Consider the following transformation involving first order elementary reaction in each step at constant temperature as shown below.

Some details of the above reactions are listed below.

If the overall rate constant of the above transformation (k) is given as $$\mathrm{k=\frac{k_1 k_2}{k_3}}$$ and the overall activation energy $$(\mathrm{E}_{\mathrm{a}})$$ is $$400 \mathrm{~kJ} \mathrm{~mol} \mathrm{~m}^{-1}$$, then the value of $$\mathrm{Ea}_3$$ is ________ integer)

The enthalpy of formation of ethane $$(\mathrm{C}_2 \mathrm{H}_6)$$ from ethylene by addition of hydrogen where the bond-energies of $$\mathrm{C}-\mathrm{H}, \mathrm{C}-\mathrm{C}, \mathrm{C}=\mathrm{C}, \mathrm{H}-\mathrm{H}$$ are $$414 \mathrm{~kJ}, 347 \mathrm{~kJ}, 615 \mathrm{~kJ}$$ and $$435 \mathrm{~kJ}$$ respectively is $$-$$ __________ $$\mathrm{kJ}$$

$$\mathrm{Xg}$$ of ethylamine is subjected to reaction with $$\mathrm{NaNO}_2 / \mathrm{HCl}$$ followed by water; evolved dinitrogen gas which occupied $$2.24 \mathrm{~L}$$ volume at STP. X is _________ $$\times 10^{-1} \mathrm{~g}$$.

The number of the correct reaction(s) among the following is _______.