Reaction of acids with metal carbonate

These notes are based on the chapter Acids Bases and Salts from NCERT book based on CBSE syllabus.

What happens when an acid reacts with metal carbonate? Acids give carbon dioxide gas and respective salts along with water when they react with metal carbonates.

Metal carbonate + Acid ⇨ Salt + Carbon dioxide + Water

Example 1

Hydrochloric acid gives carbon dioxide gas, sodium chloride along with water when it reacts with sodium carbonate.

Na₂CO₃ + 2HCl ⇨ 2NaCl + CO₂ + H₂O

Example 2

Hydrochloric acid gives carbon dioxide, magnesium chloride and water when it reacts with magnesium carbonate.

MgCO₃ + 2HCl ⇨ MgCl₂ + CO₂ + H₂O

Example 3

Hydrochloric acid gives carbon dioxide gas, calcium chloride and water when it reacts with calcium carbonate.

CaCO₃ + 2HCl ⇨ CaCl₂ + CO₂ + H₂O

Example 4

Sulphuric acid gives calcium sulphate, carbon dioxide gas, calcium sulphate and water when it reacts with calcium carbonate.

CaCO₃ + H₂SO₄ ⇨ CaSO₄ + CO₂ + H₂O

Example 5

Sulphuric acid gives sodium sulphate, carbon dioxide gas and water when it reacts with sodium carbonate.

Na₂CO₃ + H₂SO₄ ⇨ Na₂SO₄ + CO₂ + H₂O

Example 6

Nitric acid gives sodium nitrate, water and carbon dioxide gas when it reacts with sodium carbonate.

2HNO₃ + Na₂CO₃ ⇨ NaNO₃ + 2H₂O + CO₂

Reaction of acid with hydrogen carbonates (bicarbonates)

It is important to remember that hydrogen carbonate is also called bicarbonate.

What happens when an acid reacts with metal bicarbonate? Acids give carbon dioxide gas, respective salt and water when they react with metal hydrogen carbonate.

Acid + Metal hydrogen carbonate ⇨ Salt + Carbon dioxide + Water

Example 1

Hydrochloric acid gives carbon dioxide, sodium chloride and water when it reacts with sodium bicarbonate.

NaHCO₃ + HCl ⇨ NaCl + CO₂ + H₂O

Example 2

Sulphuric acid gives sodium sulphate, carbon dioxide gas and water when it reacts with sodium bicarbonate.

2NaHCO₃ + H₂SO₄ ⇨ Na₂SO₄ + 2CO₂ + 2H₂O

Sodium bicarbonate is also known as sodium hydrogen carbonate, baking soda, baking powder, bread soda and bicarbonate of soda.

Test for evolution of carbon dioxide gas: Carbon dioxide turns lime water milky when passed through it. This is the characteristic test for carbon dioxide gas.

The gas evolved because of reaction of acid with metal carbonate or metal hydrogen carbonate turns lime water milky. This shows that the gas is carbon dioxide gas. This happens because of formation of white precipitate of calcium carbonate.

Ca(OH)₂ + CO₂ ⇨ CaCO₃ + H₂O

CaCO₃ + CO₂ + H₂O ⇨ Ca(HCO₃ )₂

But when excess of carbon dioxide is passed through lime water, it makes milky colour of lime water disappear. This happens because of formation of calcium hydrogen carbonate. As calcium hydrogen carbonate is soluble in water, thus the milky colour of solution mixture disappears.

Reaction of acid with marble and egg shell: Since, marble and egg shell are made of calcium carbonate, hence when acid is poured over marble or egg shell, bubbles of carbon dioxide are formed.

Historical Monuments and Acid Rain:

How is acid rain formed?

Burning of fossil fuels releases oxides of sulphur and nitrogen. Nitrogen oxide and sulphur dioxide form nitric acid and sulphuric acid on reaction with water. When rain droplets mix with these gases (present in atmosphere because of pollution) they form acid rain.

Effect of acid rain

Acid rain causes damage to historical monuments and other buildings. For example, the Taj Mahal, which is made of marble, is getting damaged because of reaction with acid rain. Marble is calcium carbonate which reacts with the acid and thus gets corroded.

Acid & Base and Fire Extinguisher

How does soda acid fire extinguisher work?

Metal carbonate or metal hydrogen carbonate and acid are used in fire extinguisher to produce carbon dioxide gas. Acid and metal carbonate or bicarbonate are kept in separate chambers in a fire extinguisher. On emergency they are allowed to react with one another. The carbon dioxide gas so produced is poured over fire. As carbon dioxide does not support burning, it puts off the fire.