Question

What is the oxidation state of chromium in K₂Cr₂O₇?

• A. +6
• B. +3
• C. +2
• D. 0

Hint:

In ionic compounds, the sum of the oxidation states of all elements equals the net charge of the molecule. Use this principle to find unknown oxidation states.

Answer 1

The Correct Option is A

Potassium dichromate (\( \text{K}_2\text{Cr}_2\text{O}_7 \)) requires the determination of the oxidation state of chromium (\( \text{Cr} \)). The following steps are applied:
1. Assign known oxidation states: - Potassium (\( \text{K} \)) is \( +1 \) (alkali metal). - Oxygen (\( \text{O} \)) is \( -2 \) (standard in most compounds). 2. Formulate the equation for the neutral compound: - Let \( x \) be the oxidation state of chromium. - The sum of oxidation states for \( \text{K}_2\text{Cr}_2\text{O}_7 \) is: \[ 2 \times (+1) + 2x + 7 \times (-2) = 0 \] Simplify the equation: \[ 2 + 2x - 14 = 0 \] \[ 2x = 12 \] \[ x = +6 \] 3. Conclusion: - The oxidation state of chromium in \( \text{K}_2\text{Cr}_2\text{O}_7 \) is \( +6 \).