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Problem 8 Hall Heroult cell
Calculate the heat of the reaction taking place in the Hall-Heroult cell at a temperature of 1000oc
Although this temperature is below the melting point  the alumina is actually dissolved in molten cryolite. Assume, therefore that heat content of the includes its heat of fusion. Heat of fusion of and Al is 1046.5 and  S respectively. Melting point of Al is  .
Components |
 (J/g.mol)
|
Cp (J/g.mol K) |
Al2O3 |
-380000 |
106.608 + 17.782 x10-3T-28.535x105T-2 |
C |
---------- |
17.154+4.268x10-3T-8.786x105T-2 |
Al(s) |
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-----------
|
20.669+12.385x10-3T
31.798 |
Al(l) |
CO |
-26840 |
28.409 + 4.1 x10-3T – 0.460 x 105T - 2 |
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The above problem has a relevance in electrolytic reduction of to produce Al. Hall- Heroult cell is widely used to produce aluminum.
Heat of reaction  .
Problem 9: Heat of Formation
Will heat of formation be different when a compound forms A) From two different compounds and (b) when if forms from pure elements.
Answer; Heat of formation will be different. For example Heal of formation of  when formed from elements and O
Heat of formation is  kcal when  forms from  and 
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