Calculating heat of fusion?

Question

Hi there,
I'm struggling with the following question;
You take 196.5 g of a solid at 30.0oC and let it melt in 400. g of water. The water temperature decreases from 85.1oC to 30.0oC. Calculate the heat of fusion of this solid. Ignore significant figures for this problem.

Any walk through would be greatly appreciated. Thanks!

Superfly · Accepted Answer

Piece of cake.

So 400g of water drop from 85.1C to 30C give out heat of 400*(85.1-30)*4.186 J/g.C = 92259.4 Joule.

Assume all of those solid melted, then the heat of fusion of that solid is: 92259.4 Joule/196.5 g = 469.514 Joule/g or 470 joule/gram 

SuperFly

Anonymous · Answer

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RE:
Calculating heat of fusion?
Hi there,
I'm struggling with the following question;
You take 196.5 g of a solid at 30.0oC and let it melt in 400. g of water. The water temperature decreases from 85.1oC to 30.0oC. Calculate the heat of fusion of this solid. Ignore significant figures for this problem.

Any walk through would...

Norrie · Answer

Heat Lost by the water = 400g x 4.18J/g/°C x 55.1°C ΔT.
= 92,127 Joules. (Sensible heat)
Heat gained by solid = 196.5g x LHf.
Heat of fusion = 92,127J / 196.5g = 468.8 J/g (Latent heat).

Calculating heat of fusion?

3 Answers