Acidified K₂Cr₂O₇ solution turns green when Na₂SO₃ is added to it. This is due to the formation of

• Cr${\mathrm{O}}_4^{2-}$

• Cr₂(SO₃)₃

• CrSO₄

• Cr₂(SO₄)₃

Which one of the following is 'd-block element?

• Gd

• Hs

• Es

• Cs

Point out the incorrect reaction from the following.

• 2Na₂CrO₄ + H⁺ $\to$ Na₂Cr₂O₇ + 2Na⁺ + H₂O

• 4MnO₂ + 4KOH + O₂ $\to$ 4KMnO₄ + 2H₂O

• 2Mn${\mathrm{O}}_4^{-}$ + 5C₂${\mathrm{O}}_4^{2-}$ + 16H⁺ $\to$ 2Mn²⁺ + 10CO₂ + 8H₂O

• Mn${\mathrm{O}}_4^{-}$ + 8H⁺ + 5Fe²⁺ $\to$5Fe³⁺ + Mn²⁺ + 4H₂O

On addition of small amount of KMnO₄ to conc. H₂SO₄, a green oily compound is obtained which is highly explosive in nature. Identify the compound from the following

• Mn₂O₇

• MnO₂

• MnSO₄

• Mn₂O₃

White P reacts with caustic soda, the products are PH₃ and NaH₂PO₂. This reaction is an example of

• hydrolysis

• reduction

• disproportionation

• neutralisation

The aqueous solution containing which one of the following ions will be colourless ? (Atomic no. Sc= 21, Fe= 26, Ti= 22, Mn = 25)

• Sc³⁺

• Fe²⁺

• Ti³⁺

• Mn²⁺

The main reason for larger number of oxidation states exhibited by the actinides than the corresponding lanthanides, is

• lesser energy difference between 5f and 6d orbitals than between 4f and 5d orbitals

• larger atomic size of actinides than the lanthanide

• more energy difference between 5f and 6d orbitals than between 4f and 5d orbitals

• greater reactive nature of the actinides than the lanthanides

Cr is member of 3d transition series of atomic number 24. What will be its electronic configuration ?

• 3d⁶4s²

• 3d⁵4s²

• 3d⁴4s²

• 3d⁵4s¹

The element ₉₀Th²³² belong to thorium series. Which of the following will act as the end product of the series?

• ₈₂Pb²⁰⁸

• ₈₂Bi²⁰⁹

• ₈₂Pb²⁰⁶

• ₈₂Pb²⁰⁷

240.

Which of the following turns potassium dichromate paper green?

• NO₂

• HCl

• NH₃

• SO₂