Dear Student,
Please find below the solution to your problem.
500cm3 of 0.1 M HCl corresponds to 0.5×0.1=0.05 moles of hydrogen ions.
200cm3 of 0.2 M NaOH corresponds to 0.2×0.2=0.04 moles of hydroxide ions.
sodium hydroxide is completely neutralize by Hcl
The enthalpy of neutralisation is 57.3 kJ/mol.
For 0.04 moles, the enthalpy of neutralisation is 0.04×57.3=2.292kJ
Thanks and Regards