Transcript 2 KClO 3

Types of nuclear processes
Atoms can eject protons or helium nuclei & get lighter.
They can swallow a neutron & spit out the proton to get heavier.
Whenever the # of protons changes, the atom type has changed.
Figure 5.6 Uranium Decay Path
Where does a 900-pound gorilla sit?
When does radioactive decay occur?
Decay events—e.g. electrons detected
for beta decay—most probable at first
As radioactive molecules become
depleted, detected events decrease.
Announcement Break
Monday, November 5
I am baaaack! Should be available thru Wednesday.
Chapter 8 notes posted
Chapter 8 Personal Responsibility Problems Posted
There are a LOT of problems here….’cuz it really matters.
Average on Ex4: 53% (hey, it’s double the guess score!)
High: 90%
That was a hard test if you aren’t doing PRP’s.
Moral of this story
•Do not smoke
•Insecticides can ignite
•Requires spark
•Gives off energy
•You have to be careful with
chemistry
Time to do REAL
chemistry:
Starting Chapter 8
Stuff All Chemists Must Know:
•Conservation of Numbers: in a chemical rxn, atoms aren't
changed, lost or made.
•Same true of electrons, protons & neutrons.
•Conservation of Mass: mass isn't gained or lost either
(neglecting those tiny losses in nuclear reactions).
•Chemistry goes by integer numbers -- albeit rather large
integers in most cases.
Zillions
C + O  CO
We think: one atom at a time.
Reality: zillions of C’s, zillions of O’s,
zillion’s of CO’s
Practice with sub-Zillion Numbers
One dozen cookies = 12 cookies
Two dozen eyes = 24 eyes
Four dozen yellow frosting zones =
= 48 squeezes of yellow frosting tube.
Other convenient numbers: Baker’s dozen = 13
Gross = dozen dozen = 144
The mole: chemist’s dozen
Avogadro's number
= 602202035873921029561369
= 6.02202035873921029561369 x 1023
This is a lie!!!!
Atomic Mass Unit: where Avogadro's
number comes from.
•Earlier we said "Let one atom of H have 1 atomic mass unit"
•Now, we have a problem, because H has 3 isotopes:
•So.....we cannot use "hydrogen" as it usually exists (mixed
isotopes) for our mass standard.
•We must purify it.
•Easier to purify carbon, so carbon became the mass standard:
Atomic mass unit:
1 a.m.u. = 1/12th the mass of isotope
A single atom of
= 1.660 x 10-24 g.
weighs 12 x 1.660 x 10-24 g.
Avogadro’s Number:
inverse of a.m.u.
How many atoms of are in 12.000 grams
of pure isotope
Answer: (12 grams of
(
)
)
1 atom
12 x 1.660 x 10-24 grams
= 6.022 x 1023 atoms
It’s the same as the number of atoms of hydrogen in one gram
of hydrogen (assuming only the “normal” hydrogen isotope).
Avogadro’s Number: Fixing that Lie
We said: 602202035873921029561369
6.02202035873921029561369 x 1023
We really only know the first few numbers, so:
6.022 x 1023
Why did I fib?
To emphasize that Avogadro’s number is an integer, just as a
dozen or a gross are integer numbers. All the things we do
with ordinary integer numbers we also do with Avogadro’s
number. Compare the national debt, another “big” number:
The Outstanding Public Debt as of
05 Nov 2001 at 07:26:45 PM GMT is:
Your share: $20,259.19
Irrelevance of Detail
Wouldn’t $5.78 x 1012 be close enough?
Your share: $2.0 x 104 = $20,000
Compound Formula and
Molecular Weights
Molecular weight: how many a.m.u. per molecule
(same as how many grams per 6.022x1023 molecules)
Formula weight: how many a.m.u. per formula
(same as how many grams per 6.022x1023 repeats of the formula)
Get Molecular weight:
Example in notes: CH4
Example here: benzene, C6H6
Get Formula weight for :
Ba(HCO3)2
How many carbon atoms in 7.8
grams of benzene, C6H6
How many hydrogen atoms?
Comparable automobile problem
1965 Plymouth Barracuda’s weigh 3,000 pounds.
How many tires per 9,000 pounds of Fishcar?
Answer: 12 (not counting the spare)
How many cubic inches per 9,000 pounds of Fishcar?
3 x 273 = 819 cubes
How many horsepower per 9,000 pounds of Fishcar?
No one knows! About 750 (3 x 250)
Question:
Which is potentially worth more?
1000 g of AgCl
or.....
1000 g of AgI
or.....
1000 g of Ag NO3 ?
or.....
500 g of Ag2CO3
Let's do another, perhaps a bit harder.
1. What is molecular mass of penicillin, C16H17N2O5SK
2. What is mass of 0.45 mol of penicillin?
3. How many C atoms in 19.5 g of penicillin?
4. What percentage of penicillin, by weight, is oxygen?
Actually, I don’t think this
is pencillin—maybe a derivative.
Dorothy Crowfoot Hodgkin, Nobel Prize 1964
Reactions
CH4 + O2 ---» CO2 + H2O
Unbalanced: a list of ingredients & results
CH4 + 2O2 ---» CO2 + 2H2O
Balanced: a correct recipe
Wheels + Pedals + Handlebar ---» Bicycle
Unbalanced: a list of ingredients & results
2 Wheels + 2 Pedals + 1 Handlebar ---» Bicycle
Balanced: a correct recipe
Blazing Bubbles
Chemical Equivalence: d
The d symbol defines the relation between two compounds
according to the particular balanced chemical reaction being
considered!
It acts like a conversion factor!
Consider: 2 KClO3 ----» 2 KCl + 3 O2
2 KClO3 d 2 KCl which is the same as: 1 KClO3 d 1 KCl
This simply means that one KCl will be produced for every
KClO3 present in this reaction (other reactions that produce
KCl will be different).
More about Chemical Equivalence: d
2 KClO3 ----» 2 KCl + 3 O2
KClO3: 122.45 g/mol
KCl: 74.45 g/mol
O2: 32 g/mol
74.54 g of KCl d 122.45 g of KClO3
We can also write: 2 KClO3 d 3 O2
Or: 244.9 g KClO3 d 96 g O2
This means we get 96 g of oxygen for every 244.9 g of KClO3.
Chemical Equivalence in Use
How much oxygen can we get from 100 g of KClO3?
96 gO2
100 gKClO3 
 39.2 gO2
244.9 gKClO3
Another question on the same theme:
How much KClO3 will I need to
produce 1 ton of O2?
Another Example (more complex, but
also more fun....and a little depressing!)
How many tons of CO2 are produced by
burning 1000 gallons of gasoline?
Assume density of gasoline is 0.692 g/ml
and formula is C8H18.