Please check my work energy required to raise temp by 10degthanks


    You want to heat 1 L of water by 10 ºC, and so you heat it with a mechanical egg beater that is powered by a 1 kg mass on a rope over a pulley. How far does the mass have to descend to supply enough work for heating the water?

    2. Relevant equations
    |work| = mg(x_f - x_0)
    C_P (liquid water) = 75.3JK^-1mol^1

    3. The attempt at a solution
    I first asked myself how much energy does it take to increase the temp of 1kg of water by 10degC.
    Heat capacity of water (above) is the energy required to heat 1 mol of water by 1deg.
    So I first determined how many moles of water i have:

    1L = 1kg = 1000g * (1mol/18.01g) = 55.5mol of liquid water

    Therefore 55.5mol *75.3JK^-1mol^1 = 4179.15J/K * 10K = 417915.0J

    So it requires 417915.0J to raise the temp of 1kg water by 10degC.

    This is the work required also because work is also in joules, --energy.

    Then i used the formula for mechanical work to determine the value for delta x.

    |work| = mg(x_f - x_0)

    417915.0J(1kJ/10000J) = 1kg(9.81m/s/s)(x_f) (i got ride of x_0 because I set scale so that x_0 = 0)

    x_f = 42.6m

    So the mass has to descend through 42.6m in order to heat 1kg of liquid water by 10 degC.

    Is this correct or if not please help..thanks alot. I also have some other questions about the problem but i dont want to ask until i know if my answer is correct...thank you again

    2. Relevant equations

    3. The attempt at a solution
  2. jcsd

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