What are the oxidation numbers of each element (see details)?

Question

please assign the oxidation number for each element in the equation....

1. K2Cr2O7 H2O S ---> KOH Cr2O3 SO2

2. NO3 H2S ---> S NO H2O

thanks..... ^^

Answer 1

K2Cr2O7

            K =+1

           Cr=+6

            O = -2

   H2O

           H=+1

          O  = -2

        S   =  0

    KOH

         K=+1

        O=-2

        H=  +1

   Cr2O3

       Cr = +3

    NO3

        H2S

          S  = -2

       S = 0

     NO

      N = +3

       O=  -2

    

Answer 2

1) For K2Cr2O7

K= +1 Cr= +6 O= -2

H20

H= +1 O= -2

S= 0

For KOH

k= +1 O= -2 H= +1

for Cr2O3

Cr= +3

O= -2

For S02

S= +4 O= -2

2) For NO3

N= +6 O= -2

For H2S

H= +1

S= -2

For S = 0

for NO

N= +2

O= -2

for H20

H= +1 O= -2

Answer 3

To assign oxidation numbers you can use a few general rules:

All elements in their elemental state = 0

Oxygen is usually -2 (except in peroxides)

Hydrogen is + or -1

Alkali metals are always +1

Alkaline earth metals are +2

Halogens, if written last (very important) are -1

The total charge of a compound always = 0

If you use these rules you can figure out the Cr in K2Cr2O7 is +6

(K = +1 x 2, O = -2 x 7 so BOTH Cr must be +12 to make the compound neutral, so EACH Cr must be +6)

On the reactant side the S = 0; in the SO2 the S = +4 because the 2 oxygen = -4

You should be able to take it from there