[tharox97]

this is my question:

50cm3 of 0.1M solution of Metallic salt reacted exactly with 25cm3 of 0.1M aqueous sodim sulfite, Na2SO3
a)half equation for oxidation of the sulfite, to SO4^2-
b)if the original oxidation number of the metal in the salt was +3, what would be the new oxidation number of the metal after after reaction with Na2SO3?
 
i got part a pls help with part b
pls help me. Thanks in advance

Ans for part b is +2 btw

[Dan]

You must show you have attempted the question, it is a Forum Rule. In addition, please format your formulae properly and avoid chat room abbreviations.

From part a), you should have worked out how many electrons are involved in the oxidation of sulfite.

The stoichiometry of the reaction (ratio of metal to sulfite) is given (or can be deduced) from the opening of the question.

If you combine these pieces of information, you should be able to find the answer. Post your attempt and we'll take it from there.

[tharox97]

part a) is SO3^2- + H2O = SO4^2-+ 2H^+ + 2e

part b) from the information given, Na2SO3 is 0.0025mol, the metallic salt is 0.005mol
           
           from here i do not know how to link the moles to the oxidation numbers
           
thanks for your reply DAN

[tharox97]

You must show you have attempted the question, it is a Forum Rule. In addition, please format your formulae properly and avoid chat room abbreviations.

From part a), you should have worked out how many electrons are involved in the oxidation of sulfite.

The stoichiometry of the reaction (ratio of metal to sulfite) is given (or can be deduced) from the opening of the question.

If you combine these pieces of information, you should be able to find the answer. Post your attempt and we'll take it from there.

part a) is SO3^2- + H2O = SO4^2-+ 2H^+ + 2e

part b) from the information given, Na2SO3 is 0.0025mol, the metallic salt is 0.005mol
           
           from here i do not know how to link the moles to the oxidation numbers
           
thanks for your reply DAN

[sjb]

part a) is SO3^2- + H2O = SO4^2-+ 2H^+ + 2e

part b) from the information given, Na2SO3 is 0.0025mol, the metallic salt is 0.005mol
           
           from here i do not know how to link the moles to the oxidation numbers
           
thanks for your reply DAN

So what's the ratio of salt to sulfite?

[tharox97]

2:1

[sjb]

2:1

So, if sulfite requires two electrons to oxidise it, how many electrons does the metal salt need to reduce it?