Question

Give the conditions and the main products formed by hydrogenation of ethene. 

Answer 1

When ethene and hydrogen are passed over a finely divided catalyst such as platinum or palladium at ordinary temperature or nickel at `200°C, the two atoms of the hydrogen molecule are added to the unsaturated molecule, which thus becomes a saturated one. 

\[\ce{C2H4 + H2 ->[200°C][Ni] C2H6}\]

Answer 2

1. Temperature should be 300°C for platinum and 200°C for nickel.
2. Volumes of hydrogen and ethene gas should be equal when passed over a catalyst.
3. Heated nickel or platinum catalyst.

\[\begin{array}{cc}
\ce{H}\phantom{...}\ce{H}\phantom{........................}\ce{H}\phantom{...}\ce{H}\\
|\phantom{....}|\phantom{.........................}|\phantom{....}|\\
\ce{\underset{Product formed is ethane}{H - C = C - H + H2} ->[Ni-200^\circ C] H - C - C - H}\\
\phantom{..............................}|\phantom{....}|\\
\phantom{..............................}\ce{\underset{[Ethane]}{H\phantom{...}\ce{H}}}\\
\end{array}\]