Ch 8.1 Solving work


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Grace Han 2K
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Joined: Tue Nov 15, 2016 3:00 am

Ch 8.1 Solving work

Postby Grace Han 2K » Mon Jan 15, 2018 10:41 pm

In the textbook page 264, there's a self-test problem 8.1A and I keep getting a different answer than the answer provided.

Water expands when it freezes. How much work does 100. g of water do when it freezes at and pushes back the metal wall of a pipe that exerts an opposing pressure of 1070 atm? The densities of water and ice at are 1.00 and 0.92 , respectively.

My answer: -0.94 kJ

Does anyone know how to solve it? The textbook's answer is -0.86 kJ.

Abel Thomas 2C
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Re: Ch 8.1 Solving work

Postby Abel Thomas 2C » Tue Jan 16, 2018 12:47 am

I think the textbook's answer for this problem is not precise. If you don't round till the end, W should be -0.94 kJ, so you should be correct.

Sohini Halder 1G
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Re: Ch 8.1 Solving work

Postby Sohini Halder 1G » Tue Jan 16, 2018 12:18 pm

I got the same answer as you. For those who need help solving the problem, here is my work:

Volume of water as liquid:
100 g / (1g/cm^3) = 100 cm^3

Volume of water as solid:
100 g / (0.92g/cm^3) = 108.696 cm^3

Change in volume:
8.696 cm^3
Converted to Liters:
0.008696 L

External pressure:
1070 atm

w = -Pex(delta)V
w = -(1070 atm)(0.008696L)(101.325J/1Latm)
w = -940 J = -0.94 kJ


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