Question

The oxidation state of Cr in $K_2Cr_2O_7 $ is

• A. 5
• B. 3
• C. 6
• D. 7

Answer 1

The Correct Option is C

To determine the oxidation state of chromium (Cr) in the compound $K_2Cr_2O_7$ (Potassium Dichromate), we use the general rules for oxidation states and calculate the unknown oxidation state. Here is the step-by-step process:

1. We know the oxidation state of potassium (K) is +1. In $K_2Cr_2O_7$, there are 2 potassium atoms. So, the total oxidation state contribution from potassium is: 2 \times (+1) = +2.
2. Oxygen (O) almost always has an oxidation state of -2. There are 7 oxygen atoms in $K_2Cr_2O_7$, so the total contribution from oxygen is: 7 \times (-2) = -14.
3. Let the oxidation state of chromium be x. Since there are 2 Cr atoms, the total contribution from chromium is: 2x.
4. The compound is neutral, so the sum of all oxidation states must be zero. Hence, we have the equation: 2(+1) + 2x + 7(-2) = 0
5. Simplifying the equation: 2 + 2x - 14 = 0
6. Solving for x: 2x - 12 = 0
7. 2x = 12
8. Divide both sides by 2: x = \frac{12}{2} = 6

Thus, the oxidation state of chromium in $K_2Cr_2O_7$ is +6. The correct option is 6.