Question

What is the oxidation number of Cr in K\(_2\)Cr\(_2\)O\(_7\)?

• A. +2
• B. +12
• C. -6
• D. +6

Hint:

To find the oxidation state of an element in a compound, use the charge balance method and the known oxidation states of other elements in the compound.

Answer 1

The Correct Option is D

Step 1: Understanding the structure of the compound.
In potassium dichromate (K\(_2\)Cr\(_2\)O\(_7\)), potassium (K) has an oxidation state of +1, and oxygen (O) has an oxidation state of -2. We can use this information to calculate the oxidation number of chromium (Cr).

Step 2: Applying the charge balance.
The sum of oxidation states must be zero for the neutral compound. For K\(_2\)Cr\(_2\)O\(_7\), we write the equation for the sum of oxidation states: \[ 2 \times (+1) + 2 \times x + 7 \times (-2) = 0 \] where \(x\) is the oxidation state of Cr. Solving for \(x\), we get: \[ 2 + 2x - 14 = 0 \quad \Rightarrow \quad 2x = 12 \quad \Rightarrow \quad x = +6 \]
Step 3: Conclusion.
The oxidation number of Cr in K\(_2\)Cr\(_2\)O\(_7\) is (D) +6.