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 = (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* 0.001` = 0.785 L

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

`Number of moles =molarity* volume of solution in litres`

n =
`1.43 M * 0.785 L`

= 1.12255 mole

Now, Number of moles =
`(mass in g)/(molar mass)`

Molar mass of potassium hydroxide = 56.10 g/mol

1.12255 mole =
`(mass in g)/(56.10 g/mol)`

mass in g =
`1.12255 mole* 56.10 g/mol`

= 62.97 g

Hence, mass of
`KOH` = 62.97 g