$a,PTHH:4Al+3O_2\xrightarrow{t^o}2Al_2O_3 b,n_{Al}=\dfrac{4,05}{27}=0,15(mol)\\ \Rightarrow n_{Al_2O_3}=\dfrac{1}{2}n_{Al}=0,075(mol)\\ \Rightarrow m_{Al_2O_3}=0,075.102=7,65(g)\\ c,n_{Al_2O_3}=\dfrac{25,5}{102}=0,25(mol)\\ \Rightarrow n_{O_2}=\dfrac{3}{2}n_{Al_2O_3}=0,375(mol)\\ n_{Al}=2n_{Al_2O_3}=0,5(mol)\\ \Rightarrow V_{O_2}=0,375.22,4=8,4(l)\\ m_{Al}=0,5.27=13,5(g)$

`a)``PTHH` là `:`

         `4Al``+``3O_2`$\xrightarrow[]{t^o}$`2Al_2``O_3`

`b)``nAl``=``\frac{m}{M}``=``\frac{4,05}{27}``=``0,15` `(mol)`

`PTHH`            `4Al``+``3O_2`$\xrightarrow[]{t^o}$`2Al_2``O_3`

                       `0,15`                    `0,075`    `mol`

`mAl_2``O_3``=``n``.``M``=``0,075``.``102``=``7,65` `(g)`

`c)``nAl_2``O_3``=``\frac{m}{M}``=``\frac{25,5}{102}``=``0,25` `(mol)`

`PTHH`            `4Al``+``3O_2`$\xrightarrow[]{t^o}$`2Al_2``O_3`

                       `0,5`      `0,375`      `0,25`     `mol`

`mAl``=``n``.``M``=``0,5``.``27``=``13,5` `(g)`

`VO_2``(đktc)``=``n``.``22,4``=``0,375``.``22,4``=``8,4` `(l)`