Cr in Cr2O7 -2 what is the oxidation number

oxidation-number

#1

Cr in Cr2O7 -2 what is the oxidation number

Answer:

Start by writing your charge balance equation (there are two unknowns so “X” is the oxidation number of Cr and Y of Oxygen.
-2[Cr2O7] = X[Cr] + Y[O]
fill in the quantities for each species
-2[1] = X[2] + Y[7]
Oxygen has an oxidation number of -2 in all but a few rate cases so it is safe to assume it into the equation.
-2[1] = X[2] + -2[7]
-2 = X[2] + (-14)
X[2] = -2 - (-14)
X = 12/2
X=6
+6 is the oxidation number of Cr.