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