John asks…
Using oxidation number method to balance an equation
Write a balanced equation for each of the following redox reactions using the oxidation number method.
a) Fe 2 (aq) H2O2(aq) H (aq) -> Fe 3 (aq) H2O (l)
b) Cr2O7 2- (aq) Br- (aq) H (aq) -> Cr 3 Br2 (l) H2O (l)
How do I do this? what are the steps involved?
admin answers:
This should be in the chemistry section, sorry
George asks…
What element is being oxidized/reduced and by how much does the oxidation number increase/decrease per atom?
I overall understand the redox concept but I’m not sure if I got the following reactions right:
H2O2 -> H2O + 1/2 O2
CO2 + H2O -> H2CO3
CO2 + C -> 2CO
HCl + NH3 -> NH4Cl
2ZnS + 3O2 -> 2ZnO + 2SO2
admin answers:
A) H2O2 -> H2O + 1/2 O2 O is being reduced from -1 in hydrogen peroxide to -2 in water. O is also being oxidised from -1 to 0 in the element
b) CO2 + H2O -> H2CO3 Not a redox reaction C stays at +4 and O stays at -2 (the CO3 carbonate ion is 2-)
c)CO2 + C -> 2CO The C is being reduced from +4 to +2. The carbong is also being oxidised from 0 in the element to +2
d) HCl + NH3 -> NH4Cl This is not a redox reaction the oxidation numbers are as follows N+3, H+1, Cl-1
e) 2ZnS + 3O2 -> 2ZnO + 2SO2 The Zn remains the same but the S goes from -2 to -4, the O goes from 0 in the element to -2.
Notes c is the a disproportionation (both oxidation and reduction of same element) in reverse.
A is a disproportionation
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