What is the oxidation state of chromium in K2Cr2O7?

• A. +7
• B. +2
• C. +3
• D. +6

Answer: (D)

Verified step by step guidance

1. Identify the overall charge of the compound K2Cr2O7, which is neutral (0).
2. Assign the known oxidation states: potassium (K) is always +1, and oxygen (O) is usually -2.
3. Set up an equation to represent the sum of oxidation states: 2 potassium atoms contribute 2(+1) = +2, 7 oxygen atoms contribute 7(-2) = -14, and 2 chromium atoms have an unknown oxidation state x each, so total from chromium is 2x.
4. Write the equation for the sum of oxidation states: 2(+1) + 2x + 7(-2) = 0, which simplifies to 2 + 2x - 14 = 0.
5. Solve the equation for x: 2x - 12 = 0, so 2x = 12, and x = +6, which is the oxidation state of chromium in K2Cr2O7.