Question #f4c22

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Answer 1 · 2016-08-20T07:20:29

Given

$C(gr)+O_2(g)->CO_2(g),DeltaH_1^@=-393.5" kJmol"^-1....(1)$

$CO+1/2O_2(g)->CO_2(g),DeltaH_2^@=-283.0" kJmol"^-1...(2)$

$CO+Cl_2(g)->COCl_2(g),DeltaH_3^@=-108.0" kJmol"^-1...(3)$

$"We are to determine "DeltaH_f^@" of " COCl_2(g)" for the reaction:"$

$C(gr)+1/2O_2(g)+Cl_2(g)->COCl_2(g),DeltaH_f^@=?$

It is obvious that adding(1) and (3) ,then subtracting (2) we can easily get $DeltaH_f^@$ of the reaction.

So

$DeltaH_f^@=DeltaH_1^@+DeltaH_3^@-DeltaH_2^@$

$DeltaH_f^@=(-393.5-108.0-(-283.0))" kJmol"^-1$

$=-218.5kJ"mol"^-1$