Question

What is the oxidation state of chromium in Cr(H2O)6 (3+)?

Answer 1

The oxidation state of Cr in Cr(H₂O)₆³⁺ is +3.

Let's recall some of the rules for calculating oxidation states.

• The oxidation state of O is almost always -2.
• The oxidation state of H is almost always +1.
• The sum of all the oxidation states equals the charge on the ion.

If H = +1, then 2H = +2. If O = -2, then 2H + O = +2 - 2 = 0.

Thus, the H₂O units do not contribute to the charge on the ion. The only atom that contributes is the Cr atom.

Since the charge on the ion is 3+, the oxidation state of Cr is +3.