What are the typical reactions of acids with metals?

Acids typically react with metals to produce a salt and hydrogen gas.

When an acid reacts with a metal, a type of chemical reaction called a redox reaction occurs. This is a reaction where both reduction and oxidation take place. The metal acts as a reducing agent, meaning it donates electrons to the acid, which acts as an oxidising agent by accepting these electrons. This results in the metal being oxidised to form a positive ion, and the hydrogen in the acid being reduced to form hydrogen gas.

For example, when hydrochloric acid reacts with magnesium, magnesium chloride and hydrogen gas are produced. The balanced chemical equation for this reaction is: 2HCl(aq) + Mg(s) → MgCl2(aq) + H2(g). Here, the magnesium has been oxidised (it has lost electrons) and the hydrogen in the hydrochloric acid has been reduced (it has gained electrons).

The type of salt produced in these reactions depends on the metal and the acid used. For instance, if sulphuric acid was used instead of hydrochloric acid in the above reaction, the product would be magnesium sulphate instead of magnesium chloride.

It's important to note that not all metals react with acids. Metals that are less reactive than hydrogen, such as copper, silver and gold, do not react with dilute acids. This is because these metals are unable to displace hydrogen from the acid.

In a laboratory setting, the production of hydrogen gas can be confirmed by the 'pop' test. This involves collecting the gas produced in a test tube and bringing a lit splint to the mouth of the tube. If hydrogen gas is present, it will ignite with a 'pop' sound. This is a practical and straightforward way to confirm the presence of hydrogen gas in these reactions.