Question

To what volume should 5.0 g of `KCl` be diluted in order to prepare 0.25 M solution?

Answer 1

0.27 L

Explanation:

We are looking for volume and are given a mass and a molarity.

Note:

`M=(mol_(solute))/(Liters_(solution))`

Rearranging this equation to solve for volume:

`L_(solution)=(mol_(solute))/M`

We have M, but we need `mol_(solute)`. To get this, we use the molecular weight of KCl, which is:

`74.55 g_(KCl)/(mol_(KCl))`

To get the moles of KCl:

`5.0 g_(KCl)*(1 mol_(KCl))/(74.55g_(KCl))=0.067mol_(KCl)`

Finally, plug back into the equation for `Liters_(solution)`:
`L_(solution)=(mol_(solute))/M`
`L_(solution)=(0.067mol_(KCl))/(0.25*(mol_(KCl))/(L_(solution))`
`L_(solution)=0.27 L`

Note: This is the total solution volume, not the volume of solvent. Total volume of solute + solvent is the solution volume.