Question

What is the oxidation state of chromium in \( \text{K}_2\text{Cr}_2\text{O}_7 \)?

• A. +2
• B. +3
• C. +6
• D. +7

Hint:

Remember: The oxidation state of oxygen is usually \( -2 \), and the oxidation state of alkali metals like potassium is \( +1 \). Use the sum of oxidation states to find the unknown oxidation state.

Answer 1

The Correct Option is C

Step 1: Assign oxidation states to known elements In \( \text{K}_2\text{Cr}_2\text{O}_7 \), the oxidation state of potassium \( K \) is \( +1 \) and the oxidation state of oxygen \( O \) is \( -2 \). Step 2: Set up the equation for the sum of oxidation states Let the oxidation state of chromium be \( x \). The sum of the oxidation states in \( \text{K}_2\text{Cr}_2\text{O}_7 \) must equal zero because it is a neutral compound. \[ 2(\text{oxidation state of K}) + 2(\text{oxidation state of Cr}) + 7(\text{oxidation state of O}) = 0 \] Substituting the known oxidation states: \[ 2(1) + 2(x) + 7(-2) = 0 \] \[ 2 + 2x - 14 = 0 \] \[ 2x - 12 = 0 \] \[ 2x = 12 \] \[ x = 6 \] Answer: Therefore, the oxidation state of chromium in \( \text{K}_2\text{Cr}_2\text{O}_7 \) is +6. So, the correct answer is option (3).