December 2 2009

In todays class we learned about giving directions for dilution of solutions and learn about dilution of solutions itself.

To give directions to a experiment we must first find the information we need.
concentration > moles > mass

concentration = n/v
N represents number of moles
V represents the volume

Once you find all of that you would tell them how much volume to measure how much grams of the solution you would put in and finally add the solution itself.

Example: Son needs to make a 4M solution of CaCl2. If he needs 2 L what procedure will he use?
4 mol x 2 L = 8mol
4 mol x 111g = 444g
Now we have all of the information we need
1) first measure 2L of water in your test tube
2) weigh 444g of CaCl2
3) add the CaCl2 to the water and stir the solution

We also learned about the dilution of solutions which is when you add water to the concentration it decreases. If the volume is doubled then the concentration would be halved. If the volume is halved then the concentration would be doubled.

4 L = 2M <--- what were starting with
8L = 1M <--- multiply 2 volume divide the M by 2
2 L = 4M <------ divide the volume by 2 multiply the M by 2

to solve for dilution of solutions we would use C1V1 = C2V2
C1 = initial concentration
C2 = final concentration
V1 = initial volume
V2 = final volume

An example would be:
If 30mL of .67M of NaBr is diluted to a total volume of 60ml what is the final Molarity of the solution?

C1 = .67M
C2 = ?
V1 = 30ml
V2 = 60ml

C2 = (V1)(C1)/V2 C2 = (30ml)(.67M)/60ml C2 = .34M\

Video helping to solve dilution of solutions:


Heres a link on Dilution of Solutions:
http://www.emsb.qc.ca/laurenhill/science/cv.html