• Question: Why do acids and alkalis react when mixed?

    Asked by Ioan cruyf to Jayne on 10 Nov 2017.
    • Photo: Jayne Ede

      Jayne Ede answered on 10 Nov 2017:

      Yes they do. Mixing acids and alkalis (alkalis are also called ‘bases’) is quite a common thing in chemistry, and when you mix an acid with an alkali you get a salt.

      So for example – table salt (sodium chloride, NaCl) could be made by mixing hydrochloric acid mixed with water (HCl(aq)) with sodium hydroxide (a base – NaOH). The equation would look like this:

      HCl(aq) + NaOH -> NaCl + H2O(which we know is water)

Comments

  • Photo: Jayne

    Jayne commented on :

    Ah dude I’ve just seen that you asked WHY they react, so I’ll continue! They react because certain atoms, based on their charge and size, prefer to be with certain other atoms. This is especially true if they can steal each others electrons. Sodium has one spare electron that it is desperate to get rid of to become stable, whereas chlorine is missing one – so they become a salt (NaCl) which is a really strong bond. In the situation above, water is also really really stable molecule and so the acid and the base rearrange themselves really quickly to form water too.

    If you’re interested in this, something to look up is the difference between ‘ionic’ and ‘covalent’ bonds.

    Ionic bonds, like in salts where the electron is taken from one atom and given to another – is like magnetising the two atoms making them stick together really strongly

    ‘Covalent’ bonds like in the oxygen molecule O2, is where the electrons are shared and the bond is weaker.

  • Photo: mithu2017

    mithu2017 commented on :

    That is a little bit complex for me to understand 🙁

    • Photo: Jayne

      Jayne commented on :

      Then I must do better! Sorry for being over-complicated!

      So in acid and alkali reactions, you have chemicals made of two or more atoms which are stuck together by a chemical bond. However, they want to be attached to some atoms more than others. Which means if you put an acid and an alkali together, they do their best to detach from the atoms they’re attached to, and make a new bond with a different atom which they prefer. The example I used above, with HCl (the acid) and NaOH (the alkali) works because Na and Cl really really want to make bonds with each other more than any other atoms, so they kick off any other atoms in order to stick together, and that ends up being NaCl – table salt that you put on your chips!

      I hope that makes more sense this time?