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Unit 1 ppas 1+2 - HSN forum

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Unit 1 ppas 1+2


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#1 gary

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Posted 30 May 2005 - 12:57 AM

Hey can someone quickly explain the steps taken in both these experiments i always get the temperature and concentration ppas mixed up.

Thanks.

#2 gary

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Posted 30 May 2005 - 10:25 AM

help

#3 bigears1

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Posted 30 May 2005 - 10:26 AM

Not too sure to be honest, the best that i can do is give you this link, and you can open up the PPA's and take a look
http://www.hsn.uk.net/downloads/Hchem
hopefully somebody else will come and answer this properly

#4 gary

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Posted 30 May 2005 - 10:28 AM

thanks the unit 1 ppas are not there think it is against SQA regulations because they are used for LO3.

#5 YIC

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Posted 30 May 2005 - 11:50 AM

That is strange, the unit 2 and 3 ones are there.

PPA 1 (Concentration) is the reaction between potasium iodide and hydrogen peroxide, with the variable being the concentration of the iodide ions. Starch is used as an indicator and the reaction is timed until the mixture turns blue.

PPA 2 (temperature) is the reaction between oxalic acid and permanganate ions. The experiement is done at different temperatures and the reaction is timed until the purple mixture goes colourless. The experiement can't be done at room temperature because the reaction would be too slow and the colour change would be too gradual and hard to see. Also, the beaker has to be dry otherwise some solutions can become diluted and results can become inaccurate.

I actually downloaded the PPA sheets from this site a long time ago, and much of the stuff I got was from there.

#6 Ally

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Posted 30 May 2005 - 01:44 PM

Yeh, the site got contacted by the SQA (well LTScotland) and they were'nt happy with the unit 1 PPA's being up, so they were removed a couple of months back.

Bred posted some answers here though: http://www.hsn.uk.net/forum/index.php?showtopic=377#

#7 YIC

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Posted 30 May 2005 - 05:41 PM

Could someone tell me why the following substances are used in the first PPA (concentration)

1) Sulphuric acid
2) Sodium thiosulphate

thanks smile.gif

#8 YIC

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Posted 30 May 2005 - 07:57 PM

anyone. please? sweatingbullets.gif





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