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 Multiple Choice QuestionsMultiple Choice Questions

1.

For the reaction,

SO subscript 2 space left parenthesis straight g right parenthesis space plus space 1 half space straight O subscript 2 space left parenthesis straight g right parenthesis space leftwards harpoon over rightwards harpoon space SO subscript 3 space left parenthesis straight g right parenthesis
if Kp = Kc (RT)x where the symbol has usual meaning then the value of x is (assuming ideality)

  • -1

  • -1/2

  • 1/2

  • 1


B.

-1/2

For  the given reaction, ∆ng = np-nR
where np = number of moles of products
nR = number of moles of reactants
Kp = Kc (RT)∆ng

∆ng = -1/2

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2.

In aqueous solution the ionization constants for carbonic acid are
K1 = 4.2 x 10-7 and K2 = 4.8 x 10-11.
Select the correct statement for a saturated 0.034 M solution of the carbonic acid.

  • The concentration of CO32- is 0.034 M

  • The concentration of CO32- is greater than that of HCO3-

  • The concentration of H+ and HCO3- are approximately equal

  • The concentration of H+ is double that of CO32-


C.

The concentration of H+ and HCO3- are approximately equal

straight H subscript 2 CO subscript 3 space rightwards harpoon over leftwards harpoon with space on top space straight H to the power of plus space plus space HCO subscript 3 superscript minus space semicolon space straight K subscript 1 space equals space 4.2 space straight x space 10 to the power of negative 7 end exponent
HCO subscript 3 superscript minus space rightwards harpoon over leftwards harpoon with space on top space straight H to the power of plus space plus space CO subscript 3 superscript 2 minus end superscript space semicolon space straight K subscript 2 space equals space 4.8 space straight x space 10 to the power of negative 11 end exponent
straight K subscript 1 space greater than greater than space straight K subscript 2
therefore space left square bracket straight H to the power of plus right square bracket space equals space left square bracket HCO subscript 3 superscript minus right square bracket semicolon space straight K subscript 2 space equals space fraction numerator left square bracket straight H to the power of plus right square bracket left square bracket CO subscript 3 superscript 2 minus end superscript right square bracket over denominator left square bracket HCO subscript 3 superscript minus right square bracket end fraction
So comma space left square bracket CO subscript 3 superscript 2 minus end superscript right square bracket space equals space straight K subscript 2 space equals space 4.8 space straight x space 10 to the power of negative 11 end exponent
Second dissociation constant is much smaller than the first one. Just a small fraction of total HCO3- formed will undergo the second stage of ionization. Hence in a saturated solution.
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3.

The correct order of increasing basicity of the given conjugate bases (R = CH3) is

  • RCO straight O with minus on top space less than space HC space identical to space straight C with minus on top space less than thin space straight N with minus on top straight H subscript 2 space less than straight R with minus on top
  • RCO straight O with minus on top space less than thin space HC space identical to straight C with minus on top space less than space thin space straight R with minus on top less than space straight N with minus on top straight H subscript 2
  • straight R with minus on top space less than HC space identical to space straight C with minus on top space less than space RCO straight O with minus on top space less than space straight N with minus on top straight H subscript 2
  • RCO straight O with minus on top space less than space straight N with minus on top straight H subscript 2 space less than HC space identical to straight C with minus on top space less than thin space straight R with minus on top

A.

RCO straight O with minus on top space less than space HC space identical to space straight C with minus on top space less than thin space straight N with minus on top straight H subscript 2 space less than straight R with minus on top

Stronger acid has a weaker conjugate base.
Order of acidity : RCOOH > CH≡CH > NH3 > RH

Order of basicity : RCO straight O with minus on top space less than space HC space identical to space straight C with minus on top space less than thin space straight N with minus on top straight H subscript 2 space less than straight R with minus on top 

423 Views

4.

