Making an Ester
1.) Refluxing - React carboxylic acid with alcohol using a catalystlike concentrated sulfuric acid to speed up the reaction. Heating mixture also speeds it up, however you have to make sure the alcohol doesn't evaporate. Mixture is gently heated in a flask with a condenser which catches vapours and recycles them, giving them time to react - refluxing
2.) Distillation - Separate ester from unreacted alcohol and carboxylic acid, sulfuric acid and water. Mixture is heated below a fractionating column. When the temperature at the top of the column reaches the boiling point of the ester, the liquid that flows out of the condenser is collected - impure ester.
3.) Purification - Liquid collected - distillate, poured into tap funnel. Mixture shaken with sodium carbonate solution to remove acidic impurities. Ester doesn't mix with water, so mixture separates into two layers and lower layer of sodium carbonate solution is tapped off. The remaining upper layer is mixed with concentrated calcium chloride to remove any alcohol, which is then tapped off an removed.
4.) Drying - Any remaining water is removed by shaking it with lumps of anhydrous calcium chloride, which can absorb water - drying. The pure alcohol can be seperated from sodium chloride solution by filtration.
- Qualitative Analysis tells you what a sample contains - what substances are present
- Quantitative Analysis tells you how much it contains.
- It can be used to work out the molecular formula of a sample.
- Chemical Analysis is carried out in samples because it might be difficult to test all of the material or you may just want to test a bit so that you can use the rest for something else.
- Taking a sample also allows you to try again if something goes wrong with the test.
- A sample must represent the bulk of material being tested
- Samples are analysed in solution - aqueous means the solvent is water (aq)
- Non-aqueous means the solvent is anything other than water e.g ethanol.
- When testing chemicals, scientist follow standard procedures to carry out practical tasks.
- They follow procedures that have been agreed, they are safest, most effective and accurate.
- They can be followed within a company, nationally or internationally.