Chemical Thermodynamics Question 474
Question: The standard heat of combustion of Al is $ -,837.8,kJ,mo{{l}^{-1}} $ at $ 25^{o}C $ . If Al reacts with $ O_2 $ at $ 25^{o}C, $ which of the following releases 250 kcal of heat-
Options:
A) The reaction of 0.624 mole of Al
B) The formation of 0.624 mole of $ Al_2O_3 $
C) The reaction of 0.312 mole of Al
D) The formation of 0.150 mole of $ Al_2O_3 $
Show Answer
Answer:
Correct Answer: B
Solution:
- $ 2,Al+\frac{3}{2}O_2\xrightarrow{{}}Al_2O_3; $
$ \Delta H^{o}=-,837.8,kJ,mo{{l}^{-1}} $
2 mol 1.5 mol 1 mol 1 mol 0.75 mol 0.5 mol $ 837.8,kJ,mo{{l}^{-1}}\equiv $ Combustion of 1 mole Al or formation of 0.5 mole $ Al_2O_3 $
$ 250,kcal=\frac{250\times 8.314}{2},kJ $
$ =1.24,mol,Al $
or $ =0.62,mol $ of $ Al_2O_3 $
