[Catalist] One for the Chemists

Fri Mar 4 15:57:05 AEDT 2016

----- Original Message -----
From: catalist at lists.stawa.net
To:"catalist at lists.stawa.net" 
Cc:
Sent:Fri, 4 Mar 2016 03:56:05 +0000
Subject:Re: [Catalist] One for the Chemists

	Hi All, to clarify you are correct that redox titrations are not in
the syllabus I was using the titration not for redox calculations,
but rather as a test of titration procedure, correct use of equipment,
calculation of moles and concentrations etc. 

	Thanks,

	Andrew 

		 Andrew Bland

		Teacher

		T:  +61 8 9752 5252

		F:  +61 8 9752 5299

		E:  abl at gmas.wa.edu.au [1]

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	FROM: Catalist [mailto:catalist-bounces at lists.stawa.net] ON BEHALF OF
Ann Moseley
SENT: Friday, 4 March 2016 11:47 AM
TO: catalist at lists.stawa.net
SUBJECT: Re: [Catalist] One for the Chemists

	I thought the same! I couldn't see redox titrations anywhere?!

	On 4 March 2016 at 11:32, de la Haye, Maya  wrote:

	Correct me if I am wrong but I thought redox titrations were out of
the new curriculum? 

	Maya 

 Sent from my iPhone

 On 3 Mar 2016, at 4:31 PM, Andrew Bland  wrote:

	Hi all, please check if you agree with this model answer, from a
validation after a redox titration, permanganate + hydrogen peroxide.
Thanks, Andrew. 

	Q: If insufficient acid is added in step 9, some of the permanganate
ions will react to form MnO2 instead of Mn2+. The equation for this
reaction is:

2 MnO4- + 3H2O2 + 2H+  à 2MnO2 + 4H2O +3O2

	The original equation is: 

	                             2MnO4- +
5H2O2 + 6H+à 5O2 + 2Mn2+ +8 H2O

	a. How would this affect the volume of KMnO4 used to reach the end
point? (Would it be more or less). Explain why. 

	A: In the original reaction, 2 mol of MnO4- will react with 5 mol of
H2O2. In the new reaction, 2 mol of MnO4- will react with 3 mol of
H2O2, meaning that more MnO4- would be required to react with the same
amount of H2O2 to reach the end point. 

	The result would be that the concentration of H2O2 would be over
estimated.

	Andrew Bland

	Teacher

	T:  +61 8 9752 5252

	F:  +61 8 9752 5299

	E:  abl at gmas.wa.edu.au [5]

	W: www.gmas.wa.edu.au [6] 

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