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Review of MgO, Properties 5 <br /> When v/eP ut M902 in water, via are trying to make the reaction [1) or [2] go <br /> "backwards" from the way I have them written. The thermodynamic answer does not <br /> change and thus, one would get any different amount of HA. The amount calculated <br /> based on the equilibrium constant calculated from the free energy of the reaction in <br /> Table 1 is very small, and is on the order of 10'" motes per lit-sr. <br /> However, this does not preclude other reactions from going on at the same time. In <br /> general, one has to solve all the reactions simultaneously to see what is going on. One <br /> such reaction, when we put MgO2 in `'rater is: <br /> 2 PAgOz 2 H2O - 2 Mg (ON),T 02 (3j <br /> If one does t;ne frea energy calcu!Y,ion for this experiment, o„e will find that it is also <br /> very large and very nega`ive. The reaction, and thus the release of oxygen from <br /> magnesium peroxide is driven by the forma-'ion of magnesju:n hydroxide. In the early <br /> E°70's �'r� ra�'ized th=t t;ne only thing that keeps P402 s':ab'._ is how slow this reaction <br /> f;liOht ba once'( tine conditio,-is of Use. It 15 not t�� revers 0' �����`'.IOn [1) u�ai i5 <br /> iMOoriant but rather limiting the kinetics of equa`ion (3). <br /> • _ normally ca.al, 7e t;-je cecomoosition of H 0 <br /> It should be nosed that tn:n�J t,n�: will norm, } f�- � 2 2 <br /> (reducing agents) would a,so be expected to ca!alyze equa`i_ � [5). Thus, t;ne fact that <br /> c2tala5� E,`ieCiS the deCO�iip05itiO,n Is not surprising. The c�:n�j�ic eiiECts d0 no' prove <br /> that reaction [1) is "violated" in the thermodynamic sense. <br /> If equation [8) represented a s,,mple kine,ic me-hr-n,sm, the fallowing would be true: <br /> -d [I';130z )Idt = dt'OZ )!dt = kY [i,1g02 ) [0: ) [g) <br /> vi-here the derivatives ere Nvith respect to ti<<ie. Si,n:e `va:er is relative cons!ant in the <br /> reaction if `va are dealing vAth flooded sys',ems equ=tion [9) the release of oxygen <br /> becomes: <br /> d (02 )!dt = k[Mg02 ) = k,�rl, - k [O2 ) ('01 <br /> where Mo designates the initial concentra`.ion of MaID, and v.e have made use of the j <br /> molecular balance: <br /> • <br /> [Mg02 ) - 1~111- 102 <br /> This simply says that the moles of oxygen and t"902 must add up to some initial ialue <br /> Of tAg02 . Nota that it does not matter whather M. refers to iha total amount of MgO2 in <br />