Question

Oxidation state of Cr in potassium dichromate is

• A. +7
• B. +6
• C. +1
• D. +5

Hint:

Chromium frequently appears in standard exam questions in two main forms: Chromate ($\text{CrO}_4^{2-}$) and Dichromate ($\text{Cr}_2\text{O}_7^{2-}$). In both of these common oxidizing agents, Chromium is always in the $+6$ oxidation state!

Answer 1

The Correct Option is B

Step 1: Write the formula.
Potassium dichromate is $\text{K}_2\text{Cr}_2\text{O}_7$. The charges must sum to zero.

Step 2: Set up the sum.
With K as $+1$ and O as $-2$, let Cr be $x$: $2(+1) + 2x + 7(-2) = 0$.

Step 3: Solve.
$$2 + 2x - 14 = 0 \Rightarrow 2x = 12 \Rightarrow x = +6$$
\[ \boxed{+6} \]