H$3-3$:

The air contained in a piston$-$cylinder device is initially at $3$ MPa and $305$ K with a volume of $0\mathrm{.}5m^3$

$($State $1).$ The air then undergoes a constant pressure process and the temperature of the air changes to

$680$ K $($State $2).$ Determine

$($a$)$the mass of the air contained in the piston$-$cylinder device;

$($b$)$the change of the internal energy associated with the total mass of the air.

Answers: $($a$)17\mathrm{.}14$ kg ; $($b$)4\mathrm{.}78$ MJ $.$