Originally posted by 787180:Iron(11) sulphate is a reducing agent containing Fe 2+ and SO4 .how to plan an experiment to prove it is the Fe 2+ ion and not the SO4 ion that acts as the reducing agent.Pl help?
Your question is vague. You need to be more specific, by describing the exact experiment details.
For instance, if you observe a colour change from dark green / pale green to reddish-brown / yellow, which is indicative of the oxidation of Fe(HO)2(s) / Fe2+(aq) to Fe(OH)3(s) / Fe3+(aq), then you may argue that since Fe2+ is oxidized to Fe3+, the electrons lost must have been used for reduction.
You would also have to test for the presence of SO4 2- or sulfate(VI) ion, to show that it remained chemically unchanged. If your experimental observations indicate production of other sulfur componds of varying oxidation states (eg. thiosulfate ion, tetrathionate ion, sulfate(IV) ion, sulfur dioxide, hydrogen sulfide, etc), then based on the change in oxidation state, you may ascertain if the sulfate(VI) ion was oxidized or reduced, and therefore, whether it was the reducing agent or oxidizing agent, if either.
Btw, I expect you know you have to add aqueous sodium hydroxide to the iron(II) sulfate (before redox) / iron(III) sulfate (after redox) solution, to demonstrate by the colour of the ppt formed (dark green Fe(OH)2(s) vs reddish-brown Fe(OH)3(s)) upon adding NaOH(aq) that Fe2+ is oxidized to Fe3+ and hence Fe2+ is the reducing agent.
I think in this question there is a need to provide another reagent, it is impossible to tell wheter A is a oxidising agent where there is only A involved
But in my opinion, since a oxidising agent is one that get reduced, Fe2+ had a better chance of being the oxidising agent as the oxidation state is +2 as compared to -2 in (SO42-).
However, can add sutible reagent to Iron (II) Sulphate and isolate one product to the other, and test using aqueous potassium dichromate and potassium ioidide, then, if one of the product, perfrably the one with the Iron (II) ion is reduced and the other is unchanged, Iron (II) is the reducing agent
correct me if i am wrong
Originally posted by SBS n SMRT:I think in this question there is a need to provide another reagent, it is impossible to tell wheter A is a oxidising agent where there is only A involved
But in my opinion, since a oxidising agent is one that get reduced, Fe2+ had a better chance of being the oxidising agent as the oxidation state is +2 as compared to -2 in (SO42-).
However, can add sutible reagent to Iron (II) Sulphate and isolate one product to the other, and test using aqueous potassium dichromate and potassium ioidide, then, if one of the product, perfrably the one with the Iron (II) ion is reduced and the other is unchanged, Iron (II) is the reducing agent
correct me if i am wrong
>>> Fe2+ had a better chance of being the oxidising agent as the oxidation state is +2 as compared to -2 in (SO42-). <<<
The IONIC CHARGE of the dinegative sulfate(VI) ion is 2-. It's incorrect (and a common student error) to say "the O.S. of a dinegative ion is -2". The O.S. must always refer to the O.S. of an ELEMENT (or a specified atom of an element, if the Kekule structure is drawn) within a specified compound.
Eg. O.S. of SULFUR in the following compounds are (to properly understand this business of O.S. and it's relationship to formal charges and electronegativity, draw the Kekule structures) :
sulfur dioxide hydrolyzed to sulfate(IV) ion SO3 2- ----> +4
sulfur trioxide hydrolyzed to sulfate(VI) ion SO4 2- ----> +6
thiosulfate ion S2O3 2- ----> +2 (average of), +4 and 0.
tetrathionate ion S4O6 2- ----> +2.5 (average of), +5, 0, 0, +5.
peroxydisulfate(VI) ion S2O8 2- ----> +6
(6 oxygen atoms have O.S. of -2 each, the 2 oxygen atoms of the peroxy group have O.S. of -1 each).
Originally posted by 787180:Thks for all the replies(v helpful indeed).Can give me one reagent to use for such test?
Use aqueous sodium hydroxide to precipitate out Fe2+ and Fe3+ as Fe(OH)2(s) and Fe(OH)3(s), which are dark/dirty-green and reddish-brown respectively.
As for the reagent to be reduced (by Fe2+), use a suitable oxidizing agent, eg. acidified KMnO4(aq) which is purple, and when reduced (by Fe2+) will become colourless Mn2+(aq).
O.S. of Mn is decreased from +7 (in MnO4-) to +2 (in Mn2+).
Note that in neutral or alkaline conditions, with insufficient molarity of protons [H+], a brown ppt of MnO2(s) (stock name manganese(IV) oxide) will be obtained, instead of colourless Mn2+(aq).
(edited out a precious hint to my Chemistry Challenge Qn aka Calvin's Cunningly Cryptic Chemistry Conundrum Challenge)
Originally posted by 787180:Iron(11) chloride soln reacts with acidified KMnO4
5Fe2+(aq) 8H(aq) + MnO4(aq0—-5Fe3+(aq)Mn2(aq)+4H2O(L).Can U find a parallel with iron(11) sulphate soln?.Thks in advance
[Reduction] MnO4– + 8H+ + 5e– --> Mn2+ + 4H2O
[Oxidation] 5Fe2+ --> 5Fe3+ + 5e-
[Balanced Redox] 5Fe2+ + MnO4– + 8H+ --> Mn2+ + 4H2O + 5Fe3+
The sulfate ions are spectator ions, and hence are not included in the balanced redox equation.
