Which of the following are paramagnetic?
A. $\left[\mathrm{NiCl}_4\right]^{2-}$
B. $\mathrm{Ni}(\mathrm{CO})_4$
C. $\left[\mathrm{Ni}(\mathrm{CN})_4\right]^{2-}$
D. $\left[\mathrm{Ni}\left(\mathrm{H}_2 \mathrm{O}\right)_6\right]^{2+}$
E. $\mathrm{Ni}\left(\mathrm{PPh}_3\right)_4$
Choose the correct answer from the options given below :
If the half-life ( $t_{1 / 2}$ ) for a first order reaction is 1 minute, then the time required for $99.9 \%$ completion of the reaction is closest to :
Energy and radius of first Bohr orbit of $\mathrm{He}^{+}$and $\mathrm{Li}^{2+}$ are [Given $\mathrm{R}_{\mathrm{H}}=2.18 \times 10^{-18} \mathrm{~J}, \mathrm{a}_0=52.9 \mathrm{pm}$ ]
Among the given compounds I-III, the correct order of bond dissociation energy of C-H bond marked with * is :