What is the oxidation state of cr in crpo4 and cr3(po4)2?

Explanation:

Oxidation state of Cr in CrPO₄

As a general rule, the algebraic sum of all the oxidation numbers of all atoms in a neutral compound is zero.

The compound above is in its neutral state and we sum all the oxidation numbers and equate to zero:

The oxidation number of P is -2

                                           O is -2

Let the oxidation number of Cr be x:

                              x + (-2) + 4(-2) = 0

                              x -2-8 = 0

                               x -10 = 0

                                x = +10

For Cr in Cr₃(PO₄)₂

         Using the same rule:

        2(x) + 2[-2 + 4(-2)] = 0

           2x + 2(-2-8) = 0

            2x -20 = 0

                x = +10