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When `4g` of iron is burnt to ferric oxide at constant pressure, `29.28KJ` of heat is evolved. What is the enthalpy of formation of ferric oxide (At wt. of `Fe=56`)A. `-81.98KJ`B. `-819.8KJ`C. `-40.99KJ`D. `+819.8KJ` |
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Answer» Correct Answer - A Given: Weight of iron burnt `=4g` , Heat liberated `-29.28KJ` and atomic weight of iron `(Fe)=56` . We know that in ferric oxide `(Fe_(2)O)` , 2 moles of iron or `2xx56=112g` of iron are burnt. We also know that when `4g` of iron are burnt, then burnt, liberated `=29.28KJ` , therefore when `112g` of the iron are burnt, then heat liberated `=(29.28xx112)/(4)=-819.8KJ` (Minus sign due to liberation of heat). |
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