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vdeity
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Homework Statement
A certain storm cloud has a potential of 1.50 x 10^8 V relative to a tree. If, during a lightning storm, 50.0 C of charge is transferred through this potential difference and 1.00% of the energy is absorbed by the tree, how much sap in the tree can be boiled away? Model the sap as water initially at 26.0°C. Water has a specific heat of 4186 J/(kg·C°), a boiling point of 100°C, and a latent heat of vaporization of 2.26 x 10^6 J/kg.
Homework Equations
I'm actually kinda iffy on all the equations, but I got several answers that WebAssign told me was wrong...
The Attempt at a Solution
Energy gain of 50.0 C of charge accelerated through potential difference of (1.50 x 10^8 V) is (50.0 C)(1.50 x 10^8 V) = 7.5 x 10^9 J.
To vaporize 1 kilogram of sap requires mcΔT = (1 kg)(4186 J/kg K)(100 - 26 degrees C) = 3.098 x 10^(5) J to heat to 100 degrees C
An additional 2.26 x 10^6 J for the state change from liquid to gas, for a total required energy of 3.098 x 10^(5) + 2.26 x 10^6 = 2.57 x 10^6 J.
The total energy absorbed is 1% of 7.5 x 10^9 = 7.5 x 10^7 J, and at 2.57 x 10^6 J per kg needed, we are able to vaporize:
(7.5 x 10^7 J)/(2.57 x 10^6 J/kg) = 29.19 kg of sap.
WebAssign says it's wrong.
Please tell me where I went wrong.
It isn't due for a few days, I just wanted to get this assignment out of the way... Last question.
Thanks!