Question

The oxidation states of sulphur in the anions $SO _{3}{ }^{2-}, S _{2} O _{4}{ }^{2-}$ and $S _{2} O _{6}{ }^{2-}$ follow the order -

• A. $S_2O_4^{ 2 - } < S_2O_6^{ 2 - } < SO_3^{ 2 - }$
• B. $S_2O_6^{ 2 - } < S_2O_4^{2 - } < SO_3^{ 2 - }$
• C. $S_2O_4^{ 2 - } < SO_3^{ 2 - } < S_2O_6^{ 2 - }$
• D. $SO_3^{ 2 - } < S_2O_4^{ 2 - } < S_2O_6^{ 2 - }$

Answer 1

The Correct Option is C

To determine the order of oxidation states of sulfur in the anions \(SO_3^{2-}\), \(S_2O_4^{2-}\), and \(S_2O_6^{2-}\), we need to calculate the oxidation state of sulfur in each compound individually.

1. Oxidation state of S in \(SO_3^{2-}\):
   • The formula of the sulfate ion is \(SO_3^{2-}\).
   • Let the oxidation state of sulfur be \(x\).
   • Oxygen generally has an oxidation state of \(-2\). Hence, for three oxygen atoms: \(3 \times (-2) = -6\).
   • According to the charge on the ion, \(x + (-6) = -2\).
   • Solving for \(x\): \(x = -2 + 6 = +4\).
2. Oxidation state of S in \(S_2O_4^{2-}\):
   • The formula of the dithionite ion is \(S_2O_4^{2-}\).
   • Let the oxidation state of sulfur be \(x\).
   • Oxygen has \(-2\) as its oxidation state. Therefore, for four oxygen atoms: \(4 \times (-2) = -8\).
   • From the charge on the ion, \(2x + (-8) = -2\).
   • Solving for \(x\): \(2x = -2 + 8 = 6\), thus \(x = \frac{6}{2} = +3\).
3. Oxidation state of S in \(S_2O_6^{2-}\):
   • The formula of the dithionate ion is \(S_2O_6^{2-}\).
   • Let the oxidation state of sulfur be \(x\).
   • Oxygen's oxidation state is \(-2\). For six oxygens: \(6 \times (-2) = -12\).
   • According to the charge balance, \(2x + (-12) = -2\).
   • Solving for \(x\): \(2x = -2 + 12 = 10\), hence \(x = \frac{10}{2} = +5\).

With the calculated oxidation states, the order is determined based on their numerical values:

\(S_2O_4^{2-}\) with oxidation state of \(+3\), \(SO_3^{2-}\) with \(+4\), and \(S_2O_6^{2-}\) with \(+5\).

Thus, the correct order of oxidation states for sulfur in the given anions is:

S_2O_4^{ 2 - } < SO_3^{ 2 - } < S_2O_6^{ 2 - }