Question

How much water should be added to 5.00 g of KCI to prepare a 0.500 M solution?

Answer 1

133.4 `cm^3`

Explanation:

Molarity is number of moles of solute divided by number of litres of solution.

`M=n/V`

Rearrange for V to give `V=n/M`

Number of moles of KCl is the mass divided by the molar mass of KCl which is 75.5 g/mol, so (5/75.5) = 0.0667 moles.

Now plug in the numbers: `V=n/m = 0.0667/0.5 = 0.1334` litres

So you need to add 0.1334 litres of 133.4 `cm^3` of water.

(NB: symbol for molarity is upper case M. m is metres).