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NEET Chemistry MCQ
Chemical And Ionic Equilibrium Mcq
Quiz 2
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Q.1
The equilibrium constant for reversible reaction N2 + 3H2 ⇔ 2NH3 is K and for the reaction ½ N2 + (3/2)H2 ⇔ NH3 The equilibrium constant is K'. K and K' will be related as [ MP CET 1998]
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a) K=K'
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b) K'=√(K)
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c)K=√(K')
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d)K × K'=1
Explanation
Equilibrium constant is independent of the initial concentration. It varies with temperature only If equilibrium constant is K for reaction A + B ⇋ C + D If equilibrium constant is K' for reaction n(A+B) ⇋ n(C+D) Then K' = Kn ∴ K' = K1/2 Answer: (b)
Q.2
Which oxide of nitrogen is most stable at 273 K ?
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a)
0%
b)
0%
c)
0%
d)
Explanation
Value of K gives an idea about the extent of reaction. Larger the value of K, more is the extent of reaction. NO2. with the least value of K is dissociated to least extent among the given oxides Answer:(d)
Q.3
The equilibrium constant for reaction SO3 → SO2 + ½O2 is Kc=4.9 × 10-the value of Kc for the reaction 2SO2 + O2 → 2SO3 will be [ AIEEE 2006]
0%
a) 416
0%
b) 2.4 × 10-3
0%
c) 9.8 × 10-2
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d) 4.9× 10-2
Explanation
For reaction SO3 → SO2 + ½O2 For reactionSO2 + ½O2 → SO3 For reaction 2SO2 + O2=2SO3 Answer: (a)
Q.4
the equilibrium constant Kp for the reaction PCl5 ↔ PCl3 + Cl2 is 16 If the volume of the container is reduced to half of its original volume, the value of Kp for the reaction at the same temperature will be
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a)32
0%
b) 64
0%
c)16
0%
d)4
Explanation
Equilibrium constant is independent of initial concentration. It varies with temperature onlyAnswer: (c)
Q.5
For a reaction N2 + 3 H2 → 2NH3; °H=-22 kcal. If energy of activation for this reaction is 70 kcal, the energy of activation for backward reaction is
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a) 70 kcal
0%
b) 92 kcal
0%
c)48 kcal
0%
d)None of these
Explanation
Backward reaction is endothermic Δ H=Ea(forward) - Ea(backward) Ea(backward)=70 +2 0=92 kcalAnswer: (b)
Q.6
the value of reaction quotient before any reaction occurs is
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a) ∞
0%
b) -1
0%
c)0
0%
d)1
Explanation
Before occurrence of reaction only reactants are present in the reaction mixture. Concentration of product is zero Answer:(c)
Q.7
Consider the following equilibrium in closed container N2O4 ⇔ 2NO2 . At a fixed temperature, the volume of the reaction container is halved. For this change, which of the following statement holds true regarding the equilibrium constant (Kp) and degree of dissociation ( α) [ IIT 2002]
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a) Neither Kp nor α changes
0%
b) Both Kp nor α changes
0%
c) Kp changes but α does not change
0%
d) Kp does not change but α changes
Explanation
At constant temperature, equilibrium constant Kp does not change. By decreasing volume at constant temperature, pressure is increased which shifts the equilibrium in the direction in which number of moles decreases. i.e. backward direction. Since direction of equilibrium is changed, degree of dissociation α would also change Answer: (d)
Q.8
For reaction Co + K2O ⇔ Co2 + H2 at given temperature, the equilibrium amount of CO2 can be increased by [ IIT 1998]
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a)Adding a suitable catalyst
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b) Adding an inert gas
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c)Decreasing the volume of the container
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d)Increasing the amount of CO
Explanation
Increase in concentration of one of the reactants shifts the equilibrium in direction in which that reactant is consumed. i.e in forward direction to produce more of productsAnswer: (d)
Q.9
The yields of NH3 in the reaction N2 + 3H2 ↔ 2NH3 ; ΔH=-22.08 kcal is affected by [ Pb CET 1997]
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a) Change in pressure and temperature
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b) Change in temperature and concentration of H2
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c)Change in pressure and concentration of N2
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d)Change in pressure, temperature and concentration of N2
Explanation
option 'd' by Le Chatelier principleAnswer: (d)
Q.10
If 1.0 mole of I2 is introduced into 1.0 litre flask at 1000K which leads to dissociation, at equilibrium, ( Kc=10-6), which one is correct?
