Because of sealed vessel ΔV=0
So, ΔW=0
from ideal gas equation -
ΔQ=ΔU+ΔW
ΔQ=ΔU
we know that -
ΔU=nCvΔT=mM×f2RΔT
=mM×52RΔT.....(1)
ideal gas equation - PV = nRT=mMRT
=mMR=PVT
put the value of mM in equation -
ΔU=ΔQ=PVT×52ΔT
=(1.013×105)(5×10−3)273×52×(−55)
=-255 J