Chemicals in our Lives - Manufacture and Use of Chemicals

Chemicals are manufactured on both a large and small scale. The ways in which some chemicals are made has altered over the years due to increased demand and awareness of environmental concerns.

Alkalis

An alkali is a compound that dissolves to give a solution with a pH higher than 7.

Before industrialisation in the 1700s, alkalis were still needed for a number of uses:

• Converting oils and fats into soap
• Making glass
• Neutralising acidic soils
• Making chemicals that bind natural dyes to cloth.

Traditional sources of alkalis to enable these processes included burnt wood (potash) and stale urine (ammonia). Alkalis contain an important property that allows them to neutralise acids. When this happens a salt is made.

acid + alkali → salt + water

Reactions of Alkalis

Common examples of alkalis include soluble hydroxides and carbonates. When each of these alkalis reacts with an acid, there is a difference in the products that are formed.

When an alkaline hydroxide reacts with an acid, salt and water are formed. This is shown by the general equation:

Alkaline hydroxide + acid → salt + water

For example

Sodium hydroxide + hydrochloric acid → sodium chloride + water

When an alkaline carbonate reacts with an acid, salt and water are again formed but there is also a third product, carbon dioxide.

Alkaline carbonate + acid → salt + water + carbon dioxide

For example

Calcium carbonate + sulfuric acid → calcium sulfate + water + carbon dioxide

Note how the name of the salt is found - the first part of the name comes from the metal in the alkali used, the second comes from the acid used.

Making Alkalis

Due to increased industrialisation in the 1700s there was a shortage of alkali. This led to the need for manufacture on a large scale.

The LeBlanc Process

This was a process invented to make alkali sodium carbonate on a large scale. Sodium chloride was mixed with sulfuric acid before…