Basic mole-mass-count

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The road trip through mole land so far

• Basic mole-mass-count
• conversions ( divide up,
• multiply down)
• Mole ratio conversion within
• a compound (body parts relationships)

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The mole road ahead...

• composition problems
• and combustion analysis
• (pp. 94-103)
• moles level 2b
• Reaction balancing
• (pp. 105-108)
• Reaction stoichiometry predictions, limiting
  yields and yields ( pp. 108-123) moles level 3

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Why bother with all of this ????
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stoichiometric studies in the 18th and 19th
century are foundation to things like
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Doped semiconductors
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Combustion analysis
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Combustion analysis also leads to
Optical fiber
Without which there is no.
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composition problems using mole concept to
convert weights to formulas
Sample composition problem 1
A compound of N and O contains 63.63 wt N and
36.36 wt O. What is the empiric formula of the
compound ?
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Definition
empiric formula mole ratio of elements in a
compound expressed in lowest whole numbers
Example CH2O empiric formula of glucose (sugar
we metabolize)
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Empiric formulas (continued)
CH2O empiric formula of glucose (sugar we
metabolize)
Actual molecular formula (what it really has in
atom count)
(CH2O)6
C6H12O6
Sugar Carbo hydrate
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Which formulas below are empiric ( lowest
common denominator form) ??
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NOT EMPIRIC
EMPIRIC
C3H6O3
CH2O
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Which formulas below are empiric (continued) ??
EMPIRIC3 7 have no shared factors
N3F7
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Which formulas below are empiric (continued) ??
H3P9O12S5
EMPIRIC (3,9,12 divisible by 3but 5 is not)
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composition Problem 1 empiric formula
determination
A compound of N and O contains 63.63 N and 36.36
O. What is the empiric formula of the compound?
lets do it on the board
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Sample problem 1 SUMMARIZED
OFFICIAL NAME
Dinitrogen monoxide
gtN2O
Laughing gas
n nmin
element
N
O
AWAtomic wt (g/mol)
nw/AW moles
w(g)
4.545 2 2.273
63.63/14 4.545
63.63
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36.36/16 2.273
2.273 1 2.273
36.36
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Joseph Priestley 1772
http//www.youtube.com/watch?v_Ha-ZrUPJ_E
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An oxide of nitrogen contains 46.7 wt. N and
53.3 O. What is its empiric formula ?

1. NO3
2. NO2
3. N2O
4. N3O7
5. NO
6. None of the above

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composition Problem 3 empiric molecular
formula determination
The previous empiric compound (C2H4O3) has a
molecular weight of 228 g/mol. What is the
molecular formula of the compound ?
Lets do this on the board
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composition Problem 4 empiric formula
determination with a twist
A compound composed of C,H and O is 48.64 C and
8.16 H and 43.2 O by mass. What is the
empiric formula ?
Answer C1.5H3O1? C3H6O2
element Mass,g Atomic wt(g/mol) nmass Atomic wt n/nmin
C 48.64 12
H 8.16 1
O 43.2 16
x FACTOR
1.52 3
48.64/12 4.05
4.05/2.7 1.5 ?
8.16/1 8.16
3.02 6
8.16/2.7 3.0
43.2/16 2.70
2.7/2.7 1
12 3