Question

What is the oxidation number of chromium in k2cr2o7

Answer 1

Answer:

• The oxidation state of chromium in K₂Cr₂O₇ is 6⁺ (i.e. + 6).

Explanation:

You can calculate the oxidation number of most elements following some simple rules.

This is how you do it for chromium in K₂Cr₂O₇.

1) Rule: in a neutral compound the net oxidation number is zero (0).

Hence, sum of the oxidation numbers of K, Cr and O in K₂Cr₂O₇ is 0.

2) Rule: The most common oxidation number of oxygen in compounds, except in peroxides, is  2 ⁻ (negative 2).

3) Rule: the most common oxidation state of alkali metals is 1⁺ (positive 1)

4) Rule: multiply each oxidation state by the corresponding number of atoms in the compound (the subscripts)

• 2(1⁺) + 2(x) + 7(2⁻) = 0

          ↑         ↑       ↑

          K        Cr      O

• 2 + 2x - 14 = 0

• 2x - 12 = 0

• 2x = 12

• x = 6

Hence, the oxidation number of chromium in this compound is 6⁺.