By using the following formulas:
molarity= no of mol of NaOH/volume
no of mol of NaOH= mass/molar mass
the molarity of the solution can be easily determined.
Mass of NaOH= 23+16+1 =40
then put this value in this formula
no of mol of NaOH= mass/molar mass
and after calculating the no. of moles.
put the value in this formula
molarity= no of mol of NaOH/volume
and molarity will be 0.500 M.