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  • Message 1. 

    Posted by U15235539 (U15235539) on Monday, 27th May 2013

    really don't understand how to do 2011,question 14a

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  • Message 2

    , in reply to message 1.

    Posted by MissChemTeacher_Bitesize (U15172316) on Monday, 27th May 2013

    Hey!
    These predict questions can be quite tricky. You've got to try and look for a trend in the data. The enthaply of combustion increases as the number of carbon atoms in your fuel increases. They're looking for you to use the table to predict the enthalpy of combustion for next fuel in the series.

    The difference in values between methanol and ethanol is -640kJ

    The difference in values between ethanol and propan-1-ol is -653kJ

    I estimated that the next fuel in the series would increase the enthalpy of combustion by a similar number. I added -666kJ to the value given for propan-1-ol. I got that value by looking at the previous differences and adding another -13kJ on.

    I added that onto the -2020kJ to get a value for butan-1-ol. That gave me -2686kJ

    The marking scheme states that any answer within range -2640 to -2690 is acceptable.

    Hope that helps you out.

    Cheers Miss_Chem smiley - cool

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  • Message 3

    , in reply to message 2.

    Posted by U15235539 (U15235539) on Thursday, 30th May 2013

    yes thank you

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