(N/A) Homogeneous Catalysis: When the reactants,products,and the catalyst are in the same phase,the process is said to be homogeneous catalysis.
Examples of homogeneous catalysis:
$(i)$ Oxidation of sulphur dioxide into sulphur trioxide with dioxygen in the presence of oxides of nitrogen as the catalyst in the lead chamber process:
$2 SO_{2(g)} + O_{2(g)} \xrightarrow{NO_{(g)}} 2 SO_{3(g)}$
$(ii)$ Hydrolysis of methyl acetate is catalysed by $H^+$ ions furnished by hydrochloric acid:
$CH_3COOCH_{3(l)} + H_2O_{(l)} \xrightarrow{HCl_{(l)}} CH_3COOH_{(aq)} + CH_3OH_{(aq)}$
$(iii)$ Hydrolysis of sugar is catalysed by $H^+$ ions furnished by sulphuric acid:
$C_{12}H_{22}O_{11(aq)} + H_2O_{(l)} \xrightarrow{H_2SO_{4(l)}} C_6H_{12}O_{6(aq)} + C_6H_{12}O_{6(aq)}$
Heterogeneous Catalysis: When the reactants and the catalyst are in different phases,the process is said to be heterogeneous catalysis.
Examples of heterogeneous catalysis:
$(i)$ Oxidation of sulphur dioxide into sulphur trioxide in the presence of platinum $(Pt)$ as the catalyst in the contact process:
$2 SO_{2(g)} + O_{2(g)} \xrightarrow{Pt_{(s)}} 2 SO_{3(g)}$
$(ii)$ Haber's process for the synthesis of ammonia using iron $(Fe)$ as the catalyst:
$N_{2(g)} + 3H_{2(g)} \xrightarrow{Fe_{(s)}} 2NH_{3(g)}$