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Which of the following observations made from the Ellingham diagram is wrong ?A. The slope of the curves of the formation of metal oxides is negativeB. Each curve is straight line except when some change takes place in phase `(S - 1 or 1 rarr g)`C. In the case of less reactive (or less electroposities metal like `Ag and Hg, Delta G^(Ө)` become positive at relatively low temperatures .D. Any matel oxide with lower value of `Delta G^(Ө)` is more stable than a metal oxide with higher `Delta G^(Ө)` . |
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Answer» Correct Answer - a Consider the formation of a metel oxide `(M_(2)O)` `2sM(s) + O_(2)(g) rarr 2M_(2)O(s)` Is this reaction there is decreases in the value of `Delta S` ior `M_(2)O` solid and `O_(2)` is a gas i.e. `Delta S` is negative .This if temperature is increases `T Delta S` becomes . becomes more negative as is the equation `Delta G = Delta H - T Delta S Delta H ` is tengative formation of metal oxide is enothermic and `T Delta S` (it negative quantity ) is substrcted `Delta G` becomes less negative i.e. `Delta G` is likely to increases with rise it in temperature and ythis trend is confirmed from the corves of metal oxide its Ellingham diagram .The slope of the curve of th e formation of metal oxides is `- ve` because `Delta G` becomes less negative or temperature with the rise in temperature The temperature at which such a change occure is indicated by an incrfeases in the slope on the `- ve` side for example , in the `Zn- ZnO` "`curve , "the melting of Zn is incates by the first abropt increases in the" `-ve` "slope at temperature" `692K`. "The indicates that both silver oxide (Ag,O) and merccury oxide (HgO) are unstate and decompose at relatively low temperature" `2Ag_(2)O overset (Delta) To 4Ag + O_(2)` `2HgO overset (Delta) To 2Hg + o_(2)` This amples that the metal oxide placed higher to the diagram can be reducted by the metal invcolved in the formation of the oxide placed lower in the diagram. For example by `Ct`, ` Ct_(2) O_(3) + Al rarr Al_(2)O_(3) + 2Ct` ltvbrgt Thus the relactive tendency of the various metalsto act in reducing agents is `Cu gt Mg gt Al gt Cr gt Zn gt Fe gt Ni` |
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