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# Redox question Watch

1. Chlorine gas may be prepared in the laboratory by reacting hydrochloric gas with potassium manganate (VII). The following standard electrode potentials relate to this reaction.

1/2 Cl2 + e- --> Cl- (E = +1.36V)

MnO4- + 8H+ + 5e- --> Mn2- + 4H20 (E = +1.52)

c) Use the half equations above to construct an ionic equation for the reaction between hydrochloric acid and potassium manganate (VII)

I got the answer of:

MnO4- + 5Cl- + 8H+ --> 2.5Cl2 + Mn2+ + 4H20

According to the mark scheme, the answer is:

2MnO4- + 10Cl- + 16H+ --> 5Cl2 + 2Mn2+ + 8H20

Does it matter that everything is doubled? Why have they done this?
2. You still get the marks, its just that ms had it as whole numbers and multiplied by 2 if you open other ms you might find it the oppposite they dont multiply by 2 , but the point is they are both accepted.
3. (Original post by BethMay17)
Chlorine gas may be prepared in the laboratory by reacting hydrochloric gas with potassium manganate (VII). The following standard electrode potentials relate to this reaction.

1/2 Cl2 + e- --> Cl- (E = +1.36V)

MnO4- + 8H+ + 5e- --> Mn2- + 4H20 (E = +1.52)

c) Use the half equations above to construct an ionic equation for the reaction between hydrochloric acid and potassium manganate (VII)

I got the answer of:

MnO4- + 5Cl- + 8H+ --> 2.5Cl2 + Mn2+ + 4H20

According to the mark scheme, the answer is:

2MnO4- + 10Cl- + 16H+ --> 5Cl2 + 2Mn2+ + 8H20

Does it matter that everything is doubled? Why have they done this?
You still get the marks, as long as they are multiples, its still correct, e.g. all double or triple
4. it's fine, they just multiplied everything by 2 so that everything is in whole numbers

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