Question

Species "X" is dissolved in \( \mathrm{H_2SO_4} \) and reacts with \( \mathrm{SO_2} \) to give a green color solution. The species "X" is:

• A. \( \mathrm{KMnO_4} \)
• B. \( \mathrm{K_2Cr_2O_7} \)
• C. \( \mathrm{Pb(CH_3COO)_2} \)
• D. \( \mathrm{KI} \)

Hint:

When \( \mathrm{SO_2} \) reacts with oxidizing agents like \( \mathrm{K_2Cr_2O_7} \), the chromium species are reduced to \( \mathrm{Cr^{3+}} \), which forms a green-colored solution.

Answer 1

The Correct Option is B

Step 1: Understanding the reaction of species with \( \mathrm{SO_2} \).
When \( \mathrm{SO_2} \) (sulfur dioxide) reacts with an oxidizing agent, the species is reduced, and a color change is observed. The green color typically arises when chromium species are reduced from \( \mathrm{Cr_2O_7^{2-}} \) to \( \mathrm{Cr^{3+}} \), which is green.

Step 2: Identify the species that would give a green color with \( \mathrm{SO_2} \).
- \( \mathrm{KMnO_4} \) (Potassium permanganate) is purple in color and is not known to give a green color solution when reacting with \( \mathrm{SO_2} \). - \( \mathrm{K_2Cr_2O_7} \) (Potassium dichromate) is orange and can be reduced to \( \mathrm{Cr^{3+}} \), which gives a green solution in the presence of \( \mathrm{SO_2} \). - \( \mathrm{Pb(CH_3COO)_2} \) (Lead acetate) does not typically react with \( \mathrm{SO_2} \) to give a green color. - \( \mathrm{KI} \) (Potassium iodide) does not react with \( \mathrm{SO_2} \) to form a green solution, as it is a reducing agent but does not lead to a green color change.
Step 3: Conclusion.
Thus, the species "X" that reacts with \( \mathrm{SO_2} \) to give a green color solution is \( \mathrm{K_2Cr_2O_7} \) (Potassium dichromate).
Final Answer: \( \mathrm{K_2Cr_2O_7} \)