Friday
April 18, 2014

Homework Help: Chemistry

Posted by Lindsay on Monday, May 14, 2007 at 5:51pm.

This is sort of like the one I last posted, only it asks for the final temp. instead of energy...

What is the final temp. (in degrees C) after a 15.5 g piece of ice at 0 degrees C is placed into a styrofoam cup with 125.0 g of water initially at 72.0 degrees C? Assume no loss or gain of heat from the surroundings.

So I know that the molar enthalpy heat of fusion is 333 J/g, and the specific heat of water is 4.184 J/gK. Is this simply about rearranging the specific heat equation, or is it more than just that?

q to melt ice + q raise temp of water from zero to final T + heat lost by water at 72 = 0

(15.5 x 334 J/g*K) + 15.5*4.184*(Tf-Ti) + 125.0*4.184*(Tf-Ti) = 0

Tf is final T
Ti is initial T
Solve for Tf.

Ok so I see what you're saying. But honestly, I have no idea how to go about solving for Tf.

Can u give me a hint?

Perhaps the structure is confusing. I posted the equation. All that's left is doing the algebra.
(15.5 x 334) + [15.5 x 4.184 x (Tf -0)] + [125.0 x 4.184 x (Tf - 72)] = 0
There is only one unknown, Tf. Solve for Tf = T final

Ahh ok I see, I got it.

Thanks again for all of your help! I still have quite a few Chem questions I'm unsure about, but I think I'll call it good for tonight. :)

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