Calculate the mass of na2co3 required to prepare 250ml of 0.5n solution

Concentration = 0.5 N
volume = 250 ml = 250 cm^3 = 0.250 dm^3
moles = conc. × vol.
= 0.5 × 0.250
= 0.125
mass = moles × relative molecular mass

so relative molecular mass if Na2CO3
= (23 × 2 ) +( 12 × 1 )+ (16 × 3 )
= 46 + 12 + 48
= 106

mass = 0.125 × 106
= 13.25 g

Hope it helped !!