Question

Given below are two statements.
Statement I : In H\(_2\)O\(_2\), each oxygen atom is assigned an oxidation number of -1, In RbO\(_2\), each oxygen atom is assigned an oxidation number of - \(\frac{1}{2}\).
Statement II : Representation of HAuCl\(_4\) and MnO\(_2\) in stock notation is HAu(III)Cl\(_4\) and Mn(II)O\(_2\), respectively.
Examine the above statements and choose the correct answer.

• A. Both Statement I and Statement II are correct
• B. Both Statement I and Statement II are incorrect
• C. Statement I is correct but Statement II is incorrect
• D. Statement I is incorrect but Statement II is correct

Hint:

Memorize the special cases for oxygen's oxidation number:

• \textbf{-2} in most oxides (e.g., H\(_2\)O).
• \textbf{-1} in peroxides (e.g., H\(_2\)O\(_2\)).
• \textbf{-1/2} in superoxides (e.g., KO\(_2\)).
• \textbf{+2} in OF\(_2\) (with a more electronegative element).

Answer 1

The Correct Option is C

Step 1: Analyzing Statement I.

• For H\(_2\)O\(_2\) (Hydrogen peroxide): Oxygen is in a peroxide linkage. The oxidation number of H is +1. Let the oxidation number of O be x.
  \[ 2(+1) + 2(x) = 0 \implies 2 + 2x = 0 \implies 2x = -2 \implies x = -1 \] The oxidation number of oxygen is indeed -1.
  
• For RbO\(_2\) (Rubidium superoxide): Rubidium (Rb) is an alkali metal (Group 1), so its oxidation number is +1. Let the oxidation number of O be y.
  \[ (+1) + 2(y) = 0 \implies 2y = -1 \implies y = -\frac{1}{2} \] The oxidation number of oxygen is indeed -1/2.
  

Therefore, Statement I is correct.
Step 2: Analyzing Statement II.
Stock notation represents the oxidation state of the central metal atom by a Roman numeral in parentheses.

• For HAuCl\(_4\): The oxidation number of H is +1, and Cl is -1. Let the oxidation number of Au be a.
  \[ (+1) + a + 4(-1) = 0 \implies 1 + a - 4 = 0 \implies a = +3 \] The stock notation is HAu(III)Cl\(_4\). This part of the statement is correct.
  
• For MnO\(_2\) (Manganese dioxide): The oxidation number of O is -2. Let the oxidation number of Mn be b.
  \[ b + 2(-2) = 0 \implies b - 4 = 0 \implies b = +4 \] The stock notation should be Mn(IV)O\(_2\). The statement gives Mn(II)O\(_2\), which is incorrect.
  

Since one part of Statement II is incorrect, the entire statement is incorrect.
Step 3: Final Answer.
Statement I is correct, but Statement II is incorrect.