It is when you make a liquid less concentrated by adding water or another solvent to it.
So why do we do this?
Chemicals shipped around the world are usually in their most concentrated forms. If they were not, we would be shipping lots of water with the chemicals, making the shipping very cost ineffective.
So, once we get the chemicals, we need to make solutions of the concentration from a more concentrated source.
For example, if there were 2.00 L of KCl of 16.0 M (molarity), we don't need all of the substance in order to create a solution of 0.800 L of 2.00 M HCl.
Here's how we calculate it.
We know that the moles of the solute is always constant, according to the Law of Conservation of Mass. We are only really adding more water to make a less concentrated solution.
A solution is prepared by dissolving a solute in a solvent.
The formula: M1L1 = M2L2
1st step: Figure out how much volume is needed to start (L1)
From the above example:
16.0 L1 = 2.00M X 0.800 L
16.0 L1 = 1.60
16.0 16.0
L1 = 0.100 L (Don't forget sig figs.)
Next: We can determine how much water is necessary by subtracting L1 from the number of litres in the solution (L2).
Therefore, 0.800L - 0.100L = 0.700L
This means we need to add 0.700 L of water to the 0.100L substance in order to get our solution of 0.800L with a molarity of 2.00M.
If there are still things you don't quite understand, you can always check out these websites for more help.
http://www.ausetute.com.au/dilucalc.html
http://www.sci.sdsu.edu/classes/chemistry/chem467l/mardahl/dil.html
http://dl.clackamas.edu/ch105-04/dilution.htm
Here's a video from chemistryprofessorpc:
No comments:
Post a Comment