AB , A_(2) and B_(2) are diatomic molecules, if the bond enthalpies of A_(2) , AB and B_(2) are in the ratio of 1:1:0.5 and the enthaly of formation of AB from A_(2) gives AO and DeltaH_(c)=-1200KJ mol^(-1) . Bond energy of (O=O) bond is 500KJ mol^(-1) . What is the bond enthalpy of (A-O) bond ?

AB , A_(2) and B_(2) are diatomic molecules, if the bond enthalpies of

1.	AB , A_(2) and B_(2) are diatomic molecules, if the bond enthalpies of A_(2) , AB and B_(2) are in the ratio of 1:1:0.5 and the enthaly of formation of AB from A_(2) gives AO and DeltaH_(c)=-1200KJ mol^(-1) . Bond energy of (O=O) bond is 500KJ mol^(-1) . What is the bond enthalpy of (A-O) bond ?
Answer» `400KJmol-1` `1650KJmol-1` `1200KJmol-1` `200KJmol-1` SOLUTION :Bond enthalpy `(BE)` of `A_(2)=x,AB=x` and `B_(2)=(x)/(2)` `(1)/(2)A_(2)+(1)/(2)B_(2)rarrAB-100KJ//mol^(-1)` ...(i) `(1)/(2)A_(2)+(1)/(2)O_(2)rarrAO-1200KJ//mol` (given) `A_(2)+O_(2)rarr2AO-2400KJ//mol` ...(ii) `O=Orarr500KJ//mol` From eq. (i) `(1)/(2)B.E._(A_(2))+(1)/(2)B.E._(B_(2))-B.E._(AB)=-100` `(1)/(2)x+(x)/(4)-x=-100` `-(x)/(4)=-100` `x=400(kJ)/(mol)` Now from eq (ii) `B.E._(A_2)+B.E._(O_2)-2B.E._(AO)=-2400` `x+(+500)-2B.E._(AO)=-2400` `400+500-2B.E._(AO)=-2400` `-B.E._(AO)=-3300` `B.E._(A-O)=1650(kJ)//(mol)`