a$.$ Given the following heats of formation $($from the tables, Chap. XXV$)$:

$(A{g}_{2}O,N_2{O}_5)=-46,100$

$(Ag,N_2,O_3)=-29,400.$

$(N_2,O_5)=+600.$

Required: The heat of oxidation of silver to $A{g}_{2}O,$ per kilogram of silver.

$b.$ Given the following heats of formation $(-H)$ :

MnO from $Mn$ and O: $1,757$ lb$.-$cal. per pound of $Mn.$

$S{O}_3$ from $S$ and $3$O: $2,930$ lb$.-$cal. per pound of $S.$

$MnS{O}_4$ from $Mn,S,$ and $40$: $1,664$ lb$.-$cal. per pound of $MnS{O}_4.$

Required: The molal heat of formation of $MnS{O}_4$ from MnO and $S{O}_3.$