- #1

maxim07

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- Homework Statement
- In an experiment to measure the specific latent heat of fusion of ice, 20g of crushed ice is added to a beaker of water of mass 160g (not including mass of beaker) at temperature 30°C. The final steady temperature of the water and ice mixture is found to be 20°C.

Take c to be 4.2 Jg^-1°C^-1

a) calculate the specific latent heat of fusion of ice in J/g

b) if 3g of the ice has already melted before it is added to the beaker, show how this changes the value for the latent heat of fusion.

I can do (a) but I know that the value for the latent heat of fusion in (b) should be smaller as less energy is needed to melt the ice, as some has turned into water. But the result I get for b is larger than for a. Is it correct?

- Relevant Equations
- Energy transferred from water = energy to melt ice + energy to raise temperature of ice that is now water

Ew = EL + Ei

a)

E

m

160 x 4.2 x (30 - 20) = 20L + (20 x 4.2 x 20)

L = (6720 - 1680)/20

= 252 J/g

b)

accounting for 3 gram of melted ice

160 x 4.2 x (30 - 20) = (20 - 3) + (20 x 4.2 x 20)

L = (6720 - 1680)/17

= 296 J/g

E

_{w}= E_{L}+ E_{i}m

_{w}c(T_{2}-T_{1}) = m_{i}L + m_{i}c(T_{2}-0)160 x 4.2 x (30 - 20) = 20L + (20 x 4.2 x 20)

L = (6720 - 1680)/20

= 252 J/g

b)

accounting for 3 gram of melted ice

160 x 4.2 x (30 - 20) = (20 - 3) + (20 x 4.2 x 20)

L = (6720 - 1680)/17

= 296 J/g