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VCE Stuff => VCE Science => VCE Mathematics/Science/Technology => VCE Subjects + Help => VCE Chemistry => Topic started by: Ematuro on February 26, 2011, 09:46:19 am

Title: Need some help with writing this redox equation.
Post by: Ematuro on February 26, 2011, 09:46:19 am: A manganese ore was analysed by titration with a freshly prepared acidified iron(II) sulfate solution.
The manganese was first oxidised to permanganate ion (MnO4−). The permanganate obtained from a 0.269 g sample of ore required a titre of 22.41 mL of 0.500 M FeSO4 solution to reach the endpoint.

How would you go about writing an equation for this?
I began with Mn --> MnO₄^-

But the answer does it the other way round. I dont get why? I mean in the equation it says permanganate obtained FROM a 0.269g sample of ore. So how come in the solutions they put it the other way round? Or did I misinterpret something?
Title: Re: Need some help with writing this redox equation.
Post by: huaxiadragon on February 26, 2011, 11:00:58 am: Well the Mn --> MnO4 is the first part of the solution.

The second part is where $MnO_{4}^{-}_{(aq)} + Fe^{2+}_{(aq)} + 8H^{+}_{(aq)} \xrightarrow ~Mn^{2+}_{(aq)} +4H_{2}O + 5Fe^{3+}_{(aq)}$

The permanganate reacts with Iron to change colour and form the Manganese ions.

P.S OMG I just learnt how to write equations in forum!
Title: Re: Need some help with writing this redox equation.
Post by: huaxiadragon on February 26, 2011, 11:02:29 am: Quote from: Ematuro on February 26, 2011, 09:46:19 am
But the answer does it the other way round. I dont get why? I mean in the equation it says permanganate obtained FROM a 0.269g sample of ore. So how come in the solutions they put it the other way round? Or did I misinterpret something?

You didn't misinterpret. But the titration actually occurs with the permanagate. Think of obtaining permanganate from the ore as a process BEFORE the titration is conducted.
Title: Re: Need some help with writing this redox equation.
Post by: Ematuro on February 26, 2011, 11:44:44 am: OH! I get it now thanks! I guess I didn't fully read the question properly after all
Title: Re: Need some help with writing this redox equation.
Post by: pi on February 26, 2011, 11:47:34 am: This sounds a lot like the steel wool prac...