Activity 2.5 Class 10 Science

This activity explains the reaction of sodium carbonate and sodium hydrogen carbonate with acids, taken from chapter 2, Acids, Bases, and Salts.

How do Metal Carbonates and Metal Hydrogen Carbonates React with Acids?

Aim of the activity

To observe the reaction of carbonates and bicarbonates with acid

Material used

   1. Sodium carbonate

   2. Sodium hydrogen carbonate   

   3. Dilute hydrochloric acid

   4. Lime water

   5. Test tubes

   6. Dropper

   7. Delivery tube

   8. Cork

   9. Test tube stand

Procedure

We take two test tubes and label them as A and B. Now we take  about 0.5 g of sodium carbonate (`Na_2CO_3`) in test A and about 0.5 g of sodium hydrogen carbonate (`NaHCO_3`) in test tube B.

 After that, we add about 2 mL of dilute `HCl` to both the test tubes and observe the changes.

Now we pass the gas produced in each case through lime water (calcium hydroxide solution)

Observation

Test tube	Substance used	After adding `HCl`	Effect on lime water
A	`Na_2CO_3`	Vigorous effervescence	Lime water turns milky
B	`NaHCO_3`	less Vigorous effervescence	Lime water turns milky

Explanation

    1.  Carbon dioxide gas is produced in both reactions.

    `NaCO_3 + 2HCl → 2NaCl + H_2O + CO_2`

     `NaHCO_3 + HCl → NaCl + H_2O + CO_2`

 

   2. When `CO_2` is passed through lime water, an insoluble substance, calcium carbonate, is formed, so the solution turns milky.

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

When the gas is passed in excess, calcium hydrogen carbonate is formed and turns milky.

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

Conclusion

All acids react with metal carbonates and metal hydrogen carbonates to  form  water and the corresponding salt and `CO_2` gas

Frequently Asked Questions

   1. Why does lime water turn milky in this activity?

Answer – `CO_2` reacts with lime water to form an insoluble calcium carbonate, so the solution appears milky.

   2. In which test tube more vigorous reaction take place?

Answer – The test tube A shows the vigorous reaction because sodium carbonate reacts vigorously with `HCl`.

   3. What is the chemical formula of lime water?

Answer – `Ca(OH)_2`