# The Mole The Mole Chapter 7 Chemical

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```					   The Mole
Chapter 7
Chemical Quantities
What’s a mole anyway?
Well do you remember how to find
the molecular mass of a substance?
Get out a periodic table. Find the
atomic mass of carbon. What is it?

12
What unit goes at the end?

 Amu (u) or atomic mass units.
 Well it so happens that if you take that same
number and put grams instead of u, you have
one mole of that substance.
 In other words, trade u for g and you now
have a mole of carbon.
 So one mole of carbon is 12 grams of carbon.
Scientists use moles because
atoms and molecules are too tiny
balances are used to measure
atoms and molecules in grams.
How many grams of carbon in 4
moles of carbon?

48 g
How many moles of carbon
are there in 500 g of carbon?
500 g (1 mol)
( 12 g)
How many moles of carbon
are there in 500 g of carbon?
41.6 mole
How many moles of oxygen
are there in 500 g of oxygen?
500 g (1 mol)
( 16 g)
How many moles of oxygen are
there in 500 g of oxygen?
500 g (1 mol)= 31.25 mol
( 16 g)
 How many grams of calcium must be
weighed out in order to obtain a
sample containing 3 moles of atoms?
 a) 40 g
 b) 3 x 6 x 1023 g
 c) 120 g
 120 g
What is the difference
between molecular
mass and molar mass?
Molecular mass is
in atomic mass
units; molar mass
is in grams.
Find the number of moles in
24 g of CO

24 g     (1 mole)
( 28 g )
= 0.86 moles of CO
Convert 872 g of
ammonium oxide
into moles.
First find the correct
formula for ammonium
oxide.
(NH4)2O
Find the molar mass
of ammonium oxide
(NH4)2O
N – 2 x 14 = 28
H–8x1= 8
O – 1 x 16 = 16
Find the molar mass
of ammonium oxide
(NH4)2O = 52 grams
Set up a conversion
factor to change from
872 g to moles.
Conversion factor

872 g ( 1 mol)
52 g
= 16.8
What is
number?
6.02 x10 23

units of a
substance
44. Which of the following equals
9.2 x 1024 divided by
6.3 x 104?
A. 1.46 X 1024
B. 1.46 X 10 20

C. 1.46 X 10 6

D. 1.46 X 1028
6.02 x 10 23 , is also called a
mole, in the same way that
500 sheets of paper is called
a ream, or 144 is referred to
as a gross.
http://www.wiredchemist.com/chemis
try/instructional/chem_modules_mole
_lecture.html
 How many ping-pong balls are there in a mole of
ping-pong balls? What would their molar mass
be if one ping-pong ball weighs 1.0 g?
 6.02 x 1023 ping-pong balls in a mole of ping-
pong balls.
 If each ball weighs 1.0 grams, the molar mass
will be 6.02 x 1023 g.
 We would normally express this as 6.02 x 1023
g/mole.
 Are you saying that we can have a mole of
anything? Sure, can't you have a dozen
pencils, a dozen ducks, a dozen bricks?
However, we normally use the term mole in
dealing with atomic particles--atoms, ions,
molecules.
 How many atoms are present in 31 g of
phosphorus?
 a) 1 mole        b) 6.022 x 1023
 c) Avogardro's number d) a, b, and c
 All three are correct
 Your Zork particle counter has just
informed you that there are 3 x 1020
How many moles of radon is this?
 3 x 1020 particles/ 6 x 1023 particles
per mole) = 5 x 10-4 mole.
 Your lab partner is staring out the window as usual
when he suddenly exclaims, "Gadzooks! There are
1 x 10-23 moles of dogs running down the street!"
Could he be right for a change?
 Yes, 1 x 10-23 moles is:
1 x 10-23 moles x 6 x 1023 dogs per mole = 6 dogs.
If you like to solve problems with dimensional
analysis you would probably set this up as:
1 x 10-23 moles x 6 x 1023 dogs / 1 mole = 6 dogs.
volume?
shows a conversion
for volume.
volume
1 mole of any gas at
STP = 22.4 L
What’s STP?
STP means
standard
temperature and
pressure.
What’s STP?
Standard
temperature is 0° C
Standard pressure is
1 atm or 101.3 KPa
Find the volume that 24 g of
CO occupies at STP.

24 g     (1 mole)
( 28 g )
= 0.86 moles of CO
Find the volume that 24 g of
CO occupies at STP.

0.86 moles (22.4 L)
( 1 mol )
= 19.264 Liters
Find the number of atoms
in 24 g of CO

0.86 mol (6.02 x   1023)

(1 mol)
5.2 x  1023

molecules of CO
Find the density of one mole
of CO gas at STP.

