13.2 Acid-base reaction (ESBQY)

The reaction between an acid and a basic is well-known as a neutralisation reaction. Frequently when one acid and base reaction a salt and water will certainly be formed. We will certainly look at a couple of examples the acid-base reactions.

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In chemistry the word salt walk not mean the white substance the you sprinkle on her food (this white substance is a salt, however not the just salt). A salt (to chemists) is a product of one acid-base reaction and also is made up of the cation from the base and the anion native the acid.

Hydrochloric acid reacts with sodium hydroxide to form sodium chloride (a salt) and water. Salt chloride is consisted of of \\(\\textNa^+\\) cations from the basic \\((\\textNaOH)\\) and \\(\\textCl^-\\) anions from the mountain \\((\\textHCl)\\).

\\<\\textHCl (aq) + \\textNaOH (aq) \\rightarrow \\textH_2\\textO (l) + \\textNaCl (aq)\\>

Hydrogen bromide reacts through potassium hydroxide to type potassium bromide (a salt) and water. Potassium bromide is consisted of of \\(\\textK^+\\) cations native the base \\((\\textKOH)\\) and also \\(\\textBr^-\\) anions from the mountain \\((\\textHBr)\\).

\\<\\textHBr (aq) + \\textKOH (aq) \\rightarrow \\textH_2\\textO (l) + \\textKBr (aq)\\>

Hydrochloric acid reacts with ammonia to kind ammonium chloride (a salt). Ammonium chloride is made up of \\(\\textNH_4^+\\) cations from the basic \\((\\textNH_3)\\) and also \\(\\textCl^-\\) anions indigenous the mountain \\((\\textHCl)\\).

\\<\\textHCl (aq) + \\textNH_3\\text(aq) \\rightarrow \\textNH_4\\textCl (aq)\\>

You should notification that in the very first two examples, the base consisted of \\(\\textOH^-\\) ions, and also therefore the commodities were a salt and water. \\(\\textNaCl\\) (table salt) and \\(\\textKBr\\) room both salts. In the 3rd example, \\(\\textNH_3\\) additionally acts together a base, regardless of not having actually \\(\\textOH^-\\) ions. A salt is still developed as the only product, but no water is produced.

It is essential to realise how valuable these neutralisation reactions are. Below are part examples:

Domestic uses

Calcium oxide (\\(\\textCaO\\)) is a base (all metal oxides space bases) that is placed on soil that is too acidic. Powdered limestone \\((\\textCaCO_3)\\) can additionally be used but its action is much slower and also less effective. These substances can also be provided on a bigger scale in farming and in rivers.

Limestone (white rock or calcium carbonate) is offered in pit latrines (or long drops). The limestone is a base that helps come neutralise the acidic waste.

Biological uses

Acids in the stomach (e.g. Hydrochloric acid) play critical role in helping to digest food. However, as soon as a person has actually a stomach ulcer, or when there is too lot acid in the stomach, this acids can reason a the majority of pain. Antacids room taken to neutralise the mountain so that they don\"t burn as much. Antacids room bases i m sorry neutralise the acid. Instances of antacids are aluminium hydroxide, magnesium hydroxide (“milk the magnesia”) and sodium bicarbonate (“bicarbonate of soda”). Antacids can likewise be offered to relax heartburn.

Industrial uses

Basic calcium hydroxide (limewater) can be provided to absorb harmful acidic \\(\\textSO_2\\) gas that is released from power stations and from the burn of fossil fuels.

Bee stings space acidic and also have a pH in between \\(\\text5\\) and also \\(\\text5,5\\). They have the right to be soothed by making use of substances such together bicarbonate that soda and also milk of magnesia. Both bases assist to neutralise the acidic punishment sting and also relieve some of the itchiness!

Acid-base reactions


To investigate acid-base reactions.

Apparatus and materials

Volumetric flask conical flasks sodium hydroxide systems hydrochloric acid equipment pipette indicator



Use the pipette to add \\(\\text20\\) \\(\\textml\\) that the sodium hydroxide equipment to a volumetric flask. Fill as much as the note with water and shake well.


Measure \\(\\text20\\) \\(\\textml\\) the the salt hydroxide solution into a conical flask. Include a few drops that indicator.

