Property 3: The reaction of metals with acid
Acids react with many compounds easily.
Metals react with acids to give salt and hydrogen gas.
Metal + Dilute Acid → Salt + Hydrogen
- Reaction with Hydrochloric acid:
- Potassium and sodium react very vigorously with hydrochloric acid. It is an explosive reation.
- Magnesium reacts with hydrochloric acid to form magnesium chloride along with the release of hydrogen gas with the formation of bubbles.
𝑴𝒈 + 𝟐𝑯𝑪𝒍 → 𝑴𝒈𝑪𝒍𝟐 + 𝑯𝟐
- The reactions are similar for aluminium, zinc and iron. All give out their chlorides with hydrogen gas. But the rate of formation of bubbles is diifferent.
Rate of Formation of Bubbles:
Mg > Al > Zn > Fe
- Metal copper doesn’t react with Hydrochloric acid at
- Reaction with Nitric acid:
Hydrogen gas is not released when a metal reacts with nitric acid. It’s because nitric acid is a very strong oxidising agent, which means that the nitric acid oxidises the hydrogen to form water. And the acid gets reduced to any of the nitrogen oxides (𝑁2𝑂, 𝑁𝑂, 𝑜𝑟 𝑁𝑂2).
Metals like gold do not react with individual acids. Hydrochloric acid cannot dissolve gold and neither can nitric acid.
There is a mixture of acids called aqua-regia that can dissolve gold. Aqua-regia is a mixture of concentrated hydrochloric acid and concentrated nitric acid in ratio three to one. It’s a very corrosive liquid, one of the very few that can dissolve gold.
Summary
| The reaction of metals with acids | Metal + Dilute Acid → Salt + Hydrogen |
| Aqua-regia | A mixture of concentrated hydrochloric acid and concentrated nitric acid in ratio three to one |