Which among the following is NOT a pair of isomers?

Identify the total number of complexes having bidentate ligands in them from following list of complexes.

a) Tetracyanonickelate(II) ion

b) Trioxalatocobaltate(III) ion

c) Sodium hexafluoroaluminate(III)

d) bis(ethylenediamine)dithiocyanatoplatinum(IV)

What is the relation between the vapour pressure of solution, vapour pressure of solvent and its mole fraction in the solution?

Which of the following is obtained on oxidation of prop-1-ene with acidic $\mathrm{KMnO}_4$ ?