Three reactions involving H2PO4- are given below
I. H3PO4 + H2O → H3O+ + H2PO4-
II. H2PO4- + H2O→ HPO42- + H3O+
III. H2PO4- + OH- → H3PO4  + O2-
In which of the above does H2PO4- act  as an acid

  • (II) only

  • (I) and (II)

  • (III) only

  • (I) only


A.

(II) only

389 Views

5.

At 25°C, the solubility product of Mg(OH)2 is 1.0 × 10–11. At which pH, will Mg2+ ions start precipitating in the form of Mg(OH)2 from a solution of 0.001 M Mg2+ ions?

  • 9

  • 10

  • 11

  • 8


B.

10

straight K subscript sp space equals space left square bracket Mg to the power of 2 plus end exponent right square bracket left square bracket OH to the power of negative 1 end exponent right square bracket squared
left square bracket OH to the power of minus right square bracket squared space equals space straight K subscript sp
left square bracket Mg to the power of 2 plus end exponent right square bracket space equals space 10 to the power of negative 11 end exponent over blank
left square bracket OH to the power of minus right square bracket space equals space 10 to the power of negative 4 end exponent
left square bracket straight H to the power of plus right square bracket space equals space 10 to the power of negative 14 end exponent over 10 to the power of negative 4 end exponent space equals space 10 to the power of negative 10 end exponent
pH space equals space 10 space
342 Views

6.

Consider the reaction:
Cl2(aq) + H2S(aq) → S (s) + 2H+ (aq) + 2Cl- (aq)
The rate equation for this reaction is
I. Cl2 + H2S → H+ +Cl- + Cl+ +HS-
II. H2S ⇌ H+ + HS- (fast equilibrium)
Cl2 + HS- → 2Cl- + H+ + S (slow)

  • II only

  • Both (I) and (II)

  • Neither (I) nor (II)

  • (I) only


D.

(I) only

For (A)
rate = K[Cl2] [H2S]
For (B)
rate = K[Cl2] [HS-] … (i)
putting space in space equation space left parenthesis straight i right parenthesis
rate space equals space straight K left square bracket Cl subscript 2 right square bracket space Keq space fraction numerator left square bracket straight H subscript 2 straight S right square bracket over denominator left square bracket straight H to the power of plus right square bracket end fraction

336 Views

7.

The pH of a 0.1 molar solution of the acid HQ is 3. The value of the ionisation constant, Ka of this acid is

  • 3 x 10–1

  • 1 x 10–3

  • 1 x 10—5

  • 1 x 10–7


C.

1 x 10—5

HQ = H+ + Q-

left square bracket straight H to the power of plus right square bracket space equals space square root of straight K subscript straight a straight C end root space by space ostwald apostrophe straight s space dilution space law
left square bracket straight H to the power of plus right square bracket space equals space 10 to the power of negative pH end exponent space equals space 10 to the power of negative 3 end exponent space straight M
straight C space equals space 0.1 space straight M
Thus comma space 10 to the power of negative 3 end exponent space equals space square root of straight K subscript straight a space straight x 0.1 end root
10 to the power of negative 6 end exponent space equals space straight K subscript straight a space straight x space 0.1
straight K subscript straight a space equals space 10 to the power of negative 5 end exponent

705 Views

8.

The species which can best serve as an initiator for the cationic polymerization is

  • LiAlH4

  • HNO3

  • AlCl3

  • BaLi


C.

AlCl3

Electron-deficient species (Lewis acid) like AlCl3, BF3, etc, are is used as an initiator for cationic polymerisation.

343 Views

9.

The equilibrium constant (Kc) for the reaction, N2(g) + O2 (g) → 2NO (g) at temperature T is 4 x 10-4. The value of Kc for the reaction NO space left parenthesis straight g right parenthesis space rightwards arrow 1 half space straight N subscript 2 space left parenthesis straight g right parenthesis space plus 1 half straight O subscript 2 space left parenthesis straight g right parenthesis at the same temperature is

  • 0.02

  • 2.5 x 102

  • 4 x 10-4

  • 50.0


D.

