Molar NaCl
 
No. of moles = weight of substance/Molecular mass
= 250/58.44
(58.44g is the molecular mass of NaCl)

Molar NaCl

No. of moles = 250g/58.44g = 4.278 moles

Therefore, molarity = 4.278/2L =
Molarity = no. of moles of substance/Litres of solution