# Equilibrium Question with water and ice

1. Apr 3, 2015

### Lisa Marie

1. The problem statement, all variables and given/known data
5.0 kg of ice at 0◦ is put into 3.0 kg of water at 20◦C. Assuming that they are isolated, that cH2O = 4186 J /kg K , and that L = 3.3 × 105 J/ kg how much ice is left when the system comes to equilibrium?

2. Relevant equations
Q= +/- mL
Q=mcΔT

3. The attempt at a solution
mLice+mcΔTwater=0
5(3.3×105)+3(T-293)(4186)=0
T=266.7K
This answer is clearly incorrect as it would give you a negative Celsius temperature. Also how would you find mass from this?

Any help would be much appreciated!

2. Apr 3, 2015

### TSny

If there is some ice left when the system comes to equilibrium, what is the final temperature of the system?

Why do you use 5 here? Does all of the ice melt?

3. Apr 3, 2015

### Lisa Marie

Ok I see so you have to use (5-mf) but then there are two unknowns....

4. Apr 3, 2015

### SammyS

Staff Emeritus

You answered regarding using (5 - mf) rather than using 5.

He also asked "If there is some ice left when the system comes to equilibrium, what is the final temperature of the system?"

So, what is the final temperature in that case?

5. Apr 3, 2015

### Lisa Marie

Um I'm not really sure because there is two unknowns... so I guess I need another equation?

6. Apr 3, 2015

### SammyS

Staff Emeritus
If the system reaches equilibrium and some ice remains along with the (liquid) water, what is the temperature?

7. Apr 6, 2015

### Halo CX

There will be only a single unknown. If at equilibrium ice is present with water, then think about the temperature of the ice.