Question

How many grams of KOH required to make 500 mL of 8 M
Solution of KOH?

Answer 1

Given:

Volume of KOH solution = 500ml

Concentration of KOH solution = 8M

To find:

Grams of KOH required to make a solution.

Solution:

Molarity is a concentration term which may define as the ratio of moles of given solution present in one liter of solution.

Formula used for Molarity is-

    Molarity = $\frac{n}{V(L)}$

or, Molarity = $\frac{n}{V(ml)} \times 1000$

here, n = number of moles

        V = volume of solution

or, $n = \frac{Molarity \times V(ml)}{1000}$

     $n = \frac{8 \times 500}{1000}$

     n = 4 moles

so, the number of moles present in KOH solution is 4 moles.

now, we know that

            $n = \frac{w}{MM}$

here, n = number of moles

         w = mass of given KOH

         MM = molecular mass

Molecular mass of KOH = 39 + 16 + 1

                                        = 56 gmol⁻¹

therefore, substitute the value of MM and n, we get,

              w = MM × n

               w = 56 gmol⁻¹ × 4 mol

               w = 56 × 4 g

               w = 224 g

Therefore, 224 grams of KOH is required for making a solution of KOH of volume 500ml and concentration 8M.