Properties of Acids and Bases (HCl & NaOH): Sodium Carbonate MCQs Quiz | Class 10

This quiz covers Class X Science (Code 086), Unit I: Practicals, focusing on the Topic: Properties of Acids and Bases (HCl & NaOH): Sodium Carbonate. It includes questions on Reaction observations and inference. Complete the quiz by selecting your answers and click “Submit Quiz” to see your score. You can also download a PDF of your answers with correct solutions.

Understanding Properties of Acids and Bases: HCl, NaOH, and Sodium Carbonate

This section dives deeper into the reactions and properties of common acids (like Hydrochloric Acid, HCl), bases (like Sodium Hydroxide, NaOH), and a crucial salt, Sodium Carbonate (Na2CO3). Understanding their interactions is fundamental in chemistry.

1. Hydrochloric Acid (HCl):

  • Nature: Strong acid.
  • Properties: Highly corrosive, readily dissolves in water to form hydronium ions (H3O+).
  • Reactions with Carbonates: Acids react with metal carbonates to produce salt, water, and carbon dioxide gas. This is a characteristic test for carbonates.
    • Reaction with Sodium Carbonate:
      Na2CO3 (s) + 2HCl (aq) → 2NaCl (aq) + H2O (l) + CO2 (g)
  • Observation: When dilute HCl is added to sodium carbonate, brisk effervescence is observed due to the rapid release of carbon dioxide gas.
  • Inference: The evolved gas turns lime water (calcium hydroxide solution) milky, confirming it as carbon dioxide.

2. Sodium Hydroxide (NaOH):

  • Nature: Strong base (alkali).
  • Properties: Highly corrosive, dissociates completely in water to produce hydroxide ions (OH-).
  • Reactions:
    • Neutralization: Reacts with acids to form salt and water.
    • With Sodium Carbonate: Sodium carbonate is a salt formed from a strong base (NaOH) and a weak acid (carbonic acid, H2CO3). Its aqueous solution is basic due to hydrolysis. Therefore, adding NaOH to Na2CO3 solution generally shows no visible reaction as both are basic or components of basic solutions.
  • Observation: No significant visible change (like effervescence or precipitate) when dilute NaOH is added to sodium carbonate solution.
  • Inference: This indicates that NaOH does not react chemically with sodium carbonate under normal conditions, as there’s no acid-base neutralization or precipitation occurring.

3. Sodium Carbonate (Na2CO3):

  • Nature: A salt, but its aqueous solution is basic. This is because it is formed from a strong base (NaOH) and a weak acid (H2CO3). When dissolved in water, the carbonate ion (CO3 2-) hydrolyzes to produce OH- ions.
  • Litmus Test: Turns red litmus blue.
  • Key Reaction: Its reaction with acids to produce CO2 gas is a defining characteristic.

Summary of Key Observations & Inferences:

Reactants Observation Inference
Dilute HCl + Sodium Carbonate Brisk effervescence (colorless, odorless gas) Carbon dioxide gas is produced; confirms carbonate.
Gas from above + Lime Water Lime water turns milky Gas is carbon dioxide.
Dilute NaOH + Sodium Carbonate No visible reaction No acid-base reaction or precipitation occurs.
Sodium Carbonate Solution + Red Litmus Red litmus turns blue Sodium carbonate solution is basic.

Quick Revision Points:

  • Acids react with carbonates to produce carbon dioxide gas.
  • Carbon dioxide gas turns lime water milky.
  • Sodium carbonate solution is basic.
  • Strong bases typically do not react visibly with other strong bases or their salts in solution.
  • pH decreases when an acid is added to a basic solution.

Practice Questions (without solutions):

  1. Describe the expected observation if magnesium carbonate is reacted with dilute sulfuric acid.
  2. Suggest a simple test to differentiate between carbon dioxide gas and hydrogen gas.
  3. Why is an aqueous solution of sodium carbonate considered basic, even though it is a salt?
  4. If a gas produced from a reaction with acid extinguishes a burning splint, what inference can be made about the gas?
  5. What would happen if blue litmus paper is dipped into a solution of sodium hydroxide?