Answer
a) $T_f=468K$
b) the final temperature will decrease
Work Step by Step
(a) We can find the final temperature as follows:
$T_f=\frac{2(Q-W)}{3nR}+T_i$
We plug in the known values to obtain:
$T_f=\frac{2(3280-722)}{3(1)(8.31)}+263$
$T_f=468K$
(b) We know that the final temperature will decrease because of more molecules and the average energy gained per molecule will also decrease.
