Question

What is the mass of KOH found in a 785 mL of a 1.43 M solution of KOH

Answer 1

Molarity is defined as the ratio of number of moles to the volume of solution in litres.

The mathematical expression is given as:

$Molarity = \frac{Number of moles}{volume of solution in litres}$

Here, molarity is equal to 1.43 M and volume is equal to 785 mL.

Convert mL into L

As, 1 mL = 0.001 L

Thus, volume = $785\times 0.001$ = 0.785 L

Rearrange the formula of molarity in terms of number of moles:

$Number of moles =molarity\times volume of solution in litres$

n = $1.43 M \times 0.785 L$

= 1.12255 mole

Now,  Number of moles  = $\frac{mass in g}{molar mass}$

Molar mass of potassium hydroxide  = 56.10 g/mol

1.12255 mole  = $\frac{mass in g}{56.10 g/mol}$

mass in g = $1.12255 mole\times 56.10 g/mol$

= 62.97 g

Hence, mass of $KOH$ = 62.97 g