Homework Problem 8.21

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David Bui 1C
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Joined: Fri Sep 25, 2015 3:00 am

Homework Problem 8.21

Postby David Bui 1C » Mon Jan 11, 2016 10:57 pm

A piece of copper of mass 20.0 g at 100.0 C is placed in a vessel of negligible heat capacity but containing 50.7 g of water at 22.0 C. Calculate the final temperature of the water. Assume
that no energy is lost to the surroundings.

I am assuming that this has something to do with the equation q=nCmΔT. I may be wrong.

Cindy Chen_2I
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Joined: Wed Nov 18, 2015 3:00 am

Re: Homework Problem 8.21

Postby Cindy Chen_2I » Mon Jan 11, 2016 11:24 pm

should be something like this:
heat released = heat absorbed
20 (mass)*0.39 (specific heat of Cu) *(100-T) (change in temperature) = 50.7 (mass)* 1 (specific heat of H2O) *(T-22)(change in temperature)

Try to solve for T. I got 32.4 degree Celsius as the final temperature.

David Bui 1C
Posts: 17
Joined: Fri Sep 25, 2015 3:00 am

Re: Homework Problem 8.21

Postby David Bui 1C » Tue Jan 12, 2016 10:59 am

Cindy Chen_2I wrote:should be something like this:
heat released = heat absorbed
20 (mass)*0.39 (specific heat of Cu) *(100-T) (change in temperature) = 50.7 (mass)* 1 (specific heat of H2O) *(T-22)(change in temperature)

Try to solve for T. I got 32.4 degree Celsius as the final temperature.



Thanks you gave me the right way to solve it. But the final answer was 25 degrees Celcius.

Cindy Chen_2I
Posts: 43
Joined: Wed Nov 18, 2015 3:00 am

Re: Homework Problem 8.21

Postby Cindy Chen_2I » Sat Jan 16, 2016 9:44 pm

Oh haha sorry. It should be 20*0.39*(100-T) = 50.7*4.18*(T-22)
you get 24.8 degree for the answer.

Sorry again for the confusion.

KayleeMcCord1F
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Joined: Fri Sep 29, 2017 7:05 am

Re: Homework Problem 8.21

Postby KayleeMcCord1F » Sat Mar 17, 2018 3:58 pm

I think the equation goes (Tf-Ti) so for the Copper side it should be (T-100), because both the water and Copper should have the same final temperature at equilibrium. This will yield the 24.8 degrees C.

Edward Suarez 1I
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Joined: Fri Sep 28, 2018 12:27 am

Re: Homework Problem 8.21

Postby Edward Suarez 1I » Mon Feb 04, 2019 5:39 pm

KayleeMcCord1F wrote:I think the equation goes (Tf-Ti) so for the Copper side it should be (T-100), because both the water and Copper should have the same final temperature at equilibrium. This will yield the 24.8 degrees C.


i thought the same but every time i worked it out i always got 19. something... am i doing the math part wrong lol

Adrian C 1D
Posts: 60
Joined: Fri Sep 28, 2018 12:19 am

Re: Homework Problem 8.21

Postby Adrian C 1D » Fri Feb 08, 2019 7:02 pm

No it would actually be (100-Tf). This is due to the temperature of the copper being 100 degrees celsius, which would result in the change in temperature for the copper to be negative. This would result in a negative answer when (Tf -100) or (100-Tf) to make it easier in the equation.


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