Chemistry Flashcards Template Page 10
ADVERTISEMENT
1
2
3
4
5
6
7
8
9
10
11
12
13Working Backwards
Percent Composition
Chemical formula
An unknown compound is analyzed (see later) and determined to
Pretty easy (after some practise) to get the
be 57.84 % C, 3.64 % H and 38.52% O (by mass). Can you
percent composition from a known molecular
determine the compound’s molecular formula ? See text 109-114.
formula.
For compound C
H
O
x
y
z
⎛
⎞
⎛
⎞
⎛
⎞
M
M
M
%C
%H
%O
C H O
C H O
C H O
⎜
⎟
⎜
⎟
⎜
⎟
x
y
z
x
y
z
x
y
z
x =
; y =
; z =
⎜
⎟
⎜
⎟
⎜
⎟
100%
M
100%
M
100%
M
⎝
⎠
⎝
⎠
⎝
⎠
Can you work backwards to get the
C
H
O
molecular formula if you know the percent
composition ?
Chemical Composition
Chemical Composition
Combustion Analysis
How percent composition is determined experimentally
Smallest coefficient
Divide equations (1), (2) and (3) by equation (3)
C
H
O
= C
H
O
The result is the empirical formula
x
y
z
4
3
Chemical Composition
Chemical Composition
10
ADVERTISEMENT
0 votes
Related Articles
Related forms
Related Categories
Parent category: Life