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a) [ I2(g)] > I-]
0%
b) [ I2(g)] < I-]
0%
c) [ I2(g)]=I-]
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d) [ I2(g)]=½ I-]
Explanation
Equilibrium constant has no effect of pressure, it depends on temperature only The reaction takes place as follows I2( g) ⇋ 2I (g), Kc=10-6 Clearly, the equilibrium constant favours I2( g) Answer:(a)
Q.11
At constant temperature, the equilibrium constant ( Kp) for the decomposition reaction N2O4 ⇔ is expressed by Kp=4x2P/(1-x2) where P is pressure, x is extent of decomposition. Which of the following statement is true [ IIT 2001]
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a) Kp increases with increase with increase of P
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b) Kp increases with increase with increase of x
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c) Kp increases with decrease with increase of P
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d) Kp remains constant with change in P or x
Explanation
Kp changes only with temperature Answer: (d)
Q.12
Four species are listed below (i) HCO3- (ii) H+ (iii) HSO4- (iv) HSO3F Which one of the following is the correct sequence of their acid strength [ AIEEE 2008]
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a) iii < i < iv < ii
0%
b) iv < ii < iii < i
0%
c)ii < iii < i < iv
0%
d)i < iii < ii < iv
Explanation
HSO3F is super acid, hence strongest among all. We know weaker the conjugate base stronger the acid Answer: (d)
Q.13
Among the following acids, which has the lowest pKa value?
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a) CH3COOH
0%
b) HCOOH
0%
c)(CH3)2CHOOH
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d)CH3CH2COOH
Explanation
Strong acid have lower pKa valueAnswer: (b)
Q.14
Which of the following bases is the weakest?
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a) C9H7N : Kb=6.3 ×10-10
0%
b) C2H5NH2 : Kb=5.6 ×10-4
0%
c) C6H5NH2 : Kb=3.8 ×10-10
0%
d)NH4OH : Kb=1.6 ×10-6
Explanation
Greater the value of Kb of a base stronger the base Answer:(c)
Q.15
A solution which is 10-3 M each in Mn2+, Fe2+, Zn2+ and Hg2+ is treated with 10-16M sulphide ion. If Ksp of MnS, FeS, ZnS and HGS are 10-15,10-23, 10-20 and 10-54 respectively, which one will precipitate first.. [ IIT 2003]
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a) FeS
0%
b) MnS
0%
c) HgS
0%
d) ZnS
Explanation
MS ⇔ M2+ + S2- Lower the value of Ksp lower will be the solubility. Thus HgS with least value of Ksp will get precipitated first Answer: (c)
Q.16
On adding 0.1M solution each of [Ag+], [Ba2+], [Ca2+] in a Na2SO4 solution, species first precipitated is [Ksp of BaSO4=10-11, Ksp of CaSO4=10-6, Ksp of Ag2SO4=10-5]
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a)Ag2SO4
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b) BaSO4
0%
c)CaSO4
0%
d)All of these
Explanation
Salt with least value of Ksp will precipitate firstAnswer: (b)
Q.17
Precipitation takes place when the ionic product [ Roorkee 1983]
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a) Equals the solubility product
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b) Exceeds the solubility product
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c)Is less than the solubility product
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d)Is almost zero
Explanation
Answer: (b)
Q.18
At 25°C, the dissociation constant of Ch3COOH and NH4OH in aqueous solution are almost same ( 10-5). If pH of some acetic acid solution is 3.0 The pH of solution of NH4OH of same concentration at the same temperature would be [ Roorkee 1990]
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a) 3.0
0%
b) 4.0
0%
c)10.0
0%
d)11.0
Explanation
pH of CH3COOH=3 [H+]=10-3M or [CH3COOH]=10-3 M ∴ [OH-]=10-3 M But [H+] [ OH-]=10-14 ∴ [H+]=10-11 M ∴ pH of NH4OH solution=-log10-11=11 Answer:(d)
Q.19
When 0.1 mol of CH3NH2 ( ionization constant,Kb=5 ×10-4) is mixed with 0.08 mol HCl and the volume is maid up toFind the [H+] of resulting solution. [ IIT 2005]
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a) 8 × 10-5
0%
b) 2 × 10-11
0%
c) 1.23 × 10-4
0%
d) 8 × 10-11
Explanation
Resulting solution contains [salt]=0.08 and [base]=0.1 - 0.08=0.02 Now pKb=-logKb pKb=3.3 pH + pOH=14 pH=140- 3.90=10.1 Applying pH=-log[H+] 10.1=-log [ H+] taking antilog Antilog [ -11 + 0.9]=H+H+=8 ×10-11 Answer: (d)
Q.20
Species acting both as Bronsted acid and base is
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a)HSO4-
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b) Na2CO3
