Chemistry : The p-Block Elements

How do you prepare:

(i) K₂MnO₄ from MnO₂?

(ii) Na₂Cr₂O₇ from Na₂CrO₄?

Account for the following:

(i) Mn²⁺ is more stable than Fe²⁺ towards oxidation to +3 state.

(ii) The enthalpy of atomization is lowest for Zn in 3d series of the transition elements.

(iii) Actinoid elements show a wide range of oxidation states.

(i) Name the elements of 3d transition series that show a maximum number of oxidation states. Why does this happen?

(ii) Which transition metal of 3d series has positive E⁰ (M²⁺/M) value and why?

(iii) Out of Cr³⁺ and Mn³⁺, which is a stronger oxidising agent and why?

(iv) Name a member of the lanthanoid series that is well-known to exhibit +2 oxidation state.

(v) Complete the following equation:  MnO₄^- + 8H⁺ + 5e^- -->

What is the covalency of nitrogen in N₂O₅? 

Arrange the following in increasing order of their basic strength in aqueous solution: 

 CH₃NH₂, (CH₃)₃N, (CH₃)₂NH

What happens when 

 (i) PCl₅ is heated?

(ii) H₃PO₃ is heated?

 Write the reactions involved ?

Give reasons for the following:

(i) Bond enthalpy of F₂ is lower than that of Cl₂.

 Draw the structures of the following molecules:

(i) BrF₃

(ii) (HPO₃)₃

(iii) XeF₄ 

Account for the following:

(i) Helium is used in diving apparatus.

(ii) Fluorine does not exhibit positive oxidation state.

(iii) Oxygen shows catenation behaviour less than sulphur

Draw the structures of the following molecules:

 (i) XeF₂