When H₂O₂ is shaken with an acidified solution of K₂Cr₂O₇ in the presence of ether, the ethereal layer turns blue due to the formation of

• Cr₂O₃

• ${\mathrm{CrO}}_4^{2-}$

• Cr₂(SO₄)₃

• CrO₅

Anhydrous ferric chloride is prepared by

• dissoving Fe(OH)₃ in concentrated HCl

• dissolving Fe(OH)₃ in dilute HCl

• passing dry HCl over heated iron scrap

• passing dry Cl₂ gas over heated iron scrap

In dilute alkaline solution of MnO${}_4^{-}$ changes to

• MnO${}_4^{2-}$

• MnO₂

• Mn₂O₃

• MnO

34.

Which of the following act as an oxidising agent?

• Np⁴⁺

• Sm²⁺

• Eu²⁺

• Yb²⁺

The compound that is both paramagnetic and coloured is

• K₂Cr₂O₇

• (NH₄)₂ [TiCl₆]

• V₀SO₄

• K₃[Cu(CN)₄]

Transition elements exhibit variable valencies, because they release electrons from the following orbits

• ns

• ns and np

• (n - 1) d and ns

• nd and (n - 1)d

Although zirconium belongs to 4d and hafnium belongs to 5d transition series even they show similar physical and chemical properties because both

• belong to d- block

• have same number of electrons

• belongs to the same group of the periodic table

• have similar atomic radius

Which of the following good reducing agent?

• Yb²⁺

• Ce⁴⁺

• Tb⁴⁺

• La³⁺

Which of the following will not give tests for free transition metal ion in solution ?

• K₂[Ni(CN)₄]

• FeSO₄.K₂SO₄.24H₂O

• Both of the above

• None of the above

Zinc oxide loses oxygen on heating according to the reaction

$\mathrm{ZnO} \stackrel{\mathrm{Heat}}{\to } {\mathrm{Zn}}^{2+} + \frac{1}{2}{\mathrm{O}}_2 + 2{\mathrm{e}}^{-}$

It becomes yellow on heating because

• Zn²⁺ ions and electrons move too interstitial sites and F-centres are created.

• Oxygen and electron moves at the crystal and ions become yellow

• Zn²⁺ again combine with oxygen to give yellow oxide

• Zn²⁺ are replaced by oxygen.