Consider the following plots of rate constant versus $${1 \over T}$$ for four different reactions. Which of the following orders is correct for the activation energies of these reactions?

Kjeldahl's method cannot be used to estimate nitrogen for which of the following compounds?

The major product [B] in the following sequence of reactions is :-

Complexes (ML₅) of metals Ni and Fe have ideal square pyramidal and trigonal bipyramidal grometries, respectively. The sum of the 90°, 120° and 180° L-M-L angles in the two complexes is ________.