Higher and foundation tier

Neutralisation Reactions

It is very easy and straight forward to carry out a neutralisation reaction by mixing an acid and an alkali together. The basic method is shown in the illustration below. Three conical flasks are needed, one contains an acid, one contains an alkali and the one in the middle can contain either an acid or an alkali. Universal indicator or some other suitable indicator is needed to enable you to decide when the acid and alkali have neutralised each other. Remember that universal indicator is red in a strong acid, violet in a strong alkali and green when neutral. So you simply add acid or alkali to the middle beaker. If you add alkali to the middle beaker then slowly, drop by drop with continual stirring add the acid until the indicator turns green. If you add too much acid the simply add a little alkali to neutralise it. Keep mixing until the indicator turns green .

The method is shown in the image below:  neutralisation reaction

Once you have neutralised the alkali (sodium hydroxide) with the acid (hydrochloric) you will be left with the salt (sodium chloride) you have made which will be dissolved in water. To get the solid salt you could simply place it in an evaporating basin and boil to evaporate the water. Unfortunately, the salt will be covered in the indicator! But luckily there is a solution. Powdered charcoal is excellent at removing odours, tastes and smells from substances. It is used for example in kitchen extractor hoods and gas masks for this very reason. So simply add a few spatulas of powered charcoal to your mixture and stir for a few minutes. Then filter to remove the charcoal and finally evaporate the water to leave the solid salt. The method is outlined below:

 neutralisation reaction method

Key Points

Practice questions

Check your understanding - neutralisation reaction questions