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Balance the following equations. (i) H_(3)PO_(3) to H_(3)PO_(4) + PH_(3) (ii) Ca + H_(2)O to Ca(OH)_(2) + H_(2) (iii) Fe_(2)(SO_(4))_(3) + NH_(3) +H_(2)O to Fe(OH)_(3) + (NH_(4))_(2)SO_(4) |
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Answer» Solution :(i) This equation can easily be balanced by hit and TRIAL method as follows. The formula `H_3PO_4` contains maximum number of atoms. Therefore, it can be selected to START with. On multiplying `H_(3)PO_(4)`by 3 and `H_(3)PO_(3)`by 4, we get: `4H_(3)PO_(3) to 3H_(3)PO_(4) + PH_(3)` In this equation, the atoms of each kind are the same on both sides of the equation. Hence, the equation is balanced. (ii) This equation can be balanced by hit and trial method. Writing hydrogen in the atomic FORM, we get `Ca + H_(2)O to Ca(OH)_(2) + H` `Ca(OH)_(2)` can be selected to start with because it contains maximum number of atoms. Oxygen present in it can be balanced by multiplying `H_2O` by 2 and hydrogen can be balanced by multiplying H by 2. Thus, we have: `Ca + 2H_(2)O to Ca(OH)_(2) + 2H` On writing the equation in the molecular form, we get the following balanced equation: `Ca + 2H_(2)O to Ca(OH)_(2) + H_(2)` (iii) This is a bit complicated equation. HOWEVER, it can be balanced by partial equation method. The partial equations corresponding to the probable steps of the given reaction are as follows. `Fe_(2)(SO_(4))_(3) + H_(2)O to Fe(OH)_(3) + H_(2)SO_(4)`.....(i) `NH_(3) + H_(2)SO_(4)to (NH_(4))_(2)SO_(4)` ..........(ii) On balancing these partial equations by hit and trial method, we get: `Fe_(2)(SO_(4))_(3) + 6H_(2)O to 2Fe (OH)_(3) + 3H_(2)SO_(4)`..........(iii) `2NH_(3) + H_(2)SO_(4) to (NH(4))_(2)SO_(4)`..........(iv) The intermediate species, i.e., H2S04 can be cancelled by multiplying Eq. (iv) by 3 and adding it to Eq. (iii). `Fe_(2)(SO_(4))_(3) + 6H_(2)O to 2Fe(OH)_(3) + 3H_(2)SO_(4)` `[2NH_(3) + H_(2)SO_(4) to (NH_(4))_(2)SO_(4)] xx 3` ------------------------------------------------------------------------ `Fe_(2)(SO_(4))_(3) + 6NH_(3) + 6H_(2)O to 2Fe(OH)_(3) + 3(NH_(4))_(2)SO_(4)` This is the final balanced equation. |
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