@Ritwik_Kapoor what you did in Q.4 is the calculation of Enthalpy Change, and not the Energy or Heat Change to the System.
\Delta H is the enthalpy change associated with the system, and \Delta Q is the Heat Change associated with the system.
Thus, what we have to use here is the First Law of Thermodynamics : \Delta U=\Delta Q+W
Since : W=-P\Delta V , thus we have :
\Delta Q=\Delta U+P\Delta V
As per the given data, we have :
\Delta V=-200cc \to \Delta V=-0.2L (Contraction)
\Delta Q=-8.5J (Heat Lost) and P=0.5 atm.
Thus : \Delta Q=\Delta U+P\Delta V
\to -8.5=\Delta U+[0.5(-0.2)×101.3]
( 1 Latm = 101.3J )
Thus, \Delta U=10.13-8.5 \to \Delta U=1.63J
Do let me know if u have any doubts.