This can be stated mathematically qbi qal2o3 the minus

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Unformatted text preview: lls, they can only exchange heat with one anot her. In other words, whatev er heat leaves the bis muth must enter the alumina. This can be stated mathematically: qBi = "qAl2O3 The minus sign tells us that the direction of heat flow in the alumina is opposite that of the bis muth (e.g., heat flowing out of the bis muth is flowing into the alumina.) This equality immediat ely tells us how to determine the final temperature of the system- sinc e it must be the same in the bis muth and the alumina: ! qBi = "qAl2O3 Tf 544 #n 600 Bi C Bi, l p dT " n Bi$H m + #n 544 Bi C Bi, s p %T f ( dT = "' # n Al2O3 C pAl2O3 ,sdT* ' * &298 ) A few comments: In writing the left-hand ex pression, we are making the assumption that the Bi will cool enough to pass through the melting point and solidify. Note that because we are passing from high to low ! mperature, we have a minus sign in f ront of the enthalpy of melting- we must remove te heat from t he sample to freez e it. To proceed, we ne...
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This document was uploaded on 12/21/2013.

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