What is observed when equal volumes of 0.1 M aqueous HCl and 0.01 M aqueous Na2SO3 are mixed?
Please explain!
(A) Colorless solution and a white precipitate
(B) Colored solution and a white precipitate
(C) Colorless solution and a colored precipitate
(D) Colorless solution, no precipitate, and gas evolution
The Correct Answer and Explanation is :
When equal volumes of 0.1 M aqueous HCl (hydrochloric acid) and 0.01 M aqueous Na2SO3 (sodium sulfite) are mixed, the observed outcome is (D) Colorless solution, no precipitate, and gas evolution.
Explanation:
- Reaction between HCl and Na2SO3:
- The Na2SO3 (sodium sulfite) dissociates in water into sodium ions (Na⁺) and sulfite ions (SO₃²⁻).
- The HCl dissociates into hydrogen ions (H⁺) and chloride ions (Cl⁻). When these two solutions are mixed, the hydrogen ions from HCl react with the sulfite ions from Na2SO3 to form sulfur dioxide (SO₂) gas, water (H₂O), and sodium chloride (NaCl) in solution. The reaction can be written as: [
\text{SO}_3^{2-} + 2\text{H}^+ \rightarrow \text{SO}_2(g) + \text{H}_2\text{O}
] This is an acid-base reaction where the sulfite ion acts as a base and reacts with the acid (H⁺) to produce sulfur dioxide gas.
- Gas Evolution:
- The reaction produces sulfur dioxide gas (SO₂), which is colorless and is released into the atmosphere as bubbles in the solution. This is the reason for gas evolution.
- No Precipitate Formation:
- The sodium chloride (NaCl) produced is highly soluble in water, so it does not form a precipitate. Additionally, no other insoluble compounds are formed in this reaction.
- Colorless Solution:
- The final solution remains colorless as neither sulfur dioxide nor the other products (NaCl, H₂O) are colored.
Thus, the final observation is a colorless solution, no precipitate, and the evolution of a gas (sulfur dioxide).
Let me generate an image to illustrate the process for you!
Here is an illustration of the laboratory setup with the reaction between aqueous HCl and Na2SO3. It shows the gas bubbles (sulfur dioxide) evolving and the colorless solution with no precipitate formed, as described in the reaction. Let me know if you need further details!
