Question

molarity of 25% w/v NaOH
solution

Answer 1

AnswEr :

Given that,

25 % W/V of Sodium Hydroxide

Mathematically, 25 parts of NaOH by mass are present in 100ml of the solution.

• Given Mass of NaOH (m) = 25g.

• Volume of the solution (v) = 100ml

To finD :

The molarity of the solution.

$\large{\star \ \boxed{\boxed{\sf M = \dfrac{n}{v_{ml}} \times 10^3 }}}$

Now,

Number of moles of NaOH in given solution is,

$\sf n = \dfrac{given \: mass}{molar \: mass} \\ \\ \implies \sf \: n = \dfrac{25}{23 + 32 + 1} \\ \\ \implies \: \sf \: n = \dfrac{25}{40} \\ \\ \implies \: \sf \: n = \dfrac{1}{8} \\ \\ \implies \boxed{ \sf \: n = 0.125 \: mol.}$

Thus,

$\sf \: Molarity = \dfrac{0.125}{100} \times 1000 \\ \\ \longrightarrow \: \sf \: Molarity = 125 \times {10}^{ - 3} \times 10 \\ \\ \longrightarrow \underline{ \boxed {\sf \: Molarity = 1.25 \: M}}$

$\therefore$ Molarity of the solution is 1.25 M