C2aL12  Acids and Metals

Key Words

Ammonium - a positive ion of ammonia.

Excess - too much of a substance.

Reactivity series - a comparison of the reactivity of metals.

Reagent - substance that reacts.

Salt - an ionic compound formed as a result of the reaction of a metal and a non-metal

Reduction - gaining electrons.

Grade E

Salts are made when a metal that is higher up the reactivity series than hydrogen reacts with an acid.  Hydrogen is displaced and forms hydrogen gas.

Metal + acid ® salt + hydrogen

If the metal is less reactive than the hydrogen, no reaction happens.

Salts are names according to the

• metal (e.g. potassium, nickel)

• acid (hydrochloric acid gives a chloride, nitric acid gives a nitrate, etc.)

Grade C

Here is a reaction between a metal and an acid to give a salt:

zinc + sulphuric acid ® zinc sulphate + hydrogen

Zn _(s) + H₂SO_{4 (aq)} ®  ZnSO_{4 (aq)} + H_{2 (g)}

To make the salt, we add an excess of zinc to ensure that all the acid is used up.  We then filter the zinc from the zinc sulphate.

To get the zinc sulphate crystals, we need to evaporate the water.

Grade A

Some salts are insoluble.  If we added sulphuric acid to lead, it would form a lead sulphate coat to the lead, then the reaction would stop.

At this level, you need to be able to write balanced equations for making salts from metals with acids:

magnesium + hydrochloric acid ® magnesium chloride + hydrogen

Mg _(s) + 2HCl _(aq) ®  MgCl_{2 (aq)} + H_{2 (g)}

Remember to put the state symbols in.