[Music] hi and welcome back to free science lessons. co.uk by the end of this video you should be able to describe the structures of the first four carboxilic acids you should then be able to describe what happens when carboxilic acids dissolve in water and finally you should be able to describe the reactions of carboxilic acids with metal carbonates and with an alcohol and remember that this material is for triple chemistry students only in the last couple of videos we've looked at alcohols I'm shown you the displayed formula for the first four alcohols here we saw that if we react an alcohol with an oxidizing agent we produce a carboxilic acid so here I'm showing you the displayed formula of the first four carboxilic acids the carboxilic acids are a homologous Series in other words they all have the same functional group and I'm showing you the carboxilic acid function group in green here now rather than drawing all of the individual atoms and bonds scientists often use a structural formula instead so here I'm showing you the structural formulas of the carboxilic acids in the exam you could be shown the displayed or the structural formula for a carboxilic acid and as to identify it so it's important that you learn these okay we're going to look now what happens when we dissolve carboxilic acids in water in water carboxilic acids are weak acids I'm showing you ethanolic acid in aquous solution here in this case ethanolic acid is ionizing to produce the ethanoate ion and H+ as you can see this is a reversible reaction that means that the ethanoate ion and the H+ can recombine to form ethanolic acid because carboxilic acids only partially ionized in aquous solution they are weak acids that means that carboxilic acid acids have a higher pH than strong acids such as hydrochloric acid okay we're going to look now at two key reactions of carboxilic acids the first is with metal carbonates this shows ethanolic acid reacting with sodium carbonate as you can see we've made the salt sodium ethanoate and carbon dioxide gas we've also made water now all of the carboxilic acids react like this with metal carbonates I'm showing you here the reaction between propanoic acid and potassium carbonate and again we've made carbon dioxide and water and in this case we've made the salt potassium propanoate okay the second key reaction of carboxilic acids is with alcohols when we react a carboxilic acid with an alcohol we make a molecule called an Esther we also make water Esters are really useful molecules as they often have a pleasant smell so they're used a lot in Foods I'm showing you here the reaction between ethanolic acid and the alcohol ethanol we've made the Esther ethy ethanoate and you could be asked to name this Esther in your exam now there are a couple of key points about this reaction firstly this reaction requires sulfuric acid as a catalyst and again you could be asked that in your exam secondly this is a reversible reaction so you might see this reaction in a question on reversible reactions remember you'll find plenty of questions on carboxilic acids in my vision workbook and you can get that by clicking on the link above [Music]