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Chapter 10Chapter 10“Chemical Quantities”“Chemical Quantities”
You will need a calculator for this
chapter!
Section 10.1 p. 287Section 10.1 p. 287The Mole: A Measurement The Mole: A Measurement
of Matterof Matter
How do we measure items?How do we measure items?You can measure mass, volume,or count pieces
We measure mass in gramsWe measure volume in litersWe count pieces in MOLES
Other Ways to Measure Other Ways to Measure AmountAmount
Pair: 1 pair of socks = 2 socks Dozen: 1 dozen donuts = 12 donuts Gross: 1 gross of pencils = 144
pencils (12 dozen) Ream: 1 ream of paper = 500
sheets of paperGuided Practice Problem p. 289
Practice Problem #2 Practice Problem #2 pg. 289pg. 289
• Assume 2.0 kg of apples is 1 dozen and that each apple has 8 seeds. How many apple seeds are in 14 kg of apples? (work INDEPENDENTLY to solve)
What is the mole?
Not this kind of mole!
Moles (abbreviated Moles (abbreviated molmol))Derived from German word molekül (molecule)
SI measurement of an amount 1 mole = 6.02 x 1023 of representative particles, or…..
# of carbon atoms in exactly 12 g of Carbon-12 isotope
Called Avogadro’s numberAvogadro’s number
What are Representative Particles?What are Representative Particles?
(Table 10.1 p. 290)(Table 10.1 p. 290) The smallest pieces of a
substance:1) molecular cmpd - molecule2) ionic cmpd - formula unit (made
of ions)3) element: is the
• Remember the 7 diatomic elements? (made of molecules) BrINClHOFH2
N2 O2 F2Cl2
I2Br2
atoatomm
Guided Practice Problem #3 p. 291
Mole Video 3:49
Quick QuizQuick Quiz• How big is a mole?• If everyone in the world got a mole of
pennies, how much $ would every person have?
• If you stacked a mole of paper how many times would it go from the Earth to the moon?
• How long would it take for every person in the world to eat through a mole of marshmellows?
6.02 x 6.02 x 10102323
1 trillion bucks1 trillion bucks$1,000,000,000,000$1,000,000,000,000
80 billion 80 billion timestimes80,000,000,00080,000,000,000
40,000,000 years w/o 40,000,000 years w/o a bathroom break!a bathroom break!
Consider these questions:Consider these questions:• How many oxygen atoms in
the following?CaCO3
Al2(SO4)3
• How many ions in the following?CaCl2NaOHAl2(SO4)3
3 atoms of oxygen
12 (3 x 4) atoms of oxygen
3 total ions (1 Ca2+ ion and 2 Cl1- ions)
2 total ions (1 Na1+ ion and 1 OH1- ion)
5 total ions (2 Al3+ + 3 SO42- ions)
Practice problemsPractice problems
The Mass of a Mole of an The Mass of a Mole of an ElementElement
Atomic mass of element (mass of 1 atom) expressed in amu- atomic masses - relative masses based on mass of C-12 (12.0 amu)
- 1 amu is 1/12 mass of C-12 atom
Molar Mass…. Molar Mass…. = mass of 1 mol of element in in
gramsgrams (periodic table) 12.01 grams C has same #
particles as 1.01 g H & 55.85 g Fe 12.01 g C = 1 mol C 1.01 g H = 1 mol H 55.85 g Fe = 1 mol Fe
All All contain contain 6.02 x 6.02 x 10102323 atomsatoms
Molar Mass Practice Molar Mass Practice ProblemsProblems
What about compounds?What about compounds? 1 mol of H2O molecules has 2
mol of H atoms & 1 mol of O atoms (think of a compound as a molar ratio)
To find mass of 1 mol of a cmpd: odetermine # moles of elements presentoMultiply # times their mass (from periodic table)oadd up for total mass
Calculating Molar MassCalculating Molar Mass
Calculate molar mass of magnesium carbonate, MgCO3.
24.3 g + 12.0 g + 3 x (16.00 g) = 84.3 g
So, 84.3 g = molar mass for MgCO3
Section 10.2 Section 10.2 p. 297p. 297
Mole-Mass and Mole-Mole-Mass and Mole-Volume RelationshipsVolume Relationships
Molar MassMolar MassMolar mass - generic term for
mass of 1 mol of any substance (expressed in grams/mol)
Same as: 1) Gram Molecular Mass (for molecules)
2) Gram Formula Mass (ionic
compounds) 3) Gram Atomic Mass (for elements)
o molar mass is more broad term than these other specific masses
ExamplesExamples Calculate the molar mass of:Na2S
N2O4
C Ca(NO3)2
C6H12O6
(NH4)3PO4
= 78.05 g/mol
= 92.02 g/mol
= 12.01 g/mol
= 164.10 g/mol
= 180.12 g/mol
= 149.12 g/mol
Molar Mass is…Molar Mass is…# of g in 1 mol of atoms, formula units, or molecules
Make conversion factors from these- To change btwn g of cmpd and mol of cmpd
Using the Mole RoadmapUsing the Mole RoadmapHow many moles is 5.69 g of NaOH?0.142 mol NaOH
The Mole-Volume RelationshipThe Mole-Volume Relationshipgases
- hard to determine masshow many moles of gas?2 things affect gas V:
a) Temp & b) Pressurecompare all gases at = temp & pressure
Standard Temperature and PressureStandard Temperature and Pressure 0ºC & 1 atm pressure
- abbreviated “STP” At STP, 1 mol of anyany gas has V of 22.4 L- Called molar volume
1 mol of any gas at STP = 22.4 L
Practice ExamplesPractice Examples
Mole DayCelebrated on October 23rd from 6:02 am until 6:02 pm(6:02 on 10-23)
Density of a gasDensity of a gas D = m / V (density = mass/volume)- for gas units are: g / L
find density of a gas at STP if formula known
You need: 1) mass and 2) volume Assume 1 mol, so mass is molar mass (from periodic table)
At STP, V = 22.4 L
Practice Examples Practice Examples (D=m/V)(D=m/V)
Another way:Another way: If given densityIf given density, find molar mass
of gas Assume 1 mol at STP, so V = 22.4 L
modify: D = m/V to show: “m” will be mass of 1 mol, given
22.4 L What is molar mass of a gas with
density of 1.964 g/L? How about a density of 2.86 g/L?
