Hess's law ofheat of summatiion is based on law of conservation of energy. It has found significance in deriving heats of many reactions which either do not take place or if take place, than other side reactions also accompany it. For example heat of reaction for C+(1)/(2)O_(2) rarr CO can not be studied directly as it occurs with simultaneous reaction of oxidation of CO to CO_(2) . Bond energy is referred as heat enthalpy when a bond is broken to produce isolated gaseous atoms. In case of breaking up of bonds between unlike atoms e.g., C-H bond in CH_(4) , bond energy is referred as avarage bond energy as four C-H bonds are broken up. If C+(1)/(2)O_(2(g)) rarr CO_((g)), DeltaH =-110kJ C+H_(2)O_((g))rarrCO_((g))+H_(2(g)), DeltaH=132kJ The mole composition of mixture of steam and O_(2) and steam on being passed over coke at 1273K so that temperature remains constant is :

Hess's law ofheat of summatiion is based on law of conservation of ene

1.	Hess's law ofheat of summatiion is based on law of conservation of energy. It has found significance in deriving heats of many reactions which either do not take place or if take place, than other side reactions also accompany it. For example heat of reaction for C+(1)/(2)O_(2) rarr CO can not be studied directly as it occurs with simultaneous reaction of oxidation of CO to CO_(2) . Bond energy is referred as heat enthalpy when a bond is broken to produce isolated gaseous atoms. In case of breaking up of bonds between unlike atoms e.g., C-H bond in CH_(4) , bond energy is referred as avarage bond energy as four C-H bonds are broken up. If C+(1)/(2)O_(2(g)) rarr CO_((g)), DeltaH =-110kJ C+H_(2)O_((g))rarrCO_((g))+H_(2(g)), DeltaH=132kJ The mole composition of mixture of steam and O_(2) and steam on being passed over coke at 1273K so that temperature remains constant is :
Answer» `0.6:1` `1.67:1` `0.3:1` `0.4:1` Solution :Let `n_(1)` MOLE of `O_(2)` and `n_(2)` mole of `H_(2)O` be used `:. 2xxn_(1)xx110=n_(2)xx1xx132` `:. (n_(1))/(n_(2))=(132)/(110xx2)=0.6:1`