NIOS Class 10 Science and Technology Activity 8.3 Acids, Bases and Salts

This activity explains the reaction of acids with metal carbonates and metal hydrogen carbonates.

 

NIOS Class 10 Science and Technology Project File

This activity is based on the NIOS Class 10 Science and Technology chapter 8: Acids, Bases, and Salts.

Aim of the activity

To study the chemical reaction of dilute hydrochloric acid with sodium carbonate and sodium hydrogen carbonate.

Materials Required

   1. Sodium carbonate

   2. Sodium hydrogen carbonate

   3. Dilute hydrochloric acid

   4. Lime water

   5. Boiling tube

   6. Cork

   7. Thistle funnel

   8. Delivery tube

   9. Test tube

  10.Test tube stand

Procedure

We take a  clean, boiling tube and add about 0.5g of sodium carbonate to it, and fix this tube to a stand. Now we seal the boiling tube with a crock fitted with a thistle funnel and delivery tube.

 

 We add 3 mL of dilute hydrochloric acid through a thistle funnel  

Now we the other end of the delivery tube is dipped in the lime water and observe the changes.

 We also repeat the same activity with sodium hydrogen carbonate.

Observation

When dilute HCl is added to sodium carbonate or sodium hydrogen carbonate, we can see effervescence, and a gas is evolved.

 When this gas is passed through lime water, it turns milky. When excess CO₂ gas is passed through the milky solution, it turns clear again.

Explanation

Acid reacts with metal carbonate or metal hydrogen carbonate to produce carbon dioxide gas, water, and salt.

Na₂CO₃   + 2HCl → 2NaCl + H₂O +  CO₂↑

NaHCO₃ +HCl → NaCl + H₂O +  CO₂↑

Carbon dioxide gas turns lime water milky  because an insoluble calcium carbonate is formed.

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

When excess CO₂ is passed in the milky solution, it turns clear due to the formation of soluble calcium hydrogen carbonate.

 CaCO₃   +H₂O   + CO_2(g) →Ca(HCO₃)_2(aq)

Conclusion

We can conclude through this activity that metal carbonate or metal hydrogen carbonate reacts with acid to produce carbon dioxide gas. This activity is a classic test for CO₂ gas.

Frequently Asked Questions

   1. How do we know CO₂ is formed in this activity?

Answer – Because the evolving gas turns lime water milky.

   2. Why does lime water turn milky on passing carbon dioxide gas?

Answer – Because an insoluble substance, calcium carbonate, is formed.

   3. Why milky solution become clear when excess CO₂ gas is passed?

Answer- When excess carbon dioxide is passed through a milky solution, calcium carbonate gets converted into calcium hydrogen carbonate, which is soluble.

   4. What is the formula of calcium hydrogen carbonate?

Answer – Ca(HCO₃)₂