Dismiss Notice
Join Physics Forums Today!
The friendliest, high quality science and math community on the planet! Everyone who loves science is here!

Homework Help: Latent heat of steam

  1. Feb 22, 2008 #1
    1. The problem statement, all variables and given/known data
    Ive been tasked with working out the Latent heat of steam
    the following are all my results and values used.

    Mass of the calorimeter and stirrer: 0.068Kg
    Thermal Capacity of the Calorimeter and Stirrer : 25.772 JK-1
    Mass of water and Calorimeter and stirrer: 0.145Kg
    Mass of water = 0.077
    Thermal capacity of water: 323.4
    Thermal capacity of calorimeter and water: 349.172
    Starting Temperature: 19.5 Degrees C
    Ending temperature 56 Degrees C
    Mass of calorimeter & water after passing steam 0.151Kg
    Mass of the condensed steam 0.006Kg
    Heat gained by the water: 12744.778
    Latent heat capacity of steam: 11635.978 Jkg

    2. Relevant equations
    The equations i had to use are
    Thermal Cap of Calorimeter and stirrer = weight x 379 (I cant read my tutors hand wrighting, but i think thats the thermal capacity of copper or along them lines, just know the value 379 to be correct, least I hope it to be)

    The Thermal Capacity of water I have as (Total weight - Weight before water added) * 4200

    For heat gained by water we where given the equation:
    (Thermal Capacity of Water + Thermal Capacity of the Calorimeter) * temprature rise (((From now on referd to as Ct)))

    The final equation (and the one I think might be wrong) is this for the calculation of the Latent heat capacity of steam
    Ct(T2-T1) - Ms Cw ( 100-T2) / Ms

    Ct ((see above))
    T2 56 Deg C
    T1 19.5 Deg C
    Ms = Mass of condenced steam (0.006 kg)
    and Cw Ive got down as 4186, I think this is ment to stand for the Thermal Capacity of Water, esp if Ct stands for the CT of water + Calorimeter. If im right then it should be 318.136 not 4186

    3. The attempt at a solution

    Well most of it ive done above. but i make the answer to be
    343.9(56-19.5)-0.006*4186(100-56) / 0.006

    geting me the answer of 11275.

    Ive been told that its ment to be 2256000 by my tutor but another said it should be 2256. There are a few 000 missing between the, but neather knew the units (yea, I know) so i looked around and I foud that its being said to be 2260J per Gram

    This is where im stuck.

    Ive just got no idear if ive done this wrong, if ive been told wrong values, so trying to deside if the result ive got is right or wrong is sending me crazy

    If anyone can clear this up for me that would be fantastic.

    and the final question would be. whats the equation to work out Molar latent heat capacity of steam.?

    Thanks very much

  2. jcsd
Share this great discussion with others via Reddit, Google+, Twitter, or Facebook

Can you offer guidance or do you also need help?
Draft saved Draft deleted