The standard heat of combustion of Al is `-840kJ mol^(-1)` at `25^(@)C`. If Al reacts with `O_(2)` at `25^(@)C`, which of the following release 280kJ if heat?

Options

A. The reaction of `(1//1.6)` mol of Al
B. The formation of `(1//1.6)` mol of `Al_(2)O_(3)`
C. The reaction of `(1//3)` mol of Al
D. The formation of `(1//6)` mol of `Al_(2)O_(3)`

Answer

C, D

Explanation

`Al+(3)/(2)O_(2)rarr(1)/(2)Al_(2)O_(3)`
`27g " " 51g`
`DeltaH=-840kJmol^(-1)`
`because 840kJrarr(1)/(2) mol Al_(2)O_(3)`
`therefore 280kJ rarr (1)/(2)xx(280)/(840)=(1)/(6)"mol"Al_(2)O_(3)`