Saved Bookmarks
| 1. |
The value of Delta_f G^@ for the formation of Cr_2 O_3 is -540 KJ mol^(-1) and that of Al_2 O_3 is -827 KJ mol^(-1). Is reduction of Cr_2 O_3 possible with Al ? |
|
Answer» Solution :The TWO EQUATIONS are : `(i) 4/3 Al (s) + O_2 (g) to 2/3 Al_2 O_3 (s)Delta_f G^@ (Al, Al_2 O_3) = -827 KJ mol^(-1)` (ii) `4/3 Cr (s) + O_2 (g) to 2/3 Cr_2 O_3 (s) ""Delta_f G^@ (Cr, Cr_2 O_3) =-540 KJ mol^(-1)` SUBTRACTING eqn. (ii) from eqn (i), we get `4/3 Al (s)+ 2/3 Cr_2 O_3 (s) to 2/3 Al_2 O_3 (s) + 4/3 Cr(s) "" Delta_r G^@ =-287 KJ mol^(-1)` Since `Delta_r G^@` for the combined REACTION is -ve. therefore , the above reaction, i.e. reduction of `Cr_2 O_3` by Al is POSSIBLE. |
|