50.0

straight N subscript 2 space left parenthesis straight g right parenthesis space plus space straight O subscript 2 space left parenthesis straight g right parenthesis space rightwards arrow space 2 NO space left parenthesis straight g right parenthesis
straight K subscript straight c space equals space fraction numerator left square bracket NO right square bracket squared over denominator left square bracket straight N subscript 2 right square bracket left square bracket straight O subscript 2 right square bracket end fraction space equals space 4 space straight x 10 to the power of negative 4 end exponent
2 space NO left parenthesis straight g right parenthesis space rightwards arrow space straight N subscript 2 space left parenthesis straight g right parenthesis space plus space straight O subscript 2 space left parenthesis straight g right parenthesis
straight K subscript straight c apostrophe space equals space 1 over straight K subscript straight c space equals space fraction numerator left square bracket straight N subscript 2 right square bracket left square bracket straight O subscript 2 right square bracket over denominator left square bracket NO subscript 2 right square bracket end fraction space equals space fraction numerator 1 over denominator space 4 space straight x 10 to the power of negative 4 end exponent end fraction space equals space 10 to the power of 4 over 4
NO space left parenthesis straight g right parenthesis space rightwards arrow 1 half space straight N subscript 2 space left parenthesis straight g right parenthesis space plus space 1 half space straight O subscript 2 space left parenthesis straight g right parenthesis
straight K subscript straight c apostrophe apostrophe space equals space fraction numerator left square bracket straight N subscript 2 right square bracket to the power of 1 divided by 2 end exponent left square bracket straight O subscript 2 right square bracket over denominator left square bracket NO subscript 2 right square bracket squared end fraction
space equals space square root of straight K subscript straight c apostrophe end root space equals space square root of 10 to the power of 4 over 4 end root
space equals space 100 over 2 space equals space 50
1948 Views

10.

The equilibrium constant at 298 K for a reaction A+B ⇌ C+D is 100. If the initial concentration of all the four species were 1 M each, then equilibrium concentration of D (in mol L−1 ) will be:

  • 0.818

  • 1.818

  • 1.182

  • 0.182


B.

1.818

space space space space space space space space space space space space space space space space space space space space space straight A space space space space space space plus space space space straight B space rightwards harpoon over leftwards harpoon for space space space space space space space space space of space straight C space space plus space space space space space straight D
subscript Intially space at space straight t space equals 0 space space space space space space space space 1 space space space space space space space space space space space space space space space space 1 space space space space space space space space space space space space space space space space space space space 1 space space space space space space space space space space space space space space space 1 end subscript
to the power of at space equilibrium space space space space space space space 1 minus straight x space space space space space space space space space space 1 minus straight x space space space space space space space space space space space space space space space 1 plus straight x space space space space space space space space space space space 1 plus straight x end exponent
straight K subscript eq space equals space fraction numerator left square bracket CD right square bracket over denominator left square bracket straight A right square bracket left square bracket straight B right square bracket end fraction space equals fraction numerator left parenthesis 1 plus straight x right parenthesis left parenthesis 1 plus straight x right parenthesis over denominator left parenthesis 1 minus straight x right parenthesis left parenthesis 1 minus straight x right parenthesis end fraction space equals space fraction numerator left parenthesis 1 plus straight x right parenthesis squared over denominator left parenthesis 1 minus straight x right parenthesis squared end fraction
Or space 100 space equals space open parentheses fraction numerator 1 plus straight x over denominator 1 minus straight x end fraction close parentheses squared
10 space equals space fraction numerator 1 plus straight x over denominator 1 minus straight x end fraction
or space 10 minus 10 straight x space equals space 1 space plus space straight x
10 minus 1 space space equals space straight x space plus space 10 straight x
9 space equals space 11 space straight x
straight x space equals space 9 over 11 space equals space 0.818 space
left square bracket straight D right square bracket space equals space 1 space plus straight x space equals space 1 space plus space 0.818 space equals space 1.818 space space space
545 Views