Ethyl alcohol has a boiling point of 78.0°C, a freezing point of -114°C, a heat of vaporization of 879 kJ/kg, a heat of fusion of 109 kJ/kg, and specific heat of 2.43 kJ/(kg · K). How much energy must be removed from 0.584 kg of ethyl alcohol that is initially a gas at 78.0°C so that it becomes a solid at -144°C?(adsbygoogle = window.adsbygoogle || []).push({});

I know start out by finding the heat removed at the phase change.

Q_{1}= L_{v}m

= 879(0.584)

= 513.336 kJ

Then the heat involved to cool the liquid to −114°C...

Q_{2}= cmΔT

= 2.43(0.584)(78− - 114)

= 272.471 kJ

Then the phase change at −114°C...

Q_{3}= L_{f}m

= 109(0.584)

= 63.656 kJ

Adding them all together to get the total heat...

Q1 + Q2 + Q3 = 513.336 + 272.471 + 63.656 = 849.463 kJ

But webassign won't take my answer. What did I do wrong?

Please help. Thanks.

Edit: I figured out what I did wrong. Didn't pay attention to the final temperature. Got it right this time. :)

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# Homework Help: Total heat removed from phase change

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