• Take two test tubes; label them as A and B. Take about 0.5 gm of sodium carbonate (Na,CO,) in test tube A and about 0.5 gm of sodium hydrogen carbonate (NaHCO,) in test tube B
• Add about 2 ml of dilute HCl to both Cork the test tubes.
• What do you observe?
• Pass the gas produced in each case through lime water (calcium hydroxide solution) as shown in Fig 2 and record your observations.

The reactions occurring in the above activities are as follows:

Na₂CO_3(s)+2HCl_(aq)→2NaCl_(aq)+H₂O₍₁₎+CO_2(g)

NaHCO_3(s)+HCl_(aq)→NaCl_(aq)+H₂O₍₁₎+CO_2(g)

Pass the gas evolved through lime water

Ca(OH)_2(aq)+CO_2(g)→CaCo₃↓+H₂O₍₁₎

On passing excess carbon dioxide the following reaction takes places:

CaCO_3(s)+H₂O₍₁₎+CO_2(g)→Ca(HCO₃)_2(aq)

Thus from above activities you can conclude that the reaction of metal carbonates and hydrogen carbonates with acids give a corresponding salt, carbon dioxide and water. We can write generalized form of these chemical reactions as shown below:

metal carbonate + acid → salt+ carbon dioxide + water

metal hydrogen carbonate + acid→ salt + carbon dioxide + water