Reaction of HCl With Metal Carbonate

Reaction of Acids With Metal Carbonates

HCl is a strong acid that completely dissociates in water to form H⁺and Cl^– ions. Na₂CO₃ is a basic salt because it is formed by the reaction of a strong base like NaOH and a weak acid like carbonic acid (H₂CO₃).

When dil. HCl reacts with any metal carbonate like sodium carbonate or sodium bicarbonate, a brisk effervescence of CO₂gas appears.

2HCl (aq) + Na₂CO₃ (s) → 2NaCl (aq) + H₂O (l) + CO₂ (g)

When the carbon dioxide gas produced during the reaction is passed through limewater, it turns milky white due to the precipitation of white calcium carbonate.

CO₂(g) + Ca(OH)₂(aq) → CaCO₃(s) + H₂O(l)

However, on passing excess carbon dioxide the milky colour of the solution fades away due to the formation of water-soluble calcium bicarbonate.

CaCO₃(s) + H₂O(l) + CO₂(g) → Ca(HCO₃)₂(aq)

To perform this experiment, apparatus and chemicals are required: Test tubes, Beaker

Watch glass, Spatula, Thistle funnel, Delivery tube, Double bored cork, Hydrochloric acid, Sodium carbonate and Limewater

Experiment Procedure

To understand the Reaction of HCl with Metal Carbonate, we have to follow the given procedure.

Take about 1 g of sodium carbonate in a clean and dry test tube.
Add about 2 mL of dil. hydrochloric acid to it.
Effervescence will start coming from the reaction mixture.
Fix a delivery tube through a cork to the mouth of the test tube and pass the liberated gas through the freshly prepared lime water. Observe what happens. Do you see bubbles of it in the lime water? Does it turn milky? If yes, it shows the presence of carbon dioxide.

Precautions

While performing this experiment, we have to follow these precautions

Handle hydrochloric acid and sodium carbonate very carefully.
Shake the solutions and reaction mixtures carefully without spillage.
Wear a lab coat before entering the chemistry lab.

Q1. How do acids react with metal carbonates?

Answer: An acid reacts with a metal carbonate, such as Na2CO3, to produce salt, water and carbon dioxide gas.

2HCl(aq) + Na2CO3(aq) → 2NaCl(aq) + H2O(l) + CO2(g)

Q2. What happens when hydrochloric acid reacts with magnesium carbonate?

Answer: When hydrochloric acid reacts with magnesium carbonate, magnesium chloride, water and carbon dioxide are formed. The chemical reaction is given below:

2HCl(aq) + MgCO3(aq) → MgCl2(aq) + H2O(l) + CO2(g)

Q3. How do we test carbon dioxide gas formed due to the reaction of metal carbonate with acids?

Answer: When the carbon dioxide gas produced during the reaction is passed through limewater, it turns milky white due to the precipitation of white calcium carbonate.

CO2(g) + Ca(OH)2(aq) → CaCO3(s) + H2O(l)

Q4. Why does the milky colour of calcium carbonate disappear on passing excess carbon dioxide through it?

Answer: However, on passing excess carbon dioxide, the milky colour of the solution fades away due to the formation of water-soluble calcium bicarbonate.

CaCO3(s) + H2O(l) + CO2(g) → Ca(HCO3)2(aq)

Q5. Why do we observe bubbles when HCl is added to a metal carbonate?

Answer: The bubbles observed when HCl is added to a metal carbonate are due to the formation of carbon dioxide gas. The gas escapes as bubbles during the reaction.