When KMnO₄ solution is added to oxalic acid solution, the decolourisation is slow in the beginning but becomes instantaneous after some time because
(a) CO₂ is formed as the product.
(b) The reaction is exothermic.
(c) MnO₄⁻ catalyses the reaction.
(d) Mn²⁺ acts as an auto-catalyst.
(a) CO₂ is formed as the product.
(b) The reaction is exothermic.
(c) MnO₄⁻ catalyses the reaction.
(d) Mn²⁺ acts as an auto-catalyst.
(d) Mn²⁺ acts as auto-catalyst.
Explanation : When KMnO4 solution is added to oxalic acid solution, the decolourisation is slow in the beginning but becomes instantaneous after
sometime because Mn²⁺ acts as an auto-catalyst. Reduction half-reaction :
[MnO₄⁻ + 8H⁺ + 5e⁻ → Mn²⁺ + 4H₂O] × 2
Oxidation half-reaction :
[CO₂⁻ → 2CO + 2e⁻] × 5
Overall equation :
2MnO₄⁻ + 16H⁺ + 5CO₂⁻ → 2Mn²⁺ + 10CO₂ + 8H₂O
End point of this reaction : Colourless to light pink.
Explanation : When KMnO4 solution is added to oxalic acid solution, the decolourisation is slow in the beginning but becomes instantaneous after
sometime because Mn²⁺ acts as an auto-catalyst. Reduction half-reaction :
[MnO₄⁻ + 8H⁺ + 5e⁻ → Mn²⁺ + 4H₂O] × 2
Oxidation half-reaction :
[CO₂⁻ → 2CO + 2e⁻] × 5
Overall equation :
2MnO₄⁻ + 16H⁺ + 5CO₂⁻ → 2Mn²⁺ + 10CO₂ + 8H₂O
End point of this reaction : Colourless to light pink.
Explain the following :
(i) The enthalpies of atomization of transition metals are quite high.
(ii) The transition metals and many of their compounds act as good catalysts.
When Cu²⁺ ion is treated with KI, a white precipitate is formed. Explain the reaction with the help of chemical equation.
Describe the preparation of potassium permanganate. How does the acidified permanganate solution react with oxalic acid ?
Write the ionic equations for the reactions.
The magnetic moment is associated with its spin angular momentum and orbital angular momentum. Spin only magnetic moment value of Cr³⁺ ion is
(a) 2.87 BM
(b) 3.87 BM
(c) 3.47 BM
(d) 3.57 BM
Explain the following observations:
(i) Copper atom has completely filled d orbitals (3d¹⁰) in its ground state, yet it is regarded as a transition element.
(ii) Cr²⁺ is a stronger reducing agent than Fe²⁺ in aqueous solution.
Suggest reasons for the following features of transition metal chemistry :
(i) The transition metals and their compounds are usually paramagnetic.
(ii) The transition metals exhibit variable oxidation states.
Describe the oxidising action of potassium dichromate and write the ionic equations for its reaction with (i) an iodide (ii) H₂S.
When Xe reacts with Fluorine in 1:5 ratio at 873 K it forms
a) \(XeF_2\)
b) \(XeF_4\)
c) \(XeF_6\)
d) \(XeOF_4\)
Aryl halides can not be prepared by the reaction of arylalcohols with \(PCl_3\), \(PCl_5\) or \(SOCl_2\) because :
(a) phenols are highly stable compounds.
(b) carbon-oxygen bond in phenols has a partial doublebond character.
(c) carbon-oxygen bond is highly polar
(d) all of these
Although Zirconium belongs to 4d transition series and Hafnium to 5d transition series even then they show similar physical and chemical properties because
(a) both belong to d-block.
(b) both have same number of electrons.
(c) both have similar atomic radius.
(d) both belong to the same group of the periodic table.
The electronic configuration of Cu(II) is 3d⁹ whereas that of Cu(I) is 3d¹⁰. Which of the following is correct?
(a) Cu(II) is more stable
(b) Cu(II) is less stable
(c) Cu(I) and Cu(II) are equally stable
(d) Stability of Cu(I) and Cu(II) depends on nature of copper salts
The functional group which is found in amino acid is-
(a)-COOH
(b) -\(NH_2\)
(c) -\(CH_3\)
(d) both (a) and (b)
Which of the following is an example of vic-dihalide?
(a) Dichloromethane.
(b) 1,2-dichloroethane.
(c) Ethylidene chloride.
(d) Allyl chloride.