What is the role of metal or reagents written on arrows in the given chemical reactions ?
(a)
(b) `CH_(3)COOH+CH_(3)CH_(2)OHoverset("Conc.H_(2)SO_(4))toCH_(3)COOC_(2)H_(5)+H_(2)O`
(c ) `CH_(3)CH_(2)OHunderset("Heat")overset("Alk."KMnO_(4))toCH_(3)COOH`

Explanation

(a) Nickel (Ni) acts as the catalyst during the reaction. It first adsorbs the hydrogen molecule on its surface as hydrogen atoms and then alkene molecule side by side.
The two hydrogen atoms then add across the double bond of the alkene to form the addition product i.e., 2,3- dimethyl butane.
(b) Conc. `H_(2)SO_(4)` increases the rate of the forward reaction by removing `H_(2)O` formed during the reaction. In other words, conc. `H_(2)SO_(4)` acts as a dehydrating agent.
(c) Alkaline `KMnO_(4)` acts as an oxidising agent and oxidises ethanol to ethanoic acid.