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Advanced Higher Chemistry Investigation help - Olive oil watch

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    I am carrying out experiments to find the peroxide value of olive oil at different temperatures (fridge, room, 40, 60 and 80 degrees celsius). I am using “Sainsbury’s mild olive oil”. It is composed of refined and virgin olive oils. I have outlined the procedure below:

    The oil was kept at the above temperatures for a week before the titrations. About 5g of olive oil was mixed with 30cm3 of a 3:2 (by volume) of glacial acetic acid and hexane in an ultrasonic water bath for 2 mins. Then about 0.5cm3 of saturated potassium iodide was added to the solution and swirled for 1 minute. Then 30cm3 of de-ionised water was added to the mixture. The mixture was titrated with 0.001mol l-1 sodium thiosulphate solution (rather than 0.01mol l-1 to give a larger titre) until the yellow colour of the iodide had almost disappeared. Then about 0.5cm3 of starch solution was added to act as indicator, and the titration was continued until the blue/black colour had disappeared. The final titre volume was recorded. A blank titration without the sample was also carried out.

    The questions I have are as follows:

    I am finding it difficult to get concordant titre volumes (within 0.1cm3). I am getting differences of more than 1 cm3. Should I be getting them? Could it be explained because there are two stages in the titration? Could the concentration of sodium thiosulphate affect the end-point? What PV values are expected at different temperatures?
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    I think this should be moved to 'Scottish Qualifications'.
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    I'm sorry, I'm new to this.
    I don't know how to move this thread or delete it.
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    (Original post by Double Trouble)
    I'm sorry, I'm new to this.
    I don't know how to move this thread or delete it.
    Hello New Person,

    Don't worry, someone will (hopefully) move it for you.
    • TSR Community Team
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    TSR Community Team
    Hi there,

    Out of curiosity, could I ask why you posted your question in this forum? Nothing wrong, but we seem to get a lot of non-Wiki related posts here (including this one) and am interested to find out what's the cause.

    Please do let me know
 
 
 
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