Transcript Stoichiometry and Gases

Stoichiometry and Gases
By: Carson Ram & Thomas Schweinfurth
The Periodic Table
Atomic Number:
Representative of the
protons
Atomic Symbol:
Letter representation
of the element
Atomic Weight:
Representative the neutrons &
protons
The Periodic Table
Family:
Down a
column
1A: Alkaline
2A: Alkaline
Earth Metals
C
h
a
l
c
o
g
e
n
s
H
a
l
o
g
e
n
s
8A:
Noble
Gases
Period:
Across a
row
Metals
Metalloids
Nonmetals
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Atoms, Molecules, and Ions
• Molecular Formulas: Indicate the actual
numbers and types of atoms in a molecule
• Empirical Formulas: Give only the relative
number of atoms of each type in a molecule
• Example…
Molecular Formula
C2H4
Empirical Formula
CH2
Chemical Nomenclature
• Tips & Tricks for naming cations:
– Cations formed from metal atoms have the same
name as the metal:
• Ex. Ca+2  calcium ion
– If a metal can form different ions, the positive charge
is indicated by a Roman numeral in parenthesis
behind the name of the metal:
• Ex. Fe2+  iron (II) ion
Fe3+ iron (III) ion
– Cations formed from nonmetal atoms have names
that end in –ium:
• NH4+ammon-ium ion
H3O+ hydron-ium ion
Chemical Nomenclature
• Tips & Tricks for naming anions: (Part One)
– The names of monatomic anions are formed by
replacing the ending of the name of the element
with –ide:
• Ex. Br- Brom-ide Ion
Cl-Chlor-ide Ion
– Polyatomic anions containing oxygen have names
ending in –ate or –ite.
• Ex. NO3-  Nitr-ate Ion
NO2-  Nitr-ite Ion
– The Prefix per- indicates one more atom than the
ion ending in –ate.
– The Prefix hypo- indicates one fewer atom than
the ion ending in –ites.
Chemical Nomenclature
• Tips & Tricks for naming anions: (Part Two)
– Anions derived by adding H+ to any oxyanion are
named by adding as a prefix the word hydrogen or
dihydrogen, as appropriate.
•
•
•
•
Ex.
PO43-  phosphate
HPO42-  hydrogen phosphate
H2PO4-  dihydrogen phosphate
– Names of ionic compounds consist of the cation
name followed by the anion name
• Ex. NaCl  Sodium Chloride
Structuring
A : Mass Number
Z : Atomic Number
Q : The Charge
Percentage Compostitions
Formula Weight: Sum of the atomic weights of each atom in its chemical formula.
Example:
Calculate the percentage of carbon in C12H22O11.
Atomic Weight of Carbon:
12.0 amu
Addition of Atomic Weights:
12 C atoms = 12 (12.0 amu) = 144.0 amu
22 H atoms = 22 (1.0 amu) = 22.0 amu
11 O atoms = 11 (16.0 amu) = 176.0 amu
342.0 amu
Avogadro’s Number
• Named after Amedeo Avogadro (1776-1856)
• NA = 6.02 x 1023 atoms / 1 mol
• 1 mol ‘Element’ = 6.02 x 1023 atoms
• 1 mol ‘Compound’ = 6.02 x 1023 molecules
• 1 mol ‘Ions’ = 6.02 x 1023 ions
Limiting Reactants
• Limiting Reagent: Determines, or limits, the
amount of product formed.
• Left over reactants are often called excess
reactants.
• Theoretical Yield: Quantity of product
calculated to form
• Actual Yield: Quantity of product actually
obtained
Gases
• Standard temperature and pressure (STP) is 273.15 K
and 1 atm.
– 1 atm = 760 mm Hg = 760 torr = 101.325 kPa
• Boyle’s Law: States that the volume of a fixed
quantity of gas maintained at constant temperature
is inversely proportional to the pressure.
– PV = constant
• Charles’s Law: States that the volume of a fixed
quantity of gas maintained at a constant pressure is
directly proportional to the absolute temperature.
– V / T = constant
Gases
• Avogadro’s Hypothesis: Equal volumes of
gases at the same temperature and pressure
contain equal numbers of molecules.
• Avogadro’s Law: states that the volume of a
gas maintained at constant temperature and
pressure is directly proportional to the
number of moles in the gas.
– V / n = constant
Ideal Gas Law
• The ideal-gas equation is… PV = nRT.
• R is the gas constant.
– R=8.314 J/molK
R=0.08206 Latm/molK
• Remember! Temperature is in Kelvins, not
degrees Celsius.
More About Gases
• If n and T are constant, the values of P and V
can change, but the product of PV must
remain constant, so:
– P1V1=P2V2
• When just n is constant, P,V, and T can all
change but the product of (PV)/T must remain
constant so:
– (P1V1)/T1=(P2V2)/T2  Often called the combined
gas law
Partial Pressure
• The total pressure of a mixture of gases equals
the sum of the pressures that each would
exert if it were present alone:
– Pt = P1+P2+P3
• Each gas in a mixture behaves independently
so we can relate the amount of a given gas in
a mixture to its partial pressure:
– P1 / Pt = (n1RT/V) / (ntRT/V) = n1/nt mole fraction
– P1=(n1/nt )Pt
Graham’s Law and rms Speed
• Particles with lighter masses have a higher rms
speed.
– u=
3RT
M
M is molar mass
• Graham’s law states that if we have two gases
at the same temperature and pressure in
containers with identical pinholes, and r is the
rate of diffusion, then:
– r1/r2=
( M 1)
( M 2)
Van der Waals
• Van der Waals recognized that the ideal gas
equation could be corrected to account for
the effects of attractive forces between gas
molecules and for molecular volumes.
• Constant a is a measure of how strongly the
gas molecules attract each other and constant
b is a measure of the small but finite volume
occupied by the gas molecules themselves.
• (P+(n2a)/V2)(V-nb)=nRT
Thanks to…
Chemistry: The Central Science by T. Brown, H.
LeMay, B. Bursten, and C. Murphy