Find initial temp. of alcohol when copper and aluminum are added

  • Thread starter nlingraham
  • Start date
  • #1
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*Messed up title, should have been find initial temp of copper*

Homework Statement



8.00 g of aluminum at 200 °C and 18.0 g of copper are dropped into 50.0 cm3 of ethyl alcohol at 15 °C. The temperature quickly comes to 26.0 °C. What was the initial temperature of the copper?

Density of ethyl alcohol = .789 g/ml

mass of ethyl alcohol = 39.45 g, .03495 kg

mass of copper = .018 kg

mass of aluminum = .008 kg

Tf = 299 K

Ti, alum = 473 K

Ti, eth = 288 K

c for aluminum = 900 J/kg*k

c for ethyl alcohol = 2400 J/kg*k

c for copper = 385 J/kg*k

Homework Equations



Qa + Qc + Qe = macaΔT + meceΔT + mcccΔT = 0

The Attempt at a Solution




Qa + Qc + Qe = macaΔT + meceΔT + mcccΔT = 0

=(.008)(900)(-174) + (.03945)(2400)(11) + (.018)(385)(299-Ti) = 0

Ti = 268.51 K or -4.5 °C

That's what I did, but it says not quite and tells to check for rounding errors. However, I didn't round anything until the very end, so I'm not quite sure where I went wrong. I also tried -4.494 but that was wrong too.
 

Answers and Replies

  • #2
TSny
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mass of ethyl alcohol = 39.45 g, .03495 kg
Could this be the error?
 
  • #3
16
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Well, I feel stupid now. thanks.
 
  • #4
TSny
Homework Helper
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No need to worry. We all make slips like that. Hope it works out now.
 

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