Diluting Solutions to Prepare Workable Solutions



Moles of solute stays the same,
concentration depend on amount of water



Chemicals are shipped around the world in their most concentrated form, like powder, making it easier and lost costly because then we wouldn’t be shipping all that extra water.

This is why we need to be able to make solutions of any concentration from a more concentrated source.

The moles of the solute is always constant.

The concentration is based on the amount of water present.

MOLES OF SOLUTE BEFORE  =  MOLES OF SOLUTE AFTER

or

M1L1  =  M2L2

Where:

M = Moles

L = Litres

Eg.  15.0mL of 0.70M KCl  solution is diluted to a final volume of 150.0mL. What is the new concentration?

M1 =  0.70M

L1  =  15.0mL

M2 = ?

L2  = 150.0mL

M1L1  =  M2L2

0.70M  x 15.0mL = M2  x 150.0mL

0.70M x 15.0mL  =   M2

150.0mL          .

0.070M  =  M2

Eg.   A 0.275M solution is concentrated by evaporating the a reduced volume of 250.0mL and a molarity of 0.720M. What is the original volume?

M1 =  0.275M

L1  =  ?

M2 = 0.720M

L2  = 250.0mL

M1L1  =  M2L2

0.275M  x  L1 = 0.720M  x  250.0mL

L1  =  0.720M  x  250.0mL

       0.275M

L1  =  912mL

By:  JZ