55 Counting Atoms with Coefficients
9/26/11
Counting Atoms with Coefficient 56
10/09/2014
10/09/2014
Starter:
How many atoms are in
.
the following compounds:
Connection:
Counting Atoms with
Coefficients Ws
H2O, NaCl, Cl2
Practice:
Chemical # of
Formula elements
NaCl
CO2
C6H12
HgOH
Ag2S
Li2O
Application
Paste Notes here
# of
atoms
Exit:
What is the difference
between a carbon dioxide
(CO2) and carbon monoxide
(CO)?.
October 09,2014
AGENDA
8.5 D.
I will be able to recognize
that chemical formulas
identify substances and
used to determine the
number of atoms of each
element in chemical
formulas by reading, and
writing while completing
notes and activity
1 Starter
2. Notes
3. Activity
4. Exit
NaCl
C2H4O2
Table of Contents
Date
Lecture/ Activity/ Lab
9/25
Test Review
9/29
Periodic Puzzles
9/30
Bohr Model Challenge
10/1
Wheres Al?
10/2
Element Wanted Poster
10/6
Molecules, Compounds, and Elements
10/07 Build a Molecule Activity
10/8
Counting Atoms
10/09 Counting Atoms with Coefficients
Page
39-40
41-42
43-44
45-46
47-48
49-50
51-52
53-54
55-56
Practice
Chemical
Formula
# of elements
NaCl
2
CO2
2
C6H12
2
2
3
18
HgOH
3
Ag2S
2
Li2O
# of atoms
2
3
3
3
Application:
Counting Atoms with
Coefficients
To determine the number of atoms
present,
MULTIPLY the subscript by the
coefficient
Example
3MgCl2
The coefficient for
this compound is 3
There are:
1 x 3 = 3 Mg
2 x 3 = 6 Cl
“Double” Subscripts
Sometimes ions have a “double” subscript
4Al(NO2)3
One subscript is INSIDE the
parenthesis and one subscript is
OUTSIDE the parenthesis
“Double” Subscripts
To count the number of atoms in a
compound with “double” subscripts, you
must MULTIPLY the subscripts
There are:
4Al2(CO2)3
This “2”
applies
only to
the O
This “3”
applies to
both C and O
2 x 4 = 8 Al atoms
3 x 1 x 4 = 12 C atoms
3 x 2 x 4 = 24 O atoms
Total atoms = 44
Example
5Mg(OH)2
The coefficient
for this
compound is 5
There are:
1 x 5 = 5 Mg2+ ions
2 x 1 x 5 = 10 O atoms
2 x 1 x 5 = 10 H atoms
Total atoms = 25
More Examples
1. How many of each atom in Ba3(PO4)2?
2. How many of each atom in 4Ba3(PO4)2?
3. How many of each atom in Al2(Cr2O7)3?
4. How many of each atom in 2Al2(Cr2O7)3?
Answers
1.
2.
3.
4.
3-Ba, 2-P, 8-0= 13
12-Ba, 8-P, 32-O= 52
2-Al, 6-Cr, 21-O= 29
4-Al, 12-Cr, 42-O= 58
55 Counting Atoms with Coefficients
9/26/11
Counting Atoms with Coefficient 56
10/09/2014
10/09/2014
Starter:
How many atoms are in
.
the following compounds:
Connection:
Counting Atoms with
Coefficients Ws
H2O, NaCl, Cl2
Practice:
Chemical # of
Formula elements
NaCl
CO2
C6H12
HgOH
Ag2S
Li2O
Application
Paste Notes here
# of
atoms
Exit:
What is the difference
between a carbon dioxide
(CO2) and carbon monoxide
(CO)?.