GCSE Chemistry – Acids and Alkalis

Making salts

Salts could be prepared from the reactions of acids. Here are few methods summarised.

From metal and acid

We can make salts by reacting acids with metals

This only works if the metal is above hydrogen in the reactivity series

When the acid reacts with a more reactive metal, hydrogen gas is produced along with a salt.

From acid and bases

When we react an acid with a base we produce a solution which consists of a salt and water. This type of salt is soluble. When an acid reacts with an alkali neutralisation takes place During neutralisation H+ ions react with OHions to form water When we react acids and alkalis we need to know they’ve completely reacted – indicator paper, pH probe Metal + Acid → Salt + Hydrogen

We can sometimes make salts by combining two solutions. This makes an insoluble salt, which is called a precipitation reaction because the insoluble solid is called a precipitate. Silver nitrate and sodium chloride are both soluble. When you mix their solutions together, you make soluble sodium nitrate and insoluble silver chloride: The silver chloride appears as tiny particles suspended in the reaction mixture – it forms a precipitate. The precipitate can be filtered, washed with water on the filter paper, and then dried in an oven. silver nitrate + sodium chloride → sodium nitrate + silver chloride AgNO3(aq) + NaCl(aq) → NaNO3(aq) + AgCl(s)

Method for acid + insoluble base

  1. We find solutions which contain the two halves of the salt.
  2. These solutions are mixed and form a precipitate, which can then be filtered off.
  3. The precipitate is washed and dried e.g. to make silver chloride, we mix solutions of silver nitrate and sodium chloride.