Time to meet another homologous series of organic compounds, the carboxylic acids. Carboxylic acids are a family of weak acids which contain the carboxyl group (-COOH). Their general formula is CnH2n+1COOH. They are named by taking the corresponding alkane and replacing the -e on the end with -oic acid e.g.
The displayed formula for the first 4 carboxylic acids are shown below:
As before when we draw out the formula for these compounds we always draw them with the functional group shown e.g. Methanoic acid is HCOOH and never CO2H. Ethanoic acid is CH3COOH and never C2H402.
Higher tier only
Carboxylic acids with less than 6 carbon atoms are soluble in water, they dissolve to form weak acids. If you remember a weak acid forms when a solid or liquid only partly ionises when it is added to water.
similarly with ethanoic acid we have:
|carboxylic acid||molecular formula||ion formed||molecular formula of ion|
A reaction you have seen before is when hydrochloric acid reacts with a metal carbonate such as sodium carbonate or calcium carbonate:
swapping the hydrochloric acid, a strong acid for a weak carboxylic acid will produce a similar reaction but it will be much slower e.g.
The apparatus to compare the rate of reaction of a weak carboxylic acid and a strong acid with chalk (calcium carbonate) is shown below.