Redox reactions

Occam's Razor SG

Which of the reactions are redox reactions?

1) CO2 + C -> 2CO
2) 2Fe + 3Cl2 -> 2FeCl3
3)CuCO3 -> CuO + CO2
4) H2O + SO3 -> H2SO4

Im not sure about 3) and 4), but for 1) and 2) I think they are redox. Can anyone please help me? Thanks.

arigatoast SG

1) CO2 is reduced to CO and C is oxidised to CO . so redox.

2) Fe o.s from 0 to +3 = oxidation

Cl o.s from 0 to -1 = reduction.

so 2) is redox

3) C o.s +4 nv change.

O o.s is -2 nv change

Cu o.s +2 nv change

so not redox

4) H o.s +1 nv change

O o.s -2 nv change

S o.s +6 nv change.

so not redox

Occam's Razor SG

Thanks!