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    Hello, I have a question: when using "q = m x c x delta't,' how do I know if the answer is positive or negative?

    I thought that it was always negative because the "delta't'" means there's a temperature increase and thus, heat is given out, but in the textbook (for one of the questions), the enthalpy change of neutralisation is positive

    Help? Please!
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    ▲T is the change of energy ie. temperature.
    A negative means that energy is released and a positive means that energy is taken from the environment (exothermic and endothermic).
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    (Original post by notepad)
    Hello, I have a question: when using "q = m x c x delta't,' how do I know if the answer is positive or negative?

    I thought that it was always negative because the "delta't'" means there's a temperature increase and thus, heat is given out, but in the textbook (for one of the questions), the enthalpy change of neutralisation is positive

    Help? Please!
    It really depends on whether the given reaction is Endothermic or Exothermic.. and you have to judge from there whether to include the negative or positive sign depending on the reaction type. If the overal reaction is exothermic, then at the end, you must include the "-" negative sign of your answer..
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    (Original post by Nashy19)
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    (Original post by Haz Shah)
    It really depends on whether the given reaction is Endothermic or Exothermic.. and you have to judge from there whether to include the negative or positive sign depending on the reaction type. If the overal reaction is exothermic, then at the end, you must include the "-" negative sign of your answer..
    My question is, how do I know if it is endothermic or exothermic? Will it tell me in the question? Or will I just have to figure it out for myself (if so, how?)/guess =S
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    If there is a temperature decrease in the surroundings, it means it's Endothermic, meaning that energy has been gained.
    If there is a temperature increase in the surrounds, it means it's Exothermic, meaning that energy has been lost.

    If the temperature moves from 37 to 25, then its a Endothermic, if it moved in the other direction it means its Exothermic.

    Combustion is always exothermic btw.
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    Thanks guys
 
 
 
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