Slowly add \\(\\text10\\) \\(\\textml\\) that hydrochloric acid. If over there is a colour adjust stop. If not include another \\(\\text5\\) \\(\\textml\\). Continue adding \\(\\text5\\) \\(\\textml\\) increments till you notification a colour change.


The solution transforms colour after a collection amount that hydrochloric mountain is added.

In the over experiment you used an indicator come see as soon as the acid had neutralised the base. Indications are chemical compounds that readjust colour relying on whether they are in an mountain or in a base.

A encourage experiment because that informal assessment on discovering organic indicators is included. Learners have the right to test a range of colourful plants to see what happens to each plant when blended with an mountain or a base. The basic idea is for learners come extract the colour of the plant by cook the tree matter and also then draining the liquid. Because that substances such together the curry powder, learners can dissolve this in water and also for the tea they have the right to brew a cup the tea and then remove the teabag prior to testing. The result liquid deserve to then be tested to watch if the is one indicator. An alternative to mixing the acid or base right into the liquid is to soak strips of document in the liquid and also then ar a drop of the mountain or basic onto the paper. The experiment below additionally covers some various other substances such together baking powder, vanilla essence and onions. Baking flour fizzes in acids however not in bases. Onions and also vanilla essence lose their characteristic smell when in a straightforward solution.

It is crucial that learners carry out not location their encounters or noses directly over or right into the beaker as soon as smelling the onions and vanilla essence. Lock must organize the maker in one hand and use the various other hand to waft (i.e. Wave their hand ago and forth) the smell towards their face.

Acids and also bases space corrosive and also can reason serious burns so need to be handled with care.



To recognize which plants and foods can act as indicators.

Apparatus and materials

feasible indicators: Red cabbage, beetroot, berries (e.g. Mulberries), curry powder, red grapes, onions, tea (rooibos or regular), baking powder, vanilla essence acids (e.g. Vinegar, hydrochloric acid), bases (e.g. Ammonia (in countless household cleaners)) to check Beakers


Take a small amount of your an initial possible indicator (do not usage the onions, vanilla essence and also baking powder). Boil the problem up until the water has changed colour.

Filter the resulting solution right into a beaker being careful not to get any plant matter right into the beaker. (You can also pour the water with a colander or sieve.)

Pour half the resulting coloured solution right into a 2nd beaker.

Place one beaker onto an A4 sheet of file labelled “acids”. Ar the various other beaker top top a paper of file labelled “bases”.

Repeat v all your other possible indicators (except the onions, vanilla essence and baking powder).

Into all the beakers top top the acid sheet closely pour \\(\\text5\\) \\(\\textml\\) that acid. Document your observations.

Into all the beakers ~ above the base sheet very closely pour \\(\\text5\\) \\(\\textml\\) of base. Document your observations.

If friend have more than one mountain or base climate you will have to repeat the over steps to acquire fresh indicator samples because that your second acid or base. Or you have the right to use much less of the result coloured systems for each acid and also base you want to test.

Observe the smell of the onions and also vanilla essence. Location a small piece the onion right into a beaker. This is for trial and error with the acid. Pour \\(\\text5\\) \\(\\textml\\) of acid. Tide your hand over the height of the beaker to punch the air towards your nose. What execute you an alert about the odor of the onions? Repeat through the vanilla essence.

Place a small piece the onion right into a beaker. This is for trial and error with the base. To water \\(\\text5\\) \\(\\textml\\) that base. Wave your hand over the top of the manufacturer to punch the air in the direction of your nose. What do you notice about the odor of the onions? Repeat through the vanilla essence.

Finally ar a teaspoon of baking powder right into a beaker. Closely pour \\(\\text5\\) \\(\\textml\\) the acid into the beaker. Record your observations. Repeat utilizing the base.

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Curry powder


Red grapes


Vanilla essence

Baking powder



Results through acid

Results v base

Red cabbage

You have to note that few of the substances readjust colour in the visibility of either an acid or a base. The baking powder fizzes once it is in the acid solution, yet no reaction is provided when the is in the basic solution. Vanilla essence and onions should shed their characteristics smell as soon as in the base.