quantity of Pcl5 was heated in a 10 litre vessel at 250°C. It dissociates as PCl5(g) ↔ PCl3(g) + Cl2(g)At equilibrium the vessel contains 0.1 mol of PCl5, 0.20 mole of PCl3 and 0.20 mole of ClThe equilibrium constant of the reaction is ..[KCET 1993]
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a)0.02
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b)0.05
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c)0.04
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d)0.025
Explanation
Use formula for equilibrium constant Answer:(c)
Q.25
One mole of a compound AB reacts with one mole of compound CD according to the equatingAB + CD ↔ AD + CB. When equilibrium had been established it was found that 3/4 mole each of reactants AB and CD has been converted to AB and CD. There is no change in volume. The equilibrium constant of the reaction is ..[Kerala MEE 2003]
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a) 9/16
0%
b) 1/9
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c) 16/9
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d) 9
Explanation
If initial concentration of AB and CD is a then at equilibrium concentrations are AB and CD=a/4AD and CB=3a/4 For formula of equilibrium constant K=9 Answer: (d)
Q.26
In which manner will increase of pressure affect the following equation? C(s) + H2O(g) ↔ CO(g) + H2O ..[IIT 1994]
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a)Shift in the forward direction
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b) Shift in the reverse direction
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c)Increases in the yield of hydrogen
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d)No effect
Explanation
According to Le Chatelier principle. To reduce pressure reaction will go in reverse directionAnswer: (b)
Q.27
Which of the following equilibrium will shift to right side on increasing the temperature? [ MP PMT 2000]
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a) CO(g) + H2O(g) ↔ SO2(g) + Cl2(g)
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b) 2SO2(g) + O2(g) ↔ 2SO3(g)
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c)H2O(g) ↔ H2(g) + ½ O2(g)
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d)4HCl(g) + O2(g) ↔ 2H2O(g) + 2Cl2(g)
Explanation
Equation 'c' is endothermic Answer: (c)
Q.28
At certain temperature only 50% HI is dissociated into H2 and I2 at equilibrium. the equilibrium constant is ..[KCET 1994]
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a) 1.0
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b) 3.0
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c)0.5
0%
d)0.25
Explanation
2HI ↔ H2 + I2Initial concentration of HI=a, concentration at equilibrium is a/2then concentration of H2 and I2 is a/4Thus equilibrium constant is 0.25 Answer:(c)
Q.29
1 mole of hydrogen and 2moles of iodine are taken initially in a 2litre vessel. the number of moles of hydrogen at equilibrium is 0.Then the number of moles of iodine and hydrogen iodide at equilibrium are [ Tamil nadu CET 2002]
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a) 1.2, 1.6
0%
b) 1.8, 1.0
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c) 0.4, 2.4
0%
d) 0.8, 2.0
Explanation
At equilibrium number of moles of Hydrogen=1-0.8=0.2Iodine=2-0.8=1.2Hydrogen bromide=2×0.8=1.6 Answer: (a)
Q.30
In the Haber process for the industrial manufacture, of ammonia involving the reaction N2 + 3H2 ↔ 2NH3 at 200 atm pressure in presence of a catalyst, a temperature of about 500°C is used. This is considered as optimum temperature for the process because
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a)Yield is maximum at this temperature
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b) Catalyst is active only at this temperature
0%
c)energy needed for the reaction is easily obtained at this temperature
0%
d)rate of the catalytic reaction is fast enough while the yield is also appreciable for this exothermic reaction at this temperature
Explanation
Answer: (d)
0 h : 0 m : 1 s
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