Etherification using carboxylic acid and alcohol requires an acid catalyst. In an experiment the acid form of an ion-exchange resin is used. This resin, in the form of small beads, is a cross-linked polystyrene that bears sulfuric acid groups on some of the phenyl groups. Basically it is an immobilized form of p-toluenesulfonic acid, an organic-substituted sulfuricacid. Explain what advantage does this catalyst have over using concentrated sulfuric acid?