Percentage
Composition of
Substances

Daily Task
1.Calculate the percentage composition of a
substance given the chemical formula

3
How Do You Make Fireworks of Different Colors?
Two thousand years ago, a cook mixed three ingredients very
common in any kitchen: potassium nitrate (food preservative),
sulphur and charcoal. Mixed and and heated, they go off exploding
on a huge bang. This is basically gunpowder.
If this mixture is put on a cane, pressure builds up giving rise to a
bigger explosion. Originally, potassium nitrate was used.
Potassium cations are responsible of a white color. If different salts
are used instead, with different metals as cations, you get the
different colors. For example, strontium salts give red colors. Iron
compounds give gold-colored fireworks. Also, sodium gives yellow,
barium gives green and copper gives blue.

Why do you need to
know the nutritional
information provided
on the packaged food
labels?

What do you think
a chemist do when
he discovered a
new compound?
6

Percentage
Composition.
-the percentage by
mass of elements
present in a
compound.

Percentage
Composition requires
knowing the mass of
the entire
molecule/compound,
then the mass of its
components
8

% by mass= mass of element
mass of compound
x 100

Example: What are the percentage
composition of sodium and chlorine in
Sodium Chloride?
10
% Na= mass of Na
mass of NaCl
x 100
First,find the molar mass:
Mass of Na- 23 g/mol
Mass of Chlorine- 35 g/mol
_________________________
58 g/mol

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% Na= 23 g/mol
58 g/mol
=0.3965
x 100
x 100
=39.65 %
or 40 %
% Cl= 35 g/mol
58 g/mol
=
% Na= 23 g/mol
58 g/mol
=0.3965
x 100 100
x
0.603 % or
60 %

For both plants and humans, glucose is like
the fuel for a machine. Plants produce
sugar in their leaves in the form of
glucose C6H12O6
Determine the percentage
composition of glucose C6H12O6

.
The experiment conducted by
Henry Mosely on the
radioactive emissions of
elements, found a way of
counting the number of protons.
atomic number-equal to the number of
protons of an element
-expressed as Z
-identifies an element,also equal to # of
electron

.
mass number-combined number of
protons and neutrons
-expressed as A.
Mass # - proton= neutron

.

Atoms, in their
most stable
state are
neutral with an
equal number
of protons
and electrons.
Something to think
about
So, let us say an
atom has 5
electrons, how
many protons
does this atom
have?

One more time:
How about if the atom has 64
protons, how many electrons
does this atom have?

One more time:
# of protons=
# of electrons=
# of neutrons=
Atomic #=
Mass number # =

Check Up
Quiz (4)
On your notebook, answer the
following:

Enumeration
1-9 List the 3
subparticles of an atom
with their charges and
location, (in or outside
the nucleus)
10. If a neutral atom
has 4 electrons, how
many protons are there?

True or False
11. A neutral atom has a negative one
charge.
12. In a neutral atom, if there are 6
electrons there are also 6 protons.
13. A table, a chair, a sweater contain
charges.
14. Electrons are transferred when a
material is rubbed with another material
and this is called static electricity.
15. When a negative charged object is
put near to a positive charged object, the
two objects will repel.
21

Maps
our office
22

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Whoa! That’s a big number, aren’t you proud?
23

89,526,124$
That’s a lot of money
100%
Total success!
185,244 users
And a lot of users
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Our process is
easy
first second last
25

Let’s review some
concepts
Yellow
Is the color of gold, butter
and ripe lemons. In the
spectrum of visible light,
yellow is found between
green and orange.
Blue
Is the colour of the clear
sky and the deep sea. It is
located between violet
and green on the optical
spectrum.
Red
Is the color of blood, and
because of this it has
historically been
associated with sacrifice,
danger and courage.
26
Yellow
Is the color of gold, butter
and ripe lemons. In the
spectrum of visible light,
yellow is found between
green and orange.
Blue
Is the colour of the clear
sky and the deep sea. It is
located between violet
and green on the optical
spectrum.
Red
Is the color of blood, and
because of this it has
historically been
associated with sacrifice,
danger and courage.

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Thanks!
Any questions?
You can find me at:
@username
user@mail.me
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