F3 Physic Latent Heat Homework pls help

[匿名]

2008-03-14 8:22 am

1. A heating coil takes 115 s to heat 0.1 kg of a liquid
from 20 c to its boiling pt 80 c. It needs a futher 340 s
to boil away 0.04 kg of the liquid.
If the specific heat capacity of the liquid is 2300 J/(kg c)
find the liquid 's specific latent heat of vaporization.
(No need to find the power of the power of the heating coil. just consider the ratio of the times used in two processes)

2. After some steam at 100 c is passes through blocks
of ice at 0 c, 40 g of water is collected . Find the mass
of the steam introduced
(hint : think about the temp of the collected water first)

pls help
very urgent!!!

THX

回答 (1)

STEVIE-G™

2008-03-14 10:40 pm

✔ 最佳答案

1. Let the power of the heating coil be P W and the liquid 's specific latent heat of vaporization be xJkg-1
A heating coil takes 115 s to heat 0.1 kg of a liquid
from 20 c to its boiling pt 80 c.
by E=Pt
(80-20)(2300)(0.1)=P(115)
P=120W
It needs a futher 340 s to boil away 0.04 kg of the liquid.
E=mlv
0.04(x)=(120)(340)
x=1.2*106Jkg-1
2.
In order to change the maximum ice into the water form , the temperature of the produced water must be at the minimum , i.e. 0oC
Let the mass of the steam introduced be m kg
The energy lost of the stream=The energy absorbed of the ice
m(2.26*106)+m(4200)(100-0)=(0.04)(3.34*105)
m(2.26*106+4200*100)=(0.04)(3.34*105)
m=0.005kg

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