ACIDS

Now ladies and gentlemen, things are going to get very Factual so get your notepads out and shift your brains in gear for its time to memorise some definitions.

Oh and here's a very awesome cat I found.



As I'm sure you're all aware each acid contains a H+ ion. Sounds familiar?? I hope so. Then what an acid is should also click into place: Acid is a proton donor. Which just means that in a reaction the acid will give up its H+ ion to swap it for something else. And what is a H+ ion, well it's just a proton all by itself.

You are also expected to name some common acids and know their formulae. So I've made this easy for you and listed them here:

Hydrochloric acid: HCl
Sulphuric acid: H2SO4
Nitric acid: HNO3

The opposite, or the counterpart of you will, of an acid is a base. And also have to know some bases:

Metal oxides: MgO
Metal hydroxides: Mg(OH)2
Ammonia: NH3

These, I'll tell you straight away, can be used to neutralise acidic soil because when you add acid to base in the right amounts you produce water or a neutral solution and salt.

An Alkali is a soluble base that releases OH- ions in an aqueous solutions. So whereas an acid releases (donates) a H+ ion and alkali donates a OH- ion.

When an acid and alkali react together in the correct amount a neutral solution is formed, like I mentioned above. However a salt is always formed. A SALT is produced when the H+ ion is replaced by a metal ion or NH3.

You need to also be able to explain that a base accepts H+ ions from an acid (like I said a couple of times). For example:

• OH- and H+ ions give H2O
• NH3 and H+ give NH4+ ion.

There is also another part to acids that you may hate, or love depending on your view point of Chemistry and maths in general. It is water of crystallisation. When a crystal forms (salt) there is bound to be some water molecules locked up in there this a hydrated salt. An Anhydrous salt is a salt without water.

To work out the water of crystallisation you need to:

1. Work out mass of the hydrous and anhydrous ( or you may be given them).
2. Take them away from each other. This will give you the mass of the water.
3. Now work out the moles of water and the anhydrous salt (using the triangles that you have learned).
4. Once you have the moles divide both values by the smallest one, this will give you the ratio of anhydrous salt to water.
5. Ta dah! You have worked out the water of crystallisation. The value of the ratio for water is the answer. Stick that in front of the water and BOOM!
6. Make sure you have a DOT "." before the H2O to ensure that this is a water of crystallisation and not some crazy molecule you just came up with.