WELCOME BACK..
The first lesson we took on the first day we started school again, was MOLARITY, or Molar Concentration, of solutions.
A solution is a homogenous mixture that normally consists of
- a Solute, which is the smaller quantity, and
- a Solvent, which is, well, the bigger quantity
Concentration, is the amount of solute in a solution.
Molarity, is the number of moles of solute in one litre of solution.
The unit for Molarity is the number of moles per
litre, and can be extremely abbreviated (like the
case of "mole") to mol / L ..
It can also be an "M"
( must be capitalized )
So basically, the formula for Molarity is this ::
MOLARITY = moles of solute (mol)
volume (L)
So what do you think of this statement?
A 5 M solution is more concentrated than a 4 M solution.
hmmmmmmm
Take a minute to think about this, and give it the amount of thinkin git deserves... okay, DONE.
WELL, YEAH OBVIOUSLY..
( You get the point now )
So,, let's try some examples then>>
- Eg1--
Sea water contains 28.0 grams of NaCl per Litre,
what is the molarity?
First, you might want to convert grams to moles. This is the
equation now:
# of moles = 28.0 g X 1 mole = 0.479 moles
58.5 g
You already know you have a Litre, so you divide 0.479 by 1
and another minute or two to try to solve this.. Then you will
realize you got 0.479 M.
- Eg2--
What weight, in grams, of KCl is there in 2.50 Litres
of 0.50 M ??
First, get the number of moles by multiplying 0.50 M
& 2.50 L..
You will get 1.25 moles
Then convert moles to grams through this>>
mass = 1.25 moles X 74.6 g = 79.2 g
1 mole
This lesson is actually easy, those two examples is the hardest it can get..
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