Mr Guerrero Stoichiometry Homework due on the day of chapter exam Zumdahl Text 9 th ed page 126 10 13 18 38 40 46 50 66 74 84 86 88 100 106 122 124 126 Write out all conceptualnonmath questions amp answer in complete sentences ID: 742585
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Slide1
Stoichiometry AP ChemistryMr. GuerreroSlide2
Stoichiometry Homework, due on the day of chapter exam. Zumdahl
Text, 9
th
ed.
page 126:
#10, 13, 18, 38, 40, 46, 50, 66, 74, 84, 86, 88, 100, 106, 122, 124, 126.
Write out all conceptual(non-math) questions & answer in complete sentences.
Box all answers.
Math questions: write out all givens and unknown. Show all work, you do not need to write out these questions.Slide3
IsotopesElement-matter consisting of atoms with the same # of protons. Isotopes- atoms of the same element w/ different # of neutrons.
Most elements are comprised of several isotopes.
Ex: Boron, B-10(10.0129
amu
, 19.80%) & B-11(11.009amu, 80.20%)Slide4
Finding avg atomic mass from isotope abundancies
Find the avg. atomic mass of boron as an element.
AVG. = M
1
F
1
+ M
2
F
2
+ …..
M
1
mass of 1
st
isotope, F
1
fraction of 1
st
isotope=%/100
M
2
mass of 2
nd
isotope, F
2
fraction of 2
nd
isotope=%/100Slide5
BoronB-10(10.0129
amu
, 19.80%) & B-11(11.009amu, 80.20%)
What is the avg. atomic mass of boron?Slide6
Isotope practiceCopper has two natural occurring isotopes:
Cu-63(62.9296
amu
) 69.17% & Cu- 65. What is
the atomic mass of the Cu-65 isotope? Slide7
AntimonySb-121(120.9038 amu
) & Sb-123(122.9042
amu
)
Find the relative abundancy of each isotope:Slide8
Old Pennies/New PenniesOld pennies = 3.07g & New pennies = 2.49g
If 10 pennies have a mass of 26.65 grams, how many
old pennies are in the mix?Slide9
Mass Spectrometer-an instrument that vaporizes, then ionizes a sample. It is then accelerated across a magnetic field. The momentum of the particles determines it’s angle of deflection. The angle determines the atomic mass of the particles.Slide10
Calculate the avg. atomic mass & identify the element:Slide11
Calc. the avg. atomic massSlide12
Calc. the avg. atomic mass:Slide13
One more time…..Iridium has two naturally occurring isotopes: Ir-191(190.9606amu) & Ir-193(192.9629amu) Find the relative percent abundance of each isotope.Slide14
Molar massMolar mass- the mass of 1 mole of substance.1mole= 6.022 x 10
23
particles
What is the molar mass of each?
N
2
(g)
P
4
(s)
O
3
(g)
S
8
(s)
C
(soot)
C
60
(s)
C
6
H
12
O
6
(s)
Mg
3
(PO
4
)
2
(s)
Slide15
Every pure substance has a formula:Molecular Formula- (true formula) the actual # of atoms in a molecule.
Empirical Formula-the Molecular formula in simplest whole number ratio.
Substance Molecular F. Empirical F.
glucose C
6
H
12
O
6
CH
2
O
water H
2
O
H
2
O
butane C
4
H
10
C
2
H
5Slide16
Percent Composition Empirical Formula
A mass spectrometer is a machine that finds the % of each element in a compound. From the experiment results, we can easily find the formula of unknown substances.Slide17
Ex: An experiment yields that a substance is 43.64% phosphorus, and the rest is oxygen.The molar mass is 284 g/mol. Find the empirical and molecular formulas.Slide18
A substance is found to be 49.99%C, 5.61%H, and the rest is oxygen. Find the empirical & molecular formulas, if the molar mass is 216g/mol.Slide19
Empirical FormulaPercent Composition
Find the percent composition of each:
CO
2
Al
2
O
3
Fe
2
O
3
Fe(NO
3
)
3Slide20
20 min. Quiz tomorrowSlide21
Reaction stoichiometry
Law of conservation of mass-during an ordinary chemical reaction, matter is neither created, nor destroyed.
During a chemical reaction, atoms change the way that they are bonded, but they are still the same atoms. Ergo, the mass of all reactants must equal the mass of all products.
For this reason, we must balance chemical equations.Slide22
Balance the following reactions
TYPE of
Rxn
C
5
H
10
+ O
2
CO
2
+ H
2
O
N
2
+ H
2
NH
3
NO
2
N
2
O
4
H
2
O
2
H
2
O + O
2
K
2
CO
3
+ Ca CaCO
3
+ K
Na
3
PO
4
+ CuSO
4
Cu
3
(PO
4
)
2
+ Na
2
SO
4
Slide23
Molar ConversionsX is always the given substance:
Grams X
Mole X
Moles Y
Grams Y
Particles X
Liters X(@STP)
Particles Y
Liters Y(@STP)Slide24
Molar Conversions practice:If 45.8 grams of ammonia reacts with excess oxygen, how many grams of H2
O can form?
Rxn
: NH
3
+ O
2
NO + H
2
OSlide25
If 16.3 liter of oxygen gas(@STP) react with excess C3H6, how many CO2
molecules can form(assuming 100% yield)?
Rxn
: C
3
H
6
+ O
2
CO
2
+ H
2
OSlide26
Percent Yield3.50 grams of H2 react with excess O
2
, to form 30.8 grams of water. Find the percent yield.
Slide27
Percent Yield2.8 moles N2 react with excess H
2
. How much NH
3
will form at 88.5 percent yield?Slide28
Limiting ReactantLimiting Reactant-the reactant which runs out first, ending the reaction.Excess Reactant-reactant that has
unreacted
amount left over.Slide29
If 14.5 liters NH3 gas(@STP) react with 50.0 gramsCuO(s)
, how many grams of H
2
O can form? Find the
Limiting reactant and the amount of excess left over.
Rxn
: NH
3(g)
+
CuO
(s)
N
2(g)
+ Cu
(s)
+ H
2
O
(g)Slide30
If 5.00 x 1023 Fe3O4
formula units react with 98.2 liters CO(@STP). How many grams CO
2
can form? Identify the LR/ER. How much excess is left over?
Rxn
: Fe
3
O
4
+
4
CO
3
Fe +
4
CO
2
Slide31
25.0 grams of C3H8 react with 25.0 grams of O
2
. What mass of H
2
O can form? Identify LR/ER & amount left over.
C
3
H
8
+
5
O
2
3
CO
2
+
4
H
2
OSlide32
Combustion Analysis: Determining the formula of a compound by mass of CO2 & H2O formed.Slide33
A 0.00300 g sample of napthalene, a compound containing only carbon and hydrogen, was burned in excess oxygen to give 0.0103 g of CO
2
. Determine the empirical formula of
napthalene
. The formula weight (molecular weight) of
napthalene
is 128 u, determine the molecular formula.Slide34
Combustion Analysis: Determining the formula of a compound by mass of CO2 & H2O formed
.
Menthol contains carbon, hydrogen and oxygen, 95.6
mg of menthol (molar mass = 156 g/
mol
) are burned in oxygen gas to give 269 mg CO
2
and 110 mg H
2
O. What is menthol's empirical
and molecular formula
?