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AS - Chem Q on q=mc[delta]t watch

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    q=mc[delta]t

    ...what units is q in? My textbook says kJ, but the answers to my exam papers seem to be taking those units as J.

    I'm so confuuuuuuuuuuuused.

    :mad:
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    It depends what units u are given for c.
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    (Original post by zombie)
    q=mc[delta]t

    ...what units is q in? My textbook says kJ, but the answers to my exam papers seem to be taking those units as J.

    I'm so confuuuuuuuuuuuused.

    :mad:
    Well 1 kJ = 1000 J.
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    (Original post by Nylex)
    Well 1 kJ = 1000 J.
    Usually for AS chem take it to be J then convert it to an enthalpy.
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    Joules is the correct answer because the specific heat capacity of water is measured in joules remember. You then divide by 1000 to get it in Kj or Kj mol-1 as most questions will ask.
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    specific heat capacity of water is usually in kJ per K per kg. ( as in it takes 4.12 kJ to heat one kg of water by one K) This means that the answer is in kJ. That's why u have to convert the mass into kg.
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    (Original post by Happyelf)
    specific heat capacity of water is usually in kJ per K per kg. ( as in it takes 4.12 kJ to heat one kg of water by one K) This means that the answer is in kJ. That's why u have to convert the mass into kg.
    No no no!!!

    Specific heat capacity of water:

    c=4.18 J g-1 K-1. This is the STANDARD UNIT

    Learn that right!!
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    (Original post by vinny2256)
    No no no!!!

    Specific heat capacity of water:

    c=4.18 J g-1 K-1. This is the STANDARD UNIT

    Learn that right!!
    J g-1 K-1 is the same as kJ kg-1 K-1

    ...i do believe...try it with some figures
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    (Original post by Happyelf)
    J g-1 K-1 is the same as kJ kg-1 K-1

    ...i do believe...try it with some figures

    Kj Kg-1 K-1 is NOT THE STANDARD UNIT!!!! Read what im saying!!
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    that's what i have written in my module book so i'm going with that....and it is the same anyway so it doesn't matter...and in the exam it doesn't matter which units u use unless it asks u for specific units.
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    (Original post by vinny2256)
    Kj Kg-1 K-1 is NOT THE STANDARD UNIT!!!! Read what im saying!!
    They are exactly the same. By the way, the standard unit is actually J kg^-1 K^-1 because a gram is not an SI unit. Chemists make is easier because they do mole calculations in grams as well. So the actual specific heat capacity of water is around 4.2^10*3 J kg^-1 K^-1
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    (Original post by mik1a)
    They are exactly the same. By the way, the standard unit is actually J kg^-1 K^-1 because a gram is not an SI unit. Chemists make is easier because they do mole calculations in grams as well. So the actual specific heat capacity of water is around 4.2^10*3 J kg^-1 K^-1
    Yes, read what mik1a is saying!
    Anyway, I think it is given if it is needed for any calculations (on CCEA anyway.)
 
 
 
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