Question

The molarity of a sodium hydroxide solution by dissolving 4 grams of it in 250 ml aqueous solution.
(a) 0.8 M
( b) 0.1 M
(c) 0.2 M
(d) 0.4 M

Answer 1

$\green{Given}$

• Mass of NaOH = 4 gram.

• Volume of the solution = 250 ml

$\green{To \: Find }$

Molarity of the solution

$\green{Formula}$

$\boxed{ \blue{molarity \: = \frac{no \: of \: moles \: of \: solute}{volume \: of \: solution} \: } \: }$

$\green{Calculations}$

We know, Molar mass of NaOH = 40 gram.

Hence, number of moles of NaOH in its 4 gram solution =

$\pink{ \frac{given \: mass}{molar \: mass} \: \: = \frac{4}{40} = 0.1}$

Using formula of molarity ( Volume = 250 ml = 0.250 l )

$\boxed{molarity \: = \frac{0.1}{0.250} = 0.4 \: }$