Calculate the molarity and normality of a solution containing 0.5 g of NaOH dissolved in 500 ml. solution-

Weight  of NaOH dissolved = 0.5 g

Volume  of NaOH Solution = 500 ml 

Calculation of molarity 

0.5 g of NaOH $=\frac{0.5}{40}$ moles of NaOH

[$\because$ Mol. wt. of NaOH = 40]

                        = 0.0125 mole 

Thus 500 ml of the solution contain 

NaOH = 0.0125 mole

$\therefore$ 1000 ml of the solution contain 

$=\frac{0.0125}{500}\times 1000=0.025\mathrm{M}$

Hence molarity of the solution = 0.025 M

Calculation of normality

Since NaOH is monoacidic; 

Eq. wt. of NaOH = Mol. wt. of NaOH = 40 

$\therefore$ 0.5 g of NaOH

$=\frac{0.5}{40}$ g equivalents = 0.0125 gram equivalents 

Thus 500 ml of the solution contain NaOH = 0.0125 g equiv. 

$\therefore$ 1000 ml of the solution contain

$=\frac{0.0125}{500}\times 1000=0.025$

Hence normality of the solution = 0.025 N