the mole chapter 10 formula mass: is what a single molecule “weighs” in amu’s (atomic mass...
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The Mole
Chapter 10
Formula Mass:
Is what a single molecule “weighs” in amu’s (atomic mass units)
Revision:
So, 1 molecule of Water (H2O) weighs:2 x 1.01 (for H) + 1 x 16.00 (for O)= 18.02 amu’s
Example #2:What is the mass of 1 molecule of
Sugar(Sucrose)? (C6H12O6)
C: 6 x 12.01 =H: 12 x 1.01 =O: 6 x 16.00 =
Do other examples?a) CO2
b) (NH4)2CO3
The Mole:First, let’s look at names that reflect
numbers:
1 dozen =
1 baker’s dozen =
1 score =
1 gross =
Let’s now focus on a particular isotope – Carbon-12
1 Carbon-12 atom weighs ______________But this is an impractical measurement. We
want to work in the mass unit of grams.So, how many atoms of Carbon-12 would it
take to weigh 12.00 g.?
Amadeo Avogadro (Italian, 1776-1856) calculated the number to be 6.022 x 1023
and is also known as aSo now, the average atomic mass number also
represents how many grams that element would weigh if you had 1 mole of that substance.
So, 1 mole of Water weighs:H: 2 x 1.01 g/mole = 2.02 g/moleO: 1 x 16.00 g/mole = 16.00 g/mole
This # is known as the _____________(mass
of 1 mole) of Water.Examples. Calculate the Molar Mass of the
following:a.) SO2
b.) (NH4)3PO4
Mole to Mass & Mass to Mole ConversionsIf we are given the # moles of a substance and
we want to calculate how much it weighs (i.e. what’s its mass?), then we convert by using the _________________________!
E.g. What is the mass of 1.50 moles of Water?
1.50 mol. Of H2O x 18.02g of H2O = 27.03g of H2O
1 1 mol. of H2O
E.g.#2 What is the mass of 0.75 mol. Of Salt?
Now, going the other way.How many moles are in 100.g of CO2 ?
100.g of CO2 x 1 mol. of CO2 = _______________
1 44.01g of CO2
E.g.#2 How many moles are in a pound of Sugar?
Converting from moles to molecules & vicy versi
In these conversions, instead of using the _________________________, you use Avacado’s Avagadro’s Number. (NA)
Ex. How many molecules are in 1.50 moles of Water?(remember: 1 mole = 6.02 x 1023 )
1.50 mol. x 6.02 x 1023 molecules = ___________________1 1 mol.
Ex.2) How many moles in 2.107 x 1024 molecules of Salt?
2.107 x 1024 molecules x ____ = 3.50 moles
1 6.02 x 1023 molecules
Do these in-class egg samples:1.) How many molecules are in 0.02 moles
of Sugar?
2.) How many moles are in 3.01 x 1023 molecules of O2?
Let’s look at lotsof moleculesof Water.
Time to draw a MOLE diagramI know what you’re thinking! Now we can doMass to Molecules conversions & vicy versi.(Hint: it’s a 2 step Chain Method)Ex. How many molecules are in 12.0g (~½ oz) of
Water?
12.0g of H2O x _____________x________________________1 1 mol of H2O
= 4.00 x 1023 molecules of H2O
Ex. What does 9.03 x 1022 molecules of Vitamin C weigh?
(Vitamin C = C6H8O6)
The Volume occupied by 1 mole of a gas is the Molar Volume.
The Volume occupied by 1 mole of a gas @ STP is known as the Standard Molar Volume of a gas and is equal to 22.4 L.
@ STP
V = 22.4 L/mol. V = n x 22.4 L/mol.n
So 1 mole of any gas occupies 22.4L @ STP, but their masses may be different.
Standard Molar Volume
So 2 moles of a gas will occupy twice the space (Volume) of 1 mole.
e.g. 2H2 + O2 2H2O
(more examples: N2 + H2 NH3 ,…)
And remember:1 mole = 6.02 x 1023 molecules
(Diagram – New Mole Diagram)
Add that to the mole diagram…
Mass (Grams) Mole
Volume @STP
Molecules/ Atoms