1. Not finding help here? Sign up for a free 30min tutor trial with Chegg Tutors
    Dismiss Notice
Dismiss Notice
Join Physics Forums Today!
The friendliest, high quality science and math community on the planet! Everyone who loves science is here!

How much heat will be lost

  1. Jul 28, 2010 #1
    Question #1
    1. The problem statement, all variables and given/known data
    How much heat will be lost when 120 g of steam at 100°C is condensed to water at 80°C?


    2. Relevant equations

    Q = mc∆t
    Q = m LV

    3. The attempt at a solution

    Q = mc∆t
    Q = 0.12 x 4186 x (80 – 100)
    Q = 10046.4 J
    Q = m LV
    Q = 0.12 x (- 2.3 x 106)
    Q = 276000 J
    = 10046.4 + 276000 = 286046.4
    = -2.9 x 105 J

    Is the latent heat of condensation negative to that of vaporization?

    Question #2
    1. The problem statement, all variables and given/known data
    If 20 g of ice at 0° is added to 180 g of water at 22°C, what will the final temperature of the water be?

    2. Relevant equations
    Q = mc∆t

    3. The attempt at a solution
    mc∆t = mc∆t
    0.02 x 2050 (0-T) = 0.18 x 4186 (T-22)
    -41T = 753.48T - 16576.56
    -794.48T = -16576.56
    -794.48T/-794.48 = -16576.56/-794.48
    T = 20.86

    For this question, is the latent heat of fusion needed?
     
    Last edited: Jul 28, 2010
  2. jcsd
  3. Jul 28, 2010 #2

    Mapes

    User Avatar
    Science Advisor
    Homework Helper
    Gold Member

    Yes, it has the opposite sign, as energy is required for vaporization but released by condensation. You calculations look good.
     
  4. Jul 28, 2010 #3
    Thanks for the reply! I'd like someone to confirm the second question too. Thanks in advance.
     
  5. Jul 28, 2010 #4
    :O no one?
     
  6. Jul 28, 2010 #5

    rl.bhat

    User Avatar
    Homework Helper

    Heat lost by water = mwc(22 - t)

    Heat gained by the ice = miL + mic(t-0) where L is the latent heat of fusion of ice.

    Now solve for t.
     
  7. Jul 29, 2010 #6
    Many thanks for your reply!
     
Know someone interested in this topic? Share this thread via Reddit, Google+, Twitter, or Facebook




Similar Discussions: How much heat will be lost
  1. How much heat needed? (Replies: 6)

Loading...