## 6th Edition Problem 8.21

lizettelopez1F
Posts: 29
Joined: Fri Sep 28, 2018 12:19 am

### 6th Edition 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.

What is the general equation that needs to be used to find the final temperature of the water?

beckyolmedo1G
Posts: 34
Joined: Fri Sep 28, 2018 12:21 am

### Re: 6th Edition Problem 8.21

heat lost by the copper= -heat gained by the water
so, you use the equation (mass of copper)(Tfinal-TInitial of copper)(C)=-(mass of water)(Tfinal-Tinitial of water)(C). Then solve for Tfinal

KarlaArevalo2F
Posts: 67
Joined: Tue Nov 14, 2017 3:01 am
Been upvoted: 1 time

### Re: 6th Edition Problem 8.21

hi becky, how did you derive this equation?

Heesu_Kim_1F
Posts: 60
Joined: Fri Sep 28, 2018 12:18 am

### Re: 6th Edition Problem 8.21

Hi, this might help.
The idea comes from Qsystem+Qsurr=0.
Qsystem = -Qsurr, in which copper = system and water = surrounding.
Thus, heat lost by copper = -heat gained by water.
Then use the calorimetry equation q = m x Cp x delta T to solve.

Saman Andalib 1H
Posts: 73
Joined: Fri Sep 28, 2018 12:16 am

### Re: 6th Edition Problem 8.21

The general concept that is used here is heat lost by the copper= -heat gained by the water. In the formula, the only thing that is a little bit tricky is that you have to use (Tfinal-Tinitial) for the variable delta T, then use algebra to simplify the equation to solve for Tfinal.

Kobe_Wright
Posts: 83
Joined: Fri Sep 28, 2018 12:16 am

### Re: 6th Edition Problem 8.21

What would cp be in this equation?

Kobe_Wright
Posts: 83
Joined: Fri Sep 28, 2018 12:16 am

### Re: 6th Edition Problem 8.21

What would cp be in this equation?

Lynsea_Southwick_2K
Posts: 55
Joined: Fri Sep 28, 2018 12:25 am

### Re: 6th Edition Problem 8.21

cp would be different for copper and water. Cp copper = o.38 J/Celsius*g and cp water is 4.18 J/Celsius*g

Kobe_Wright wrote:What would cp be in this equation?

Chloe Likwong 2K
Posts: 70
Joined: Fri Sep 28, 2018 12:23 am

### Re: 6th Edition Problem 8.21

Kobe_Wright wrote:What would cp be in this equation?

If the substance is anything except water, the Cp is usually given in the question.