$($a$)$ Provide five characteristics of a catalyst.

$($b$)$ Distinguish between homogeneous calalysis and heterogeneous catalysis with the aid of one example for each

$(4)$

$($c$)$ Outline the main steps taking place during the catalytic hydrogenation of $1.$ propene on the surface of a nickel catalyst.

$($d$)$ Define the following terms:

i$.$ Adsorption

ii$.$ Desorption

iii. Adsorptive

iv$.$ Adsorbate

v$.$ Adsorbent

$($e$)$ Provide two characteristic differences betwoen chemisorption and physisorption processes.

$(4)$

$($f$)$ Derive the expression for the Langmuir adsorption isotherm.

$(5)$