`AI_(2)O_(3)` Soluble in "NaOH" due to formation of

Ag_(2)S is soluble in NaCN due to formation of

$ White ppt. of AgCl is soluble in NH_(4)OH ! It is due to the formation of soluble complex.

When 10g of AI is used for reduction in each of the following alumino thermic reactions. Which reaction would generate more heat and by hwo much? a. 2AI + Cr_(2)O_(3) rarr AI_(2)O_(3) +2Cr b. 2AI +Fe_(2)O_(3) rarr AI_(2)O_(3) +2Fe Standard heat of formation of AI_(2)O_(3), Cr_(2)O_(3) , and Fe_(2)O_(3) are -1676 kJ, 1141 kJ , and -822.2 kJ , respectively.