Derived units Density is g mL Area m x m m 2 Molarity molar concentration concentration mole litre molL or M for short It is the number of moles per litre c molar concentration in molL ID: 345473
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Slide1
MolaritySlide2
Derived units
Density is g/
mL
Area = m x m = m
2
Molarity
= molar concentration = concentration = mole/
litre
= mol/L or M for short.
It is the number of moles per
litreSlide3
c = molar concentration in mol/L
n = number of moles
v = volume in
litres
Thus c = n/v.
We can create a magic triangle for this one too.Slide4
Square brackets
We can also say something is about its concentration by putting SQUARE BRACKETS around its chemical formula
[
NaOH
]
[HCl]
[
NaCl
]
[CH
3
COOH]Slide5
Note
The more concentrated something is
The more moles are present in our volume
Moles = # of particles
So more moles = more particles
More particles in our volume = more concentratedThink of juiceSlide6
Calculations involving molarity
If you are given a mass in grams, you can convert it to moles. With the moles, if a volume in
litres
is given, you can find the concentrationSlide7
Example
What is [
NaOH
] when 50.00g of
NaOH
is dissolved in 500mL of solution?Slide8
Example
What is the
molarity
of pure ethanol, C
2
H5OH, having a density of 0.789g/
mLSlide9
Dilution
We cannot always work with high concentration solutions. Acids being too high concentration can be dangerous to work with.
We will want to lower its concentration from an economical and safety standpoint.
We dilute thingsSlide10
Dilution equation
C
conc
x
V
conc = C
dil
x
V
dil
We shorten it to
C
1
V
1
= C
2
V
2Slide11
Example
What [
HCl
] is used when 1.5L of the original solution is diluted to form 4.5L of 0.300M of
HCl
?Slide12
Example
If 0.400L of 0.200M
NaOH
is mixed with 0.800L of 0.500M
NaOH
. What is the resulting [NaOH] in the mixture?
Tricky question.Slide13
NOTE
The resulting concentration is in between the two starting concentrations.
It can never be BELOW the lowest concentration
It can never be ABOVE the highest concentrationSlide14
Homework
Pg 97 #56, 58
Pg 98 #59, 60, 67
Pg 102 #78, 80, 84, 86, 89