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Mass of N loss

~christina~
Gold Member
712
0
[SOLVED] Mass of N loss

1. Homework Statement
1.00kg block of Cu at 20C is dropped into a large vessel of liq Nitrogen at 77.3K. How many kg of Nitrogen boil away by the time the copper reaches 77.3K?
specific heat of Cu is 0.0920cal/g C. The latent heat of vaporization of Nitrogen is 48.0cal/g

2. Homework Equations
[tex]Q= mc\Delta T[/tex]
[tex]Q= \pm mL[/tex]
[tex] Q_{cold}= -Q_{hot} [/tex]
3. The Attempt at a Solution

I'm not sure how to do this problem but I know what equations are needed.
L= 48.0cal/g
[tex]M_{cu}= 1.00kg[/tex]
[tex]M_{N}= ? [/tex]
[tex]T_f= 77.3K= -195.85^oC [/tex]
[tex]T_i= 20^oC[/tex]

Do I just solve for mass of the Nitrogen after I equate the 2 energy equations together?
like this:
[tex]- M_{Cu}C_{Cu}\Delta T= M_{Nitrogen}L[/tex]


Help please.

Thank You
 
Last edited:

Answers and Replies

Kurdt
Staff Emeritus
Science Advisor
Gold Member
4,769
6
Yes you would solve for the mass of nitrogen since the energy from the copper will be the energy used to change the nitrogen from liquid to solid.
 
~christina~
Gold Member
712
0
Yes you would solve for the mass of nitrogen since the energy from the copper will be the energy used to change the nitrogen from liquid to solid.
Thanks alot Kurdt :smile:
 

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