In which of the following pairs of molecules/ions both the species are not likely to exist?

Consider the following liquid-vapour equilibrium

Liquid $\rightleftharpoons$ Vapour

Which of the following relations is correct ?

If uranium (mass number 238 and atomic number 92) emits an a-particle, the product has mass number and atomic number.

Which of the following arrangements does not represent the correct order of the property stated against it?

Which of the following does not show optical isomerism? (en = ethylenediamine)

Select correct matching.

Which among the following statements are true for the complex $[Co(NH_3)_6][Cr(CN)_6]$?
(i) It is a non-electrolyte
(ii) The magnitude of the charge on each complex ion is three
(iii) The complex will not conduct current in aqueous solution
(iv) The complex will exhibit co-ordination isomerism
(v) The magnitude of the charge on each complex ion is one

The pair of species with the same bond order is

Consider the following compounds:

The root mean square velocity of an ideal gas at constant pressure varies with density (d) as