Density = Mass
divided by volume
D = 28 g      =
22.4 L
Find the density of one mole
of CO gas at STP.

Density = Mass
divided by volume
D = 28 g      =   1. 25 g/L
22.4 L
Determine the percent composition
of Fe(OH)2

Fe – 1 x 55.8 = 55.8
O – 2 x 16 = 32
H–2x1= 2
Molar mass = 89.8
Divide element mass by molar
mass, then multiply by 100.

Fe – 55.8 x 100
89.8
O – 32 x 100
89.8
Divide element mass by molar
mass, then multiply by 100.

H –2 x 100
89.8
Percent compositions

% composition Fe = 62.1%
% composition 0 = 35.6%
% composition H = 2.2%
Add them up. Do they total
100?
Empirical formulas

Which of the following are
empirical formulas?
HCl
K2C2O4
Pb2O4
Empirical formulas

Only one is an empirical
formula.
HCl
The subscripts cannot
be reduced.
What is the difference
between a 6 M solution of
H2SO4 and a 1 M solution of
H2SO4 ?
The 6 M (molar) sulfuric
acid is much stronger. It
has 6 moles of the acid
dissolved in 1 liter of
solution. The 1 M has 1
mole dissolved in 1 liter.
So how many grams of
H2SO4 would you need to
make a 1 M solution?
A 1 M solution has 1 mole
dissolved in 1 liter so find
the molar mass of H2SO4
H 2x1=2
S 1 x 32 = 32
O 4 x 16 = 64
That totals 98 g.

A 1 M solution has 1 mole
dissolved in 1 liter so add
98 grams of H2SO4 to
almost one liter of water
water to make exactly 1 L.
So how many grams of HCl
would you need to make a 2 M
solution?
A 2 M solution has 2 moles
dissolved in 1 liter so find
the molar mass of HCl.
H 1
Cl 35.5
Total = 36.5 g
So how many grams of HCl
would you need to make a 2 M
solution?
A 2 M solution has 2 moles
dissolved in 1 liter so add
73 grams of HCl to almost
one liter of water then add
enough water to make exactly
one liter of solution.
This aqueous solution of HCl is
named hydrochloric acid!!!

A 2 M solution of HCl can
do some serious damage to
clothes and skin so beware.
Rinse immediately and put
baking soda on spills
ASAP.
 History of the Mole
The number of objects in one mole, that is,
6.02 x 1023, is commonly referred to as
an Italian physics professor who proposed in
1811 that equal volumes of different gases at
the same temperature contain equal numbers
of molecules.
 History of the Mole
About fifty years later, an Italian scientist named
to develop a set of atomic weights for the known
elements by comparing the masses of equal
volumes of gas. Building on this work, an Austrian
high school teacher named Josef Loschmidt
calculated the size of a molecule of air in 1865, and
thus developed an estimate for the number of
molecules in a given volume of air. While these
early estimates have since been refined, they led to
the concept of the mole - that is, the theory that in a
defined mass of an element (its atomic weight)
there is a precise number of atoms: Avogadro's
number.
 Molar Mass
A sample of any element with a mass equal to that
element's atomic weight (in grams) will contain
precisely one mole of atoms (6.02 x 1023
atoms). For example, helium has an atomic weight
of 4.00. Therefore, 4.00 grams of helium will
contain one mole of helium atoms. You can also
work with fractions (or multiples) of moles:
Mole challenge activity

 Do you know why the mole is an important
unit?
and solve a problem.
 The challenge: Using iron and sulfur, mass
out a number of grams of each that should
combine perfectly with no waste. Record
both masses.
Mole challenge activity

 Put chemicals together in a test tube.
 Use a magnet on the outside of the test tube to
move around the iron in the inside (just to show that
iron is magnetic).
 With a wooden splint or glass stirring rod, mix well.
 Using test tube holder and bunsen burner, heat the
chemicals until there is a chemical reaction.
Mole challenge activity

Using test tube holder and bunsen burner, heat the
chemicals until there is a chemical reaction.
Allow substance to cool.
Bring test tube to teacher who will evaluate the
product (FeS). If successful, there won’t be
anything magnetic (iron) or any sulfur leftover.
Only FeS should exist and that compound is NOT
magnetic. Test with a magnet. It may be necessary
to break the test tube to extract the substance. Your
teacher will do that for you. DON’T you break it.
How many moles of HCl
would you need to make
2 L of a 3M solution?
ext/intro/MOL.html

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