The reaction between metallic silver and aqueous NaCN forming a soluble complex occurs in the presence of :

• nitrogen

• oxygen

• helium

• chlorine

252.

Which one is colourless ?

• Co²⁺

• Ni²⁺

• Fe³⁺

• Cu⁺

In first transition series, which element show maximum oxidation states :

• Co

• Mn

• Cr

• Fe

The most paramagenetic is :

• Cr³⁺

• Co²⁺

• Mn²⁺

• Fe²⁺

The diamagnetic species is

• [Ni(CN)₄]^2-

• [Ni(Cl)₄]^2-

• [CoCl]^2-

• [CoF₆]^3-

Enrichment of U²³⁵ is done by

• IF₇

• CIF₃

• IF₃

• ClF₅

Colour imparted by Co(II) compounds to glass is

• green

• brown

• violet

• blue

In presence of acidic medium, KMnO₄ converts H₂S into

• Mn only

• MnS only

• MnS + S

• S only

Lanthanides and actinides are also called :

• short periods

• inner-transition elements

• long periods

• main transition elements

Assertion : Fe³⁺ can be used for coagulation of As₂S₃ sol.

Reason : Fe³⁺ reacts with As₂S₃ to give Fe₂S₃.

• If both assertion and reason are true and reason is the correct explanation of assertion.

• If both assertion and reason are true but reason is not the correct explanation of assertion.

• If assertion is true but reason is false.

• If both assertion and reason are false.