Question

The correct decreasing order of oxidation state of the underlined atom in each molecule is

• A. \(P_4O_{10} \gt Cl_2O_7 \gt AlH_3\)
• B. \(P_4O_{10} \gt SO_3 \gt H_2O\)
• C. \(N_2O_5 \gt Al_2O_3 \gt H_2S\)
• D. \(PbO_2 \gt N_2O_3 \gt SO_3\)

Hint:

For neutral compounds, the algebraic sum of oxidation numbers of all atoms is always zero. Use this rule systematically to determine unknown oxidation states.

Answer 1

The Correct Option is C

Step 1: Plan the approach.
We assign oxidation numbers using O as \(-2\) and H as \(+1\), then sort the underlined atoms in the correct option.
Step 2: Nitrogen in \(N_2O_5\).
\[ 2x + 5(-2) = 0 \implies 2x = 10 \implies x = +5. \]
Step 3: Aluminium in \(Al_2O_3\).
\[ 2x + 3(-2) = 0 \implies 2x = 6 \implies x = +3. \]
Step 4: Sulphur in \(H_2S\).
\[ 2(+1) + x = 0 \implies x = -2. \]
Step 5: Rank the values.
\(+5 > +3 > -2\).
Step 6: Write the decreasing order.
This corresponds to \(N_2O_5 > Al_2O_3 > H_2S\).
\[ \boxed{N_2O_5 > Al_2O_3 > H_2S} \]