calculate molarity of NaOHin the solution prepared by dissolving its 4g in enough water to form 250ml of this solution ?

Answer 1

mols NaOH = grams/molar mass
The M = moles NaOH/L soln.

Answer 2

molarity=moles of solute/volume of whole solution in litres
so the mass of Na/molar mass of NaOH all divided by .250Litres

4g/40g divided by .250 litres is .4 M.
The answer is .4