### dilutions?

Posted:

**Sat Oct 06, 2018 8:25 pm**Could someone please explain to me the general steps for how to complete a dilution problem?

Created by Dr. Laurence Lavelle

https://lavelle.chem.ucla.edu/forum/

https://lavelle.chem.ucla.edu/forum/viewtopic.php?f=10&t=33214

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Posted: **Sat Oct 06, 2018 8:25 pm**

Could someone please explain to me the general steps for how to complete a dilution problem?

Posted: **Sat Oct 06, 2018 9:23 pm**

The exact steps may vary depends on the types of values are given. The key concept is that when diluting a solution, the moles of solute remain the same. The moles of solute = M initial × V initial = M final × V final. So it might be helpful to first think about which of those quantities were given, try to plug in some numbers, and then solve for the unknown one.

Posted: **Sun Oct 07, 2018 12:31 am**

m1v1=m2v2 will be your best friend! Also, here is Lavelle's video module on molarity and dilution of a solution!

https://lavelle.chem.ucla.edu/wp-conten ... n.wmv.html

https://lavelle.chem.ucla.edu/wp-conten ... n.wmv.html

Posted: **Sun Oct 07, 2018 12:24 pm**

M1V1=M2V2 is the main equation for dilutions! M=n(mol)/v(l) and you can move the equation around depending on your given in the problem. Also make sure all the units are the same in your equation.

Posted: **Sun Oct 07, 2018 10:06 pm**

I solved most dilution problems by using the equation Molarity(M)= mol of solute (n) / vol of solution (V). From this equation, we know that when diluting the solution, the moles of solute remain the same. So, n(initial)=n(final), and also M(initial)V(initial)=M(final)V(final). Using this formula, problems usually give 3 of these 4 values needed, so I can manipulate the formula to find the missing value.

Posted: **Sun Oct 07, 2018 10:15 pm**

Sometimes the problem won't directly give you the initial molarity, so you might have to convert the given mass of solute to moles. Then divide by the volume of the solvent to find the initial molarity.