The spin only magnetic moment value (in Bohr magneton units) of Cr(CO)$$_6$$ is

In the following carbocation, H/CH$$_3$$ that is most likely to migrate to the positively charged carbon is :

The correct stability order of the following resonance structures is

For the reduction of NO$$_3^ - $$ ion in an aqueous solution, E$$^0$$ is + 0.96 V. Values of E$$^0$$ for some metal ions are given below:

$$\matrix{ {{V^{2 + }}(aq.) + 2{e^ - } \to V} & {{E^0} = - 1.19\,V} \cr {F{e^{3 + }}(aq.) + 3{e^ - } \to Fe} & {{E^0} = - 0.04\,V} \cr {A{u^{3 + }}(aq) + 3{e^ - } \to Au} & {{E^0} = + 1.40\,V} \cr {H{g^{2 + }}(aq) + 2{e^ - } \to Hg} & {{E^0} = + 0.86\,V} \cr } $$

The pair(s) of metals that is (are) oxidized by NO$$_3^ - $$ in aqueous solution is(are)