React ethanoic acid and 1-butanol under reflux with the presence of trace amount of concentrated sulfuric acid. In this step, the amount of 1-butanol and ethanoic acid used is the same so that a maximum 70% ester yield can be synthesised at the end of the experiment. After the reactants is accommodated in the reactant flask, the trace amount of concentrated sulfuric acid is added drops-by-drops into the reactant flask and the flask is swirled while adding the acid. Additional of concentrated sulfuric acid is to use as a catalyst to increase the rate of reaction by donating a proton to the oxygen atom in carboxylic acid to allow for the mechanism for esterification and thus, the satisfactory yield of ester can be achieved. Moreover, it acts as dehydrating agent, forcing the equilibrium to the products and lead to a greater yield of ester. After the addition of trace amount of concentrated sulfuric acid, the reactant flask is heated so that the reaction can be speeded up and ester can be obtained faster. The reason of adding concentrated drops-by-drops into the reactant flask and swirl the flask while adding the acid is to prevent any part of the mixture getting too hot and reacting to form unwanted darkly coloured by-product. Before the heating of the liquid, boiling chips is added inside the reactant flask to allow a nucleation site for gradual boiling and avoid a sudden boiling surge where may cause the liquids inside the reactant flask to overflow or spill out as it has