In aqueous solution the ionization constants for carbonic acid a

Subject

Chemistry

Class

JEE Class 12

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 Multiple Choice QuestionsMultiple Choice Questions

1.

The standard enthalpy of formation of NH3 is– 46.0 kJmol–1. If the enthalpy of formation of H2 from its atoms is – 436 kJ mol–1 and that of N2 is – 712 kJ mol–1,the average bond enthalpy of N – H bond is NH3 is

  • -964 kJ mol-1

  • +352 kJ mol-1

  • +1056 kJ mol-1

  • +1056 kJ mol-1

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2.

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)

  • Neither (I) nor (II)

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3.

If 10–4 dm3 of water is introduced into a 1.0 dm3 flask at 300 K, how many moles of water are in the vapour phase when equilibrium is established?(Given: Vapour pressure of H2O at 300 K is 3170 Pa; R = 8.314 J K–1 mol–1)

  • 5.56 x 10-3 mol

  • 1.53 x 10-2 mol

  • 4.46 x 10-2 mol

  • 4.46 x 10-2 mol

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4.

The energy required to break one mole of Cl— Cl bonds in Cl2 is 242 kJ mol. The longest wavelength of light capable of breaking a single Cl — Cl bond is
(c= 3 x 108 ms–1and NA = 6.02 x 1023 mol–1)

  • 594 nm

  • 640 nm

  • 700 nm

  • 700 nm

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5.

The ionization energy of He+ is 19.6 x 10–18 J atom–1. The energy of the first stationary state (n = 1) of Li2+ is

  • 4.41 x 10-16 J atom–1

  • -4.41 x 10-17 J atom–1

  • -2.2 x 10-15 J atom–1.

  • -2.2 x 10-15 J atom–1.

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6.

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

  • (III) only

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7.

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+ and HCO3- are approximately equal


C.

The concentration of H+ and HCO3- are approximately equal


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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8.

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
  • 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
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9.

The correct sequence which shows decreasing order of the ionic radii of the elements is

  • Al3+ > Mg2+ > Na+ > F- > O2-

  • Na+ > Mg2+ > Al3+ > O2- > F-

  • Na+ > F- > Mg2+ > O2- > Al3+

  • Na+ > F- > Mg2+ > O2- > Al3+

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10.

The solubility product of silver bromide is 5.0 x 10-13. The quantity of potassium bromide (molar mass taken as 120 g mol–1)to be added to 1 litre of 0.05 M solution of silver nitrate to start the precipitation of AgBr is

  • 1.2 x 10-10

  • 1.2 x 10-9 g

  • 6.2 x 10-5

  • 6.2 x 10-5

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