Some Basic Concepts of Chemistry Part 1

We known that no. of moles =Vlitre × Molarity & No. of millimoles =Vml× Molarity
so millimoles of NaOH=250×0.5=125
Millimoles of HCl=500×1=500
Now reaction is
so millimoles of HCl left =375
Moles of HCl=375×10−3
No. of HCl molecules =6.022×1023×375×10−3
=225.8×1021
≃226×1021=226