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c)NH3
0%
d)OH-
Explanation
According to bronsted_lowry concept, an acid is a substance that can donate and a base is substance that can accept a proton from acid.HSO4- can accept a proton and form H2SO4 as well as can donate a proton and form SO42-Answer: (a)
Q.21
The pH of 0.1M aqueous solution of weak acid ( HA) isIts degree of dissociation is
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a) 1%
0%
b) 10%
0%
c)50%
0%
d)25%
Explanation
HA ⇔ H+ + A- Sin pH=3 [H+]=Cα=10-3 ∴ 0.1 × α=10-3 Or α=10-2 Or 1%Answer: (a)
Q.22
An acid buffer solution can be prepared by mixing equimolar amount of ..[ IIT 1981]
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a) Formic acid and sodium formate
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b) NH4Cl and NH4OH
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c)H2SO4 and NA2SO4
0%
d)CH3CONH2 and KOH
Explanation
Weak acid + salt of weak acid with strong base=acidic buffer Answer:(a)
Q.23
pKa of acetic acid is 4.The concentration of CH3COONa is 0.01 M. The pH of CH3COONa ia [ Orissa JEE 2004]
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a) 8.37
0%
b) 4.37
0%
c) 4.74
0%
d) 0.474
Explanation
CH3COONa is a salt of weak acid (CH3COOH) and strong base (NaOH) Applying pH=½ [ pKw + pKa + logC] pH=½ [ 14 +4.74 + log10-2]=8.37 Answer: (a)
Q.24
In a saturated solution of the sparingly soluble strong electrolyte AgIO3 molecular mass=283, the equilibrium which sets in is AgIO3 ⇔ Ag+ + IO3- If the solubility product constant Ksp of AgIO3 at given temperature is 1.0 ×10-8, what is the mass of AgIO3 contained in 100 ml of its saturated solution [ AIEEE 2007]
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a)1.0 ×10-4 g
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b) 28.3 ×10-2 g
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c)2.83 ×10-3 g
0%
d)1.0 ×10-7 g
Explanation
AgIO3 ⇔ Ag+ + IO3- s=solubility ∴ Ksp=s2 s2=1.0 ×10-8 or s=1.0 × 10-4 mol/L s=1.0 × 10-4 (283) g/L for 100 ml solution s=2.83 ×10-3 g Answer: (c)
Q.25
Which of the following salts undergoes anionic hydrolysis?
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a) CuSO4
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b) Na2CO3
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c)NH4Cl
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d)FeCl3
Explanation
CO3- + 2H2O → H2CO3 + OH-Answer: (b)
Q.26
At 90°C, pure water has H3O+ ion concentration of 10-6 mol/L. the Kw at 90°C is
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a) 10-12
0%
b) 10-14
0%
c)10-6
0%
d)10-8
Explanation
Kw=[ H+] [OH-]Kw=10-6 × 10-6=10-12 Answer:(a)
Q.27
A weak acid HX has the dissociation constant 1 × 10-5M. It forms a salt NaX on reaction with alkali. The degree of hydrolysis of 0.1M solution of NaX is
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a) 0.0001%
0%
b) 0.01%
0%
c) 0.1%
0%
d) 0.15%
Explanation
For a salt of weak acid (HX) and strong base ( NaOH) We know, Percentage degree of hydrolysis=10-4 × 100=10-2 =0.01% Answer: (b)
Q.28
An acidic buffer solution can be prepared by mixing solution of .. [ IIT 1981]
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a)Sodium acetate and acetic acid
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b) Ammonium chloride and ammonium hydroxide
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c)Sulphuric acid and sodium sulphate
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d)Sodium chloride and sodium hydroxide
Explanation
Weak acid + salt of weak acid with strong base=acidic bufferAnswer: (a)
Q.29
The value of ionic product of water at 393K is [ Tamil Nadu CET 2002]
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a) Less than 1 × 10-14
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b) Greater than 1 × 10-14
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c)Equal to 1 × 10-14
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d)Equal to 1 × 10-7
Explanation
Degree of ionization increases with increase of temperature [H+] and [OH-] increases with the rise of temperature and ionic product becomes greater than 1 × 10-14Answer: (b)
Q.30
aht is the decreasing order of strength of the bases:
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a)
0%
b)
0%
c)
0%
d)
Explanation
Conjugate base of strong acid is weak while conjugate base of weak acid is strong. Acidic strength of conjugate acid is Thus Decreasing order of basic strength Answer:(a)
0 h : 0 m : 1 s
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