Neet PYQ 2007

The product formed in aldol condensation is:

If $\text{NaCl}$ is doped with $10^{-4}\text{ mol\%}$ of ${\text{SrCl}}_2$, the concentration of cation vacancies will be ($N_A=6.02\times 10^{23}{\text{ mol}}^{-1}$):

The $d$ -electron configurations of ${\text{Cr}}^{2+}$, ${\text{Mn}}^{2+}$, ${\text{Fe}}^{2+}$ and ${\text{Ni}}^{2+}$ are $3d^4$, $3d^5$, $3d^6$ and $3d^8$ respectively. Which one of the following aqua complexes will exhibit the minimum paramagnetic behaviour?

The order of decreasing reactivity towards an electrophilic reagent for the following: (i) Benzene, (ii) Toluene, (iii) Chlorobenzene, and (iv) Phenol would be:

In which of the following pairs, the two species are isostructural?