Calorimeter Problem: Final Temp of Water & Ice Mixture

[kill00]

Homework Statement

A 200.0 g aluminum calorimeter holds 300g of water at 75 C. 20 g of ice at 0 C are added to the water. What is the final temperature of the mixture?

Homework Equations

Use Lf= 33.5 x 10⁴
Cal= 900 J/kg C

The answer is 66.5 C

The Attempt at a Solution

Don't know where to start.

 

[kill00]

Well, this is what i came to:

Find the heat lost by the water, if it is cooled to 0 C:
(.3)(4186)(75) = 94185

Calculate the heat needed to melt the ice:
(.02)(33.5e4) = 6700Q left:
( 94185 - 6700) = 87485

Final temp = 87485 / ( .32)(4186) = 65.3 C

The answer is 66.5 C. I don't know what to do with the aluminum

 

[kill00]

Woohoo I think I got it:

QAL = (.2)(900)(65.3-75) = 1746

Final temp = (1746 + 87485) / (.32*4186) = 66.6 C