Thursday, January 13, 2011

Diluting Solutions

Chemicals are usually shipped in their most concentrated form for convenience and transportation. 
We do not usually use the chemicals with that concentration, so we need to dilute them.

Key Idea: The moles of solute is constant before AND after diluting. (moles before = moles after)

M1L1 = M2L1

We can use this formula to find any one of those 4 pieces of information, as long as we have the other three.

Example: Concentrated HCl is at 11.6 mole/L. How would you make 250mL of 0.500 mole/L HCl?

You see you already have the 3 pieces of information that you need to determine what's unknown.

L1 = M2 x L2

(I just rearranged the formula to help us find what we are looking for, which was the volume that we began with.)

L1 = 0.500mole/L HCl x 250mL
11.6mole/L HCl

= 11mL

Now we know that we began with 11mL of solute. 

Are you this intense when it comes to Chemistry?

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