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    So i was doing a past paper unit 5 aqa jun 13 and a Q=mcdeltaT question completely threw me off

    "A solution is formed when 5.00 g of potassium chloride are dissolved in 20.0 g of water.The initial temperature of the water is 298 K.Calculate the final temperature of the solution.In your calculation, assume that only the 20.0 g of water changes in temperature andthat the specific heat capacity of water is 4.18 J K^–1 g^–1"

    It was also previously given in the Q stem that the detaH solution of KCL is 17.2

    to obtain the corrrect answer, it was necessary to realise that the "heat absorbed" i.e. 'q' in q=mcdeltaT, can be obtained by multiplying the deltaH solution of KCL by the number of moles of KCL (5/mr)

    i competely and utterly do not understand why

    any help much appreciated. thanks
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    (Original post by hi-zen-berg)
    So i was doing a past paper unit 5 aqa jun 13 and a Q=mcdeltaT question completely threw me off

    "A solution is formed when 5.00 g of potassium chloride are dissolved in 20.0 g of water.The initial temperature of the water is 298 K.Calculate the final temperature of the solution.In your calculation, assume that only the 20.0 g of water changes in temperature andthat the specific heat capacity of water is 4.18 J K^–1 g^–1"

    It was also previously given in the Q stem that the detaH solution of KCL is 17.2

    to obtain the corrrect answer, it was necessary to realise that the "heat absorbed" i.e. 'q' in q=mcdeltaT, can be obtained by multiplying the deltaH solution of KCL by the number of moles of KCL (5/mr)

    i competely and utterly do not understand why

    any help much appreciated. thanks
    The energy per mol is obtained by dividing the energy change by the number of moles dissolved.
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    Hi hi-zen-berg

    I find it hard to answer these questions by typing so please see the attached picture. It is x by moles because it is a rearrangement of the equation charco pointed out above.

    I hope this helps!

    Alex
    Name:  WP_20160415_14_00_59_Rich (2).jpg
Views: 326
Size:  430.2 KB
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    (Original post by ajsullivan)
    Hi hi-zen-berg

    I find it hard to answer these questions by typing so please see the attached picture. It is x by moles because it is a rearrangement of the equation charco pointed out above.

    I hope this helps!

    Alex
    Name:  WP_20160415_14_00_59_Rich (2).jpg
Views: 326
Size:  430.2 KB
    YOU COMPLETE AND UTTER LEGEND!
    this reallly really helped me visualize the Q and honed in on what i didnt get

    thank you so, so much ajsullivan i hope you and your entire bloodline are forever blessed <3
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    (Original post by hi-zen-berg)
    YOU COMPLETE AND UTTER LEGEND!
    this reallly really helped me visualize the Q and honed in on what i didn't get

    thank you so, so much ajsullivan i hope you and your entire bloodline are forever blessed <3
    Wow that was a very nice thing to say!

    You are very welcome - best of luck

    Alex
 
 
 
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