Originally posted by UltimaOnline:
>>> Fe2+ had a better chance of being the oxidising agent as the oxidation state is +2 as compared to -2 in (SO42-). <<<
The IONIC CHARGE of the dinegative sulfate(VI) ion is 2-. It's incorrect (and a common student error) to say "the O.S. of a dinegative ion is -2". The O.S. must always refer to the O.S. of an ELEMENT (or a specified atom of an element, if the Kekule structure is drawn) within a specified compound.
Eg. O.S. of SULFUR in the following compounds are (to properly understand this business of O.S. and it's relationship to formal charges and electronegativity, draw the Kekule structures) :
sulfur dioxide hydrolyzed to sulfate(IV) ion SO3 2- ----> +4
sulfur trioxide hydrolyzed to sulfate(VI) ion SO4 2- ----> +6
thiosulfate ion S2O3 2- ----> +2 (average of), +4 and 0.
tetrathionate ion S4O6 2- ----> +2.5 (average of), +5, 0, 0, +5.
peroxydisulfate(VI) ion S2O8 2- ----> +6
(6 oxygen atoms have O.S. of -2 each, the 2 oxygen atoms of the peroxy group have O.S. of -1 each).
thanks
so the o.s of (SO4)2- is for sulphur -10 and for oxygen is -1??
Originally posted by SBS n SMRT:thanks
so the o.s of (SO4)2- is for sulphur -10 and for oxygen is -1??
If you're asking what is the O.S. of sulfur and oxygen in the sulfate(IV) ion (SO3)2-, it is +4 (sulfur) and -2 (oxygen). Hence, the name sulfate(IV) ion.If you're asking what is the O.S. of sulfur and oxygen in the sulfate(VI) ion (SO4)2-, it is +6 (sulfur) and -2 (oxygen). Hence, the name sulfate(VI) ion.The "-ate", eg. nitrate, sulfate, phosphate, shows that it is a negative ion.The "-onium", eg. nitronium, hydroxonium, sulfonium, shows that it is a positive ion.The reason why oxygen has an O.S. of -2, is because it is more electronegative than every other element (except fluorine), and hence in order to achieve a stable octet, oxygen will 'bully' other atoms it is bonded with, by withdrawing the electrons in its covalent bonds, closer toward itself (ie. it's nucleus).Hence, for instance, in H2O (water), each of the 2 hydrogen atoms has an O.S. of +1, while the oxygen atom has an O.S. of -2. Because the electrons in the covalent bonds are actually more strongly attracted towards oxygen. This also (it's not a coincidence, it's actually all related, but most students, both 'O' and 'A' levels, usually don't appreciate its significance, the bigger picture) results in a permanent dipole between the oxygen and hydrogen, making water a polar molecule.But we're more concerned with O.S. in this discussion, and to understand it properly, you need to understand about electronegativity as well as formal charges. All 'A' level students are expected to know about electronegativity, but not all 'A' level students know about formal charges.
Originally posted by UltimaOnline:If you're asking what is the O.S. of sulfur and oxygen in the sulfate(IV) ion (SO3)2-, it is +4 (sulfur) and -2 (oxygen). Hence, the name sulfate(IV) ion.If you're asking what is the O.S. of sulfur and oxygen in the sulfate(VI) ion (SO4)2-, it is +6 (sulfur) and -2 (oxygen). Hence, the name sulfate(VI) ion.The "-ate", eg. nitrate, sulfate, phosphate, shows that it is a negative ion.The "-onium", eg. nitronium, hydroxonium, sulfonium, shows that it is a positive ion.The reason why oxygen has an O.S. of -2, is because it is more electronegative than every other element (except fluorine), and hence in order to achieve a stable octet, oxygen will 'bully' other atoms it is bonded with, by withdrawing the electrons in its covalent bonds, closer toward itself (ie. it's nucleus).Hence, for instance, in H2O (water), each of the 2 hydrogen atoms has an O.S. of +1, while the oxygen atom has an O.S. of -2. Because the electrons in the covalent bonds are actually more strongly attracted towards oxygen. This also (it's not a coincidence, it's actually all related, but most students, both 'O' and 'A' levels, usually don't appreciate its significance, the bigger picture) results in a permanent dipole between the oxygen and hydrogen, making water a polar molecule.But we're more concerned with O.S. in this discussion, and to understand it properly, you need to understand about electronegativity as well as formal charges. All 'A' level students are expected to know about electronegativity, but not all 'A' level students know about formal charges.
i "o" level student
Originally posted by SBS n SMRT:i "o" level student
Which means it's quite impossible for an 'O' level student to completely understand what Oxidation State (O.S.) is all about.
In which case, simply note the "rules" of O.S., which include the fact that you are not allowed to say "the O.S. of a polyatomic ion is..." (polyatomic ion means an ion containing 2 or more atoms) You are only allowed to say "the O.S. of (a particular element, eg. sulfur) in the (specified ion, eg. sulfate(VI) ion or SO4 2-) is (state the O.S., eg +6)."
Originally posted by UltimaOnline:
Which means it's quite impossible for an 'O' level student to completely understand what Oxidation State (O.S.) is all about.
In which case, simply note the "rules" of O.S., which include the fact that you are not allowed to say "the O.S. of a polyatomic ion is..." (polyatomic ion means an ion containing 2 or more atoms) You are only allowed to say "the O.S. of (a particular element, eg. sulfur) in the (specified ion, eg. sulfate(VI) ion or SO4 2-) is (state the O.S., eg +6)."
Okays..thanks...anyway for me now just care OS for redox reactions