= 44.0 g/mol
64.0 g/mol
m = D x V
SummarySummary• all equal:all equal:
a) 1 moleb) molar mass (in grams/mol)c) 6.02 x 1023 representative particles (atoms, molecules, or formula units)
d) 22.4 L of gas at STPmake conversion factors from these 4 values (p.303)
Notice all conversions Notice all conversions must go through the must go through the
MOLE!MOLE!Copy this conversion Copy this conversion map into your notes!map into your notes!
Section 10.3Section 10.3p. 305p. 305
Percent Composition Percent Composition and Chemical and Chemical
FormulasFormulas
All percent problems: part whole
1)1) Find mass of each element,Find mass of each element,
2)2) Divide by total mass of cmpd; & x Divide by total mass of cmpd; & x 100100
x 100 % = percent
%mass of element = mass of element
x 100% mass of cmpd
% composition from mass% composition from mass Calculate the percent
composition of a compound that is made of 29.0 grams of Ag with 4.30 grams of S.
29.0 g Ag33.3 g total
X 100 = 87.1 % Ag
4.30 g S33.3 g total
X 100 = 12.9 % S
Total = 100 %
% comp from the chemical formula% comp from the chemical formula If we know formula, assume
you have 1 mole, Subscripts used to calculate
mass of each element in 1 mole of cmpd
sum of masses is molar mass
% Composition Examples% Composition Examples
% composition as % composition as conversion factorconversion factor
We can also use % as conversion factor conversion factor to calculate # grams of element in cmpd
Calculate % C in Calculate % C in C3H8
What is mass of C in 82.0 g sample of propane (C3H8)
67.1 g C
% Composition% Composition4:15
What is an Empirical Formula?What is an Empirical Formula?• Like ingredients for recipe –
double recipe, you double each ingredient, but ratioratio of ingredients stays same
• Empirical formula: lowest whole number ratio of atoms in cmpd
Calculating EmpiricalCalculating EmpiricalFind lowest whole number ratio
C6H12O6
CH4NA formula is not just ratio of
atomsatoms, it is also ratio of moles1 moleculemolecule of CO2 = 1 atom of C atom of C and 2 atoms of O 2 atoms of O
1 mol of CO2 = 1 mol C and 2 mol O
= CH2O
= this is already the lowest ratio.
Calculating EmpiricalCalculating Empirical get a ratio from % composition1)Assume you have a 100 g
sample- the percentagepercentage become gramsgrams (75.1%75.1% = 75.1 75.1
gramsgrams)
2) Convert gramsgrams to molesmoles. 3) Find lowest whole number ratio
by dividing each # of molesmoles by smallest value
ExampleExampleCalculate empirical formula of cmpd composed of 38.67 % C, 16.22 % H, and 45.11 %N.
Assume 100 g sample, so 38.67 g C x 1mol C = 3.22 mole C
12.0 g C 16.22 g H x 1mol H = 16.22 mole
H 1.0 g H 45.11 g N x 1mol N = 3.22 mole
N 14.0 g N
Now divide each value by the smallest value
CH5N
ExampleExample The ratio is 3.22 mol C = 1 mol C
3.22 mol N 1 mol N
The ratio is 16.22 mol H = 5 mol H 3.22 mol N 1 mol
N
= C1H5N1 which is = CH5N
Practice Problem 36 p. 310Practice Problem 36 p. 310
What is a Molecular Formula?What is a Molecular Formula?• Molecular formula: true # of atoms of
each element in formula of cmpd
• molecular cmpds only• Example: molecular formula for
benzene is C6H6 (note that everything is divisible by 6) • Therefore, empirical formula =
CH (the lowest whole number ratio)
FormulasFormulas (continued)(continued)
ionic compoundsionic compounds ALWAYS empirical (cannot be reduced).
Examples:
NaCl MgCl2 Al2(SO4)3 K2CO3
FormulasFormulas (continued)(continued)
Formulas for molecular compoundsmolecular compounds
MIGHT be empirical (lowest whole number ratio).
Molecular:
H2O
C6H12O6 C12H22O11
Empirical:
H2O
CH2O C12H22O11
(Correct formula)
(Lowest whole number ratio)
Empirical to molecularEmpirical to molecularSince empirical formula is lowest ratio, the actual molecule weighs more
Molar mass
Empirical formula masswhole # to increase each coefficient in empirical formula
=
Empirical to molecular Empirical to molecular practice problempractice problem
Empirical and Empirical and Molecular FormulasMolecular Formulas
3:29