In qualitative analysis, dichromate ions (Cr2O72–) are commonly used as oxidizing agents. Reduction of these ions often results in a color change, which can help identify the reducing species.
Step 1: Reaction Involved
When \(\text{SO}_3^{2-}\) reacts with dilute \(\text{H}_2\text{SO}_4\), \(\text{SO}_2\) gas is evolved. The \(\text{SO}_2\) gas reduces the dichromate ion (\(\text{Cr}_2\text{O}_7^{2-}\)) to \(\text{Cr}^{3+}\), which is green in color. The reaction is as follows:
\[\text{Cr}_2\text{O}_7^{2-} + \text{SO}_3^{2-} + \text{H}^+ \rightarrow \text{Cr}^{3+} + \text{SO}_4^{2-}.\]
Step 2: Color Change
- Dichromate ion (\(\text{Cr}_2\text{O}_7^{2-}\)) is orange in color.
- After reduction, \(\text{Cr}^{3+}\) ions form, which are green in color.
Conclusion: The solution turns green due to the formation of \(\text{Cr}^{3+}\). Therefore, the correct answer is \((3)\) Green.
For a reaction, \[ {N}_2{O}_5(g) \rightarrow 2{NO}_2(g) + \frac{1}{2} {O}_2(g) \] in a constant volume container, no products were present initially. The final pressure of the system when 50% of the reaction gets completed is:
In Carius method for estimation of halogens, 180 mg of an organic compound produced 143.5 mg of AgCl. The percentage composition of chlorine in the compound is ___________%. [Given: Molar mass in g mol\(^{-1}\) of Ag = 108, Cl = 35.5]
If \[ \frac{dy}{dx} + 2y \sec^2 x = 2 \sec^2 x + 3 \tan x \cdot \sec^2 x \] and
and \( f(0) = \frac{5}{4} \), then the value of \[ 12 \left( y \left( \frac{\pi}{4} \right) - \frac{1}{e^2} \right) \] equals to: