Question

Chapter 19, Question 2Determine the oxidation state of the transition metal in each compound.

a) NiSO4

b) KMnO₄

c) (NH₄)₂WO₄

d) What is the oxidation state of Pb in PbCrO₄?

e) What is the oxidation state of Cr in PbCrO₄?

f) ZrOCl2.8H2O

Answer 1

a)
NiSO4 is compound of Ni2+ and SO42-
So,
Oxidation state of Ni is +2
Answer: +2

b)
Oxidation number of K = +1
Oxidation number of O = -2

lets the oxidation number of Mn be x

use:
1* oxidation number (K) + 4* oxidation number (O) + 1* oxidation number (Mn) = net charge
1*(+1)+4*(-2)+1* x = 0
-7 + 1 * x = 0
x = 7
So oxidation number of Mn = +7
Answer: +7

c)
Oxidation number of O = -2
Oxidation number of H = +1
Oxidation number of N = -3

lets the oxidation number of W be x

use:
2* oxidation number (N) + 8* oxidation number (H) + 4* oxidation number (O) + 1* oxidation number (W) = net charge
2*(-3)+8*(+1)+4*(-2)+1* x = 0
-6 + 8 - 8 + x = 0
x = +6
So oxidation number of W = +6
Answer: +6

d)
PbCrO4 is compound of Pb2+ and CrO4-2
Oxidation state of Pb is +2
Answer: +2

e)
In CrO4-2:

Oxidation number of O = -2

lets the oxidation number of Cr be x

use:
4* oxidation number (O) + 1* oxidation number (Cr) = net charge
4*(-2)+1* x = -2
-8 + 1 * x = -2
x = 6
So oxidation number of Cr = +6

Answer: +6

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