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A dilute solution of sodium carbonate was added to two test tubes one containing dilute HCI (A) and the other containing dilute NaOH (B). the correct observation was:

A dilute solution of sodium carbonate was added to two test tubes one containing dilute HCI (A) and the other containing dilute NaOH (B). the correct observation was: Correct Answer A colorless gas liberated in test tube A

Concept:

  • Sodium carbonate with the molecular formula Na2CO3 is a basic salt.
  • It is a salt of a weak acid and a strong base. It is prepared via the Solvay process.
  • Hydrated Sodium Carbonate is known as Washing Soda with the formula Na2CO3. 10H2O.
  • Sodium Carbonate is a white crystalline solid and is soluble in water.
  • Sodium carbonate is hygroscopic in nature.
  • It dissolves readily in water to give NaOH and Carbonic acid H2CO3. Thus its aqueous solution is basic in nature.
  • Sodium carbonate solution reacts violently with acids.

Explanation:

Set up A:

  • Sodium Carbonate solution is taken and dilute HCl is added to it.
  • The reaction taking place is:

Na2CO3 + 2HCl → 2NaCl + CO2 + H2O

  • As the solution of sodium carbonate is basic, it reacts with dilute acid HCl.
  • A brisk effervescence is seen and colourless gas CO2 is produced. The gas turns lime water milky.

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Set up B:

  • Sodium Carbonate solution is taken and dilute NaOH is added to it.
  • As Sodium carbonate solution is basic, it does not react with base NaOH.
  • Hence, no gases are evolved in the reaction.

Hence, only colourless gas is evolved in test tube A.

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