Question

In acid medium dichromate oxidizes sulphite to sulphate as shown below. Identify correct statements about this balanced equation: 
\[ x {Cr}_2{O}_7^{2-} + y {SO}_3^{2-} + z {H}^+ \rightarrow a {Cr}^{3+} + b {SO}_4^{2-} + c {H}_2{O} \] Statements: 
I) Sum of \(x\) and \(y\) is (4) 
II) Sum of \(a\) and \(c\) is equal to \((3 + b)\). 
III) Sum of \(x\), \(y\), and \(z\) is 11.

• A. I, II, III
• B. I, II only
• C. I, III only
• D. II, III only

Hint:

Balancing redox reactions helps identify stoichiometric coefficients and verify relations between variables.

Answer 1

The Correct Option is B

Balanced reaction is:
\[ \mathrm{Cr}_2\mathrm{O}_7^{2-} + 3 \, \mathrm{SO}_3^{2-} + 8 \, \mathrm{H}^+ \rightarrow 2 \, \mathrm{Cr}^{3+} + 3 \, \mathrm{SO}_4^{2-} + 4 \, \mathrm{H}_2\mathrm{O} \]

Assign values:
\[ x = 1, \quad y = 3, \quad z = 8, \quad a = 2, \quad b = 3, \quad c = 4 \]

Check statements:
- I) \(x + y = 1 + 3 = 4\) ✓
- II) \(a + c = 2 + 4 = 6\), and \(3 + b = 3 + 3 = 6\) ✓
- III) \(x + y + z = 1 + 3 + 8 = 12 \neq 11\) ✗

Thus, only I and II are correct.