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12th Grade > Chemistry

IONIC EQUILIBRIUM MCQs

Total Questions : 30 | Page 2 of 3 pages
Question 11. If α is the degree of ionization, C the concentration of a weak electrolyte and Ka the acid ionization constant, then the correct relationship between α, C and Ka  is
  1.    α2 = √Ka × C.
  2.    α2 = √CKa
  3.    α = √KaC
  4.    α = √CKa
 Discuss Question
Answer: Option C. -> α = √KaC
:
C
According to the Ostwald's dilution formula α2Ka(1α)C. But for weak
electrolytes αis very small. So that (1α) can be taken as 1. So that α=KaC.
Question 12. NaOH is a strong base because                      
  1.    It gives OH− ion.
  2.    It can be oxidised 
  3.    It can be easily ionised
  4.    It provides H3O+ ions.
 Discuss Question
Answer: Option A. -> It gives OH− ion.
:
A
NaOH completely dissociates to give Na+and OHions in water. Hence it is considered as a Strong base.
Question 13. The dissociation constant of a weak acid is 1.0 × 105. The equilibrium 
constant for the reaction with strong base is 
  1.    1.0 × 10−5
  2.    1.0 × 10−9
  3.    1.0 × 109
  4.    1.0 × 1014
 Discuss Question
Answer: Option C. -> 1.0 × 109
:
C
HAH++A;Ka=[H+][A][HA]….(i)
neutralization of the weak acid with strong base is
HA+OHA+H2O ….(ii)
K=[A][HA][OH]
dividing (i) by (ii) KaK=[H+][OH]=Kw=1014
K=KaKw=1051014=109
Question 14. Which of the following is not a Lewis acid         
  1.    CO
  2.    SiCl4
  3.    SO3
  4.    Zn2+
 Discuss Question
Answer: Option A. -> CO
:
A
CO doesn't have a vacantd-orbital.
Question 15. The solubility in water of a sparingly soluble salt AB2 is 1.0 × 105 mol l1. Its 
solubility product number will be  
  1.    4 × 10−15
  2.    4 × 10−10
  3.    1 × 10−15
  4.    1 × 10−10
 Discuss Question
Answer: Option A. -> 4 × 10−15
:
A
AB2A++2B
At equilibrium, [A+]=1×105,[B]=2×105
Ksp=[1×105][2×105]2=4×1015
Question 16. Equal volumes of 10%vv of HCl is mixed with 10%vv NaOH solution. If density pure NaOH is 1.5 times that of pure HCl then the resultant solution be
  1.    Basic
  2.    Neutral
  3.    Acidic
  4.    Can't be predicted
 Discuss Question
Answer: Option A. -> Basic
:
A
HCl = d
NaOH = 1.5 d
HCl in 10 ml of it = 10d36.5
NaOH in 10 ml of it =10×1.5d40= 15d40
NaOH> HCl
Question 17. A white substance having alkaline nature in solution is 
  1.    NaNO3
  2.    NH4Cl
  3.    Na2CO3
  4.    Fe2O3
 Discuss Question
Answer: Option C. -> Na2CO3
:
C
Na2CO3+2H2O2NaOH+H2CO3
Question 18. Lewis acid
  1.    necessarily has H atoms.
  2.    Is a electron pair donor
  3.    Is always a proton donor
  4.    Is a electron pair acceptor
 Discuss Question
Answer: Option D. -> Is a electron pair acceptor
:
D
Lewis acids accept electron pairs
Question 19. Which of the following is the strongest acid ? 
  1.    H2SO3
  2.    H2SO4
  3.    HClO4
  4.    H3PO4
 Discuss Question
Answer: Option C. -> HClO4
:
C
It is a HClO4
Question 20. For two acids A and B, pKa = 1.2, pKb = 2.8  respectively in value, then which of the following
is true       
  1.    A and B both are equally acidic
  2.    A is stronger than B
  3.    B is stronger than A
  4.    Neither A nor B is strong
  5.    None of the options are correct.
 Discuss Question
Answer: Option B. -> A is stronger than B
:
B
The value of pKafor strong acid is less.

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