Reaction with Metal Carbonates and Bicarbonates - UNSOLVED PRACTICE SET

Q7. Write balanced chemical equations for the reaction of dilute hydrochloric acid with: (i) Sodium carbonate, (ii) Sodium bicarbonate, (iii) Calcium carbonate.

Q8. How can you test for the presence of carbonate ions (CO₃²⁻) in a given salt? Describe the test with observations.

Q9. Your mother uses baking soda (NaHCO₃) while making cakes. She says it makes the cake soft and fluffy. Explain the chemical reaction that occurs when baking soda is heated or mixed with an acid during baking.

Q10. Why does lime water (calcium hydroxide solution) turn milky when CO₂ is passed through it? Write the chemical equation. What happens when excess CO₂ is passed?

Q11. Differentiate between baking soda and washing soda on the basis of: (i) chemical formula, (ii) preparation, and (iii) uses.

Q12. Write the chemical equation for the reaction of sulphuric acid with calcium carbonate. Why is this reaction important in the formation of caves and stalactites?

Q13. Describe the reactions of acids with metal carbonates and metal bicarbonates. Write balanced chemical equations for the reactions of HCl with Na₂CO₃, NaHCO₃, and CaCO₃. Explain the test for carbonate ions using dilute acid and limewater. How are these reactions useful in: (i) baking, (ii) fire extinguishers, and (iii) antacids?

Q14. A student is given three white powders: sodium carbonate (Na₂CO₃), sodium bicarbonate (NaHCO₃), and calcium carbonate (CaCO₃). She has dilute HCl and limewater. Help her distinguish between the three powders by:

(a) Describing the observations when each powder is treated with dilute HCl.

(b) Explaining how the rate of reaction differs between Na₂CO₃ and NaHCO₃.

(c) Describing what happens when the gas evolved is passed through limewater.

(d) Suggesting a heating test to distinguish NaHCO₃ from Na₂CO₃.

(e) Writing the chemical equation for the thermal decomposition of NaHCO₃.

Q15. "The reaction of acids with carbonates and bicarbonates is one of the most useful reactions in our daily lives, from the kitchen to the hospital." Discuss this statement by explaining: (i) how baking soda makes cakes and bread rise, (ii) how antacids containing carbonates neutralise stomach acid, (iii) the working of soda-acid fire extinguishers, and (iv) the geological significance of carbonate reactions in the formation of limestone caves.

Q16. A baker uses baking soda (NaHCO₃) to make bread. The reaction that occurs is:

2NaHCO₃ → Na₂CO₃ + H₂O + CO₂

(a) If the baker uses 16.8 g of baking soda, calculate the volume of CO₂ produced at STP. (Molar masses: NaHCO₃ = 84 g/mol; 1 mole gas at STP = 22.4 L)

(b) Calculate the mass of sodium carbonate formed.

(c) If the baker uses baking powder (which contains NaHCO₃ and an acid like tartaric acid) instead of pure baking soda, write the reaction that produces CO₂.

(d) Why is baking powder preferred over baking soda in some recipes?

(e) If a cake recipe requires 200 mL of CO₂ at STP to make the cake fluffy, calculate the mass of NaHCO₃ needed.

Q17. A soda-acid fire extinguisher contains sodium bicarbonate solution and sulphuric acid in separate compartments.

(a) Write the balanced chemical equation for the reaction when the extinguisher is activated.

(b) If the extinguisher contains 420 g of NaHCO₃, calculate the mass of H₂SO₄ needed for complete reaction. (Molar masses: NaHCO₃ = 84 g/mol, H₂SO₄ = 98 g/mol)

(c) Calculate the volume of CO₂ produced at STP from 420 g of NaHCO₃.

(d) Why is CO₂ gas used in fire extinguishers? Explain the principle.

(e) If a fire extinguisher needs to produce 50 litres of CO₂ at STP, calculate the mass of NaHCO₃ required.

Q18. The Ajanta and Ellora caves in Maharashtra are famous limestone caves formed over thousands of years by the action of carbonic acid on calcium carbonate.

(a) Write the chemical equation for the reaction of carbonic acid (H₂CO₃) with calcium carbonate (CaCO₃).

(b) If rainwater contains 0.001 M carbonic acid, calculate the mass of CaCO₃ dissolved when 1000 L of such water flows through limestone rock. (Molar mass of CaCO₃ = 100 g/mol)

(c) When this calcium bicarbonate solution drips from the cave ceiling and encounters air, CO₂ escapes and CaCO₃ is deposited, forming stalactites. Write the reverse reaction.

(d) If a stalactite grows by depositing 5 g of CaCO₃ per year, calculate how many years it would take to form a stalactite weighing 500 kg.

(e) Why is the study of carbonate chemistry important for preserving historical monuments in India?