## Homework Problem 8.21

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

### Homework Problem 8.21

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

### Re: Homework Problem 8.21

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

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

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
Posts: 31
Joined: Fri Sep 29, 2017 7:05 am

### Re: Homework Problem 8.21

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
Posts: 75
Joined: Fri Sep 28, 2018 12:27 am

### Re: Homework Problem 8.21

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