Question

identify the oxidation number of chromium in the dichromate ion. ? cr₂o₇²⁻ 1. +6 2. +7 3. +12 4. +14 enter the answer choice number.

Explanation:

Step1: Recall oxidation number rules

Oxygen usually has an oxidation number of -2 (except in peroxides, etc.). The dichromate ion has a charge of -2. Let the oxidation number of Cr be \( x \).

Step2: Set up the equation

For \( \text{Cr}_2\text{O}_7^{2-} \), we have \( 2x + 7\times(-2) = -2 \).

Step3: Solve the equation

\( 2x - 14 = -2 \)
\( 2x = -2 + 14 \)
\( 2x = 12 \)
\( x = \frac{12}{2} = +6 \). So the oxidation number of Cr is +6, which corresponds to option 1.

Answer:

1