What is the oxidation state of chromium (Cr) in the compound K2Cr2O7?

• A. +7
• B. +3
• C. +6
• D. +2

Answer: (C)

Verified step by step guidance

1. Identify the elements and their typical oxidation states in the compound K2Cr2O7. Potassium (K) is an alkali metal and usually has an oxidation state of +1, and oxygen (O) typically has an oxidation state of -2.
2. Write the overall charge balance equation for the compound. Since K2Cr2O7 is neutral, the sum of the oxidation states of all atoms must equal zero.
3. Express the total oxidation state contribution from potassium and oxygen: For 2 potassium atoms, the total is \$2 \times (+1) = +2\(, and for 7 oxygen atoms, the total is \)7 \times (-2) = -14$.
4. Let the oxidation state of chromium be \(x\). Since there are 2 chromium atoms, their total contribution is \$2x\(. Set up the equation for the sum of oxidation states: \)2(+1) + 2x + 7(-2) = 0$.
5. Solve the equation for \(x\) to find the oxidation state of chromium: \$2 + 2x - 14 = 0\( which simplifies to \)2x - 12 = 0\(, and then \)2x = 12\(, so \)x = +6$.