Question

If 40.0 mL of a `3.0x10^(-5)` solution is diluted to 100 mL, what is the resulting concentration?

Answer 1

`M_f=1.2xx10^(-5)M`

Explanation:

When a solution is diluted, the number of mole of particles in the solution does not change.

The relationship between the number of mole `n` and the molarity `M` is the following:

`M=n/V=>n=MxxV`

where, `V` is the volume of the solution.

If we consider that initially the volume and the molarity are:

`M_i=3.0xx10^(-5)M`

`V_i=40 mL`

What would be the final molarity `M_f=?` when the final volume is `V_f=100mL`?

since the number of mole does not change, we can write:

`M_ixxV_i=M_fxxV_f`

`=>M_f=(M_ixxV_i)/(V_f)=(3.0xx10^(-5)Mxx40cancel(mL))/(100cancel(mL))=1.2xx10^(-5)M`

Here is a video that discusses the solution preparation and dilution:
Lab Demonstration | Solution Preparation & Dilution.