Which of the following ions forms most stable complex compound?

• Cu²⁺

• Ni²⁺

• Fe²⁺

• Mn²⁺

Pb²⁺, Cu²⁺, Zn²⁺ and Ni²⁺ ions are present in a given acidic solution. On passing hydrogen sulphide gas through this solution the available precipitate will contain

• PbS and NiS

• PbS and CuS

• CuS and ZnS

• CuS and NiS

To an acid solution of an anion a few drops of KMnO₄ solution are added. Which of the following, if present will not decolourise the KMnO₄ soltuion?

• NO${}_2^{-}$

• S^2-

• Cl^-

• CO${}_3^{2-}$

AgNO₃ gives red colour with

• NaCl

• NaBr

• NaI

• K₂CrO₄

Calomel is

• Hg₂Cl₂

• Hg + Hg₂Cl₂

• 

• 

Which of the following complex neutralises three molecules of AgNO₃?

• [Co(NH₃)₆]Cl₃

• [Co(NH₃)₅Cl]Cl₂

• [Co(NH₃)₄Cl₂]Cl

• [Co(NH₃)₃Cl₃]

107.

Elements which generally exhibit multiple oxidation states and whose ions are usually coloured are

• metalloids

• non- metals

• tranistion elements

• gases

The transition metals mostly are

• diamagnetic

• paramagentic

• neither diamagnetic nor paramagnetic

• both diamagnetic and paramagnetic.

The correct statement in respect of d-block elements is

• they are all metals

• they show variable valency

• they form coloured ions and complex salts

• All the above statements are correct

On reduction of KMnO₄, by oxalic acid in acidic medium, the oxidation number of Mn changes. What is the magnitude of this change?

• From 7 to 2

• From 6 to 2

• From 5 to 2

• From 7 to 4