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  1. #1
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    reaction 2

    1.05 g MgO is added to 110.5ml HCL with an initial temperature of 21.5 degrees Celsius and a final temperature of 34.5 degrees Celsius. calculate the KJ of energy released for the reaction. assume that 4.18 J of energy is required to change the temperature of one mL of solution to one Celsius degree.

    i am assuming we must use q=mcdeltat, although i keep getting stuck
    Last edited by william; February 14th 2010 at 05:01 PM.
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  2. #2
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    Quote Originally Posted by william View Post
    1.05 g MgO is added to 110.5ml HCL with an initial temperature of 21.5 degrees Celsius and a final temperature of 34.5 degrees Celsius. calculate the KJ of energy released for the reaction. assume that 4.18 J of energy is required to change the temperature of one mL of solution to one Celsius degree.

    i am assuming we must use q=mcdeltat, although i keep getting stuck
    1. From c=4.18\ \frac{kJ}{kg \cdot K} it seems that you are refering to water.

    2. You have to convert the measurements into kg:

    1.05 g = 0.00105 kg
    110.5 ml HCl (nearly water!) = 0.1105 kg
    difference of temperature (measured in Kelvin) 34.5C - 21.5C = 13 K

    3. Now use the mentioned formula to calculate the energy:

    Q = m \cdot c \cdot \Delta t

    That means:

    Q = 0.11155\ kg \cdot 4.18\ \frac{kJ}{kg \cdot K} \cdot 13\ K
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