a$.$ Calculate the heat of the reaction for production of silicon carbide, begmning and ending at $1700C.$:

$Si{O}_2+3C=$SiC$+2CO.$

THER.MO$(\text{'}$HE:USTRY AND THERMOPHYSICS

$95$

b$.$ Iron carbide decomposes as follows, forming crystals of pure iron and graphite:

$F{e}_{3}C=3Fe+C.$

Required: The heat of this reaction, per pound of iron, $($a$)$ when it occurs in solid cast iron at a temperature of $2000F.,$ and $(b)$ when it occurs in the production of artificial graphite at a temperature of $4000F.$

$105.$ Calculate the heat of the reaction

$A{l}_2{O}_3+3C=2Al+3CO,$

taking place in the Hall process at a temperature of $1000C.$ Although this temperature is below the melting point of $A{l}_2{O}_3,$ the alumina is actually in the liquid state, being dissolved in molten cryolite. Assume, therefore, that the heat content of the $A{l}_2{O}_3$ includes its heat of fusion.

$106.$ The reaction for reduction of zine from roasted zine ore is:

ZnO$+C=Zn+CO.$

Required: $1.$ The heat of this reaction as it takes place in the zine retort, beginning and ending at $1000C.$

$2.$ The heat required for the reaction, per kilogram of zine vapor produced, allowing for the fact that the zinc oxide and carbon are put into the retort cold $($assume $.$