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Report Thread starter 2 years ago
Which of these is not a redox reaction?[1 mark]
A) Cu2O +H2SO4→ CuSO4+Cu +H2O
B) MgO +2HCl→ MgCl2+H2O
C) SnCl2+HgCl2→ Hg +SnCl4
D) MnO2+4HCl→ MnCl2+2H2O +Cl

anyone know how to go about working this out?
Badges: 8
Report 2 years ago
Rule 1: For compounds, the sum of the oxidation states (all the individual ox states added up) must equal to charge of the compound.
Rule 2: elements have ox states = 0
Rule 3: Oxygen has ox states of -2 always unless in hydrogen peroxide (H2O2)
Rule 4: Hydrogen has ox state of +1 always unless in metal hydrides (MH) where M is a metal)
Use these rules to determines the ox states of al species and compounds. With this information, you can clearly see which species are oxidising ( ox states decreases) or is reduced (ox states increases) as by definition ox states is the total no of electron gained or donated by a species.

eg: Cu2O>>>>> since following rule 3 ox state of Oxygen is -2 and following rule 1 ox state of the whole ionic compound is 0 as its charge is neutral (0) so we can say Cu2O>>> Cu2+-2=0
Cu= +1 (must find ox states of 1 mole of each element)
Here we GO>>>>>

A) Cu2O +H2SO4→ CuSO4+Cu +H2O
(1,-2) (1,6,-2) (2,6,-2) (0) (1,-2) Cu is reduced and oxidised and so is redox reaction (where 1 species reduces and oxides simultaneously called a disproportionation reaction)

B) MgO +2HCl→ MgCl2+H2O
(1,-2) (1,-1) (1,-1) (1,-2) no change is ox states so not redox

C) SnCl2+HgCl2→ Hg +SnCl4
(2,-1) (2,-1) (0) (4,-1) Sn is reduced and Hg is oxidised so there is a change in ox states so redox reaction

D) MnO2+4HCl→ MnCl2+2H2O +Cl
(4,-2) (1,-1) (2,-1) (1,-2) (0) Mn is oxsided and Cl reduced is their is a change in ox states so redox reaction

Hope this Helps

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