Unit 1 ppas 1+2
Posted 30 May 2005 - 12:57 AM
Posted 30 May 2005 - 10:28 AM
Posted 30 May 2005 - 11:50 AM
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.
Posted 30 May 2005 - 01:44 PM
Bred posted some answers here though: http://www.hsn.uk.net/forum/index.php?showtopic=377#
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Posted 30 May 2005 - 05:41 PM
1) Sulphuric acid
2) Sodium thiosulphate
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