Making Salts

When looking at making salts, it is important to remember the neutralisation reaction:

Acid + Alkali → Salt + Water

An example is with hydrochloric acid and sodium hydroxide:

Hydrochloric acid + Sodium hydroxide → Sodium chloride + Water

Here are two more examples:

Sulphuric acid + Potassium hydroxide → Potassium sulphate + Water

Nitric acid + Calcium hydroxide → Calcium nitrate + Water

Remember!

Acid Salt Ending
Hydrochloric acid Chloride
Sulphuric acid Sulphate
Nitric acid Nitrate

Another general equation for neutralisation is:

Acid + Base → Salt + Water

It is important to remember, alkalis are bases that dissolve in water.

The difference with this equation is that it takes into account the bases that do not dissolve in water, this is called an insoluble base. As insoluble bases do not dissolve in water, they will need to react as solids.

Below are some examples of this reaction:

Hydrochloric acid + Copper oxide → Copper chloride + Water

Sulphuric acid + Magnesium oxide → Magnesium sulphate + Water

Nitric acid + Calcium oxide → Calcium nitrate + Water

We will look at the second reaction to see how we can make and isolate copper chloride.

Let’s look at the equation again:

Hydrochloric acid + Copper oxide → Copper chloride + Water

And more specifically:

2HCl (aq) + CuO (s) CuCl2 (aq) + H2O (l)

Keep in mind, the ‘aq’ symbol in the equation means aqueous – dissolved in water.

Method to make copper chloride:

  1. Use a measuring cylinder to measure 30 ml of hydrochloric acid.
  2. Pour the hydrochloric acid into a boiling tube and place the tube into a beaker of hot water.
  3. Use a spatula to add copper oxide in excess and stir the solution until the hydrochloric acid has stopped reacting
  4. Use filter paper to set up a funnel and place it in a conical flask – This is so you can filter the mixture
  5. Place a gauze pad on a tripod and an evaporating dish on top of the gauze pad
  6. Once you’ve filtered the solution, pour the filtrate into the evaporating dish
  7. Set up a Bunsen burner under the tripod – To gently heat the filtrate in the evaporating dish – This will allow some of the water to evaporate
  8. Remove the evaporating dish from the heat, to somewhere warm, so that the remaining water can evaporate slowly

The copper chloride salt produced in the reaction will form crystals. Allowing the filtrate to evaporate slowly leads to larger salt crystals forming

There are other reactions you can use to make salt

Reacting Acids with Metals

Acid + Metal → Salt + Hydrogen

You can see how copper chloride is made in this reaction through the equation:

Hydrochloric acid + Copper → Copper chloride + Hydrogen

Reacting Acids with Metal Carbonates

Acid + Metal carbonate → Salt + Water + Carbon dioxide

You can see how copper chloride is made in this reaction through the equation:

Hydrochloric acid + Copper carbonate → Copper chloride + Water + Carbon dioxide