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Chemistry Individual Investigation

Starter Page 1

The kinetics of the reaction between hydrogen peroxideand potassium iodide

The arcourt ! "ssen# reaction

Hydrogen peroxide reacts with iodide ions in acid solution to produce iodine andwater.

H2O2 + 2I- + 2H+ I2 + 2H2O

You can measure the rate of reaction by adding a nown amount of sodium

thiosulphate solution and some starch indicator to the mixture and measuring thetimeit taes for the solution to turn blue.

Your first tas is to carry out some preliminary experiments to wor out what aresuitable amounts of solutions to mix together

$e%uirements

potassium iodide solution! ".#"" moldm-$

sulfuric acid! #.""" moldm-$

sodium thiosulfate solution! ".""% moldm-$

hydrogen peroxide solution! # &olume 'which is about #.""" moldm-$(

starch solution

&etting started

)et up some burettes for your solutions. Into a small beaer measure #" cm $ ofsulphuric acid! * cm$of sodium thiosulfate! 2% cm$of potassium iodide #cm$of starchsolution and cm$of water. ,un #" cm$of hydrogen peroxide into a conical flas.dd the contents of the beaer to the flas and start a stop watch. )top the watch

when the mixture turns blue and note the time taen.

re the &olumes of solutions suitable or do you need to modify them

/hen you are satisfied that you ha&e appropriate solutions you can change theconcentration of hydrogen peroxide carefully and accurately to achie&e a sufficientnumber of results that will allow you to draw an accurate graph which you can use tofind the order of reaction with respect to hydrogen peroxide.

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