Download slides

Unit 1: Stoichiometry and
Gases
By Alex and Maria
Tour of the Periodic Table
– Groups and Periods
• Groups: vertical columns
of elements with similar
chemical and physical
properties
• Periods: Horizontal
columns
Element Groups
• Groups 1A: Alkali Metals
• Group 2A: Alkali Earth
Metals
• Group 3A-4A: unnamed
• Group 5A: Pnictogens
• Group 6A: Chalcogens
• Group 7A: Halogens (salt)
• Group 8A: Noble Gases
Naming Ionic Compounds
-Ite
NO2-
-Ate
NO3-
Per…Ate Hypo-
Exceptions
ClO2-
ClO3-
ClO4-
OHCN-
SO3-
SO42-
-Ide
Monatomic
ClO-
•An ionic compound is a metal cation bonding to a non-metal anion
•Binary compounds are two nonmetal compounds, like NF3 (add prefix)
Protons, Neutrons, Electrons
and Isotopes
•
•
•
•
An Isotope is an atom with the same atomic
number but different mass numbers because of a
difference in the number of neutrons.
The atomic number of an element is the number
of protons
Neutrons and Protons add up to the mass
number of an ion/element
The number of electrons is determined by the
charge of the ion
Example
Element Atomic Mass # # of
Protons
#
# of
Neutrons
# of
Electrons
Na
11
23
11
12
11
Na+
11
23
11
12
10
Na
11
24
11
13
11
Percent Abundance
•
•
•
Percent Abundance is the percentage of
atoms of each isotope in a sample
% abundance=
(# of atoms of given isotope) x 100%
(total # of atoms of all
isotopes of that element)
Mass Mole Relationships/Percent
Composition
• Mass to Mole
Relationships:
Mass of A
Moles of A
Moles of B
•Percent Composition=
•(MA/MT) x 100%
Mass of B
Empirical and Molecular Formula
• Empirical Formula: (HINT-Assume 100g
sample)
= % composition ÷ (Smallest number of moles)
molar mass
• Molecular Formula:
(Mexp/Memp) x (Elements in Compound)
Example (Empirical Formula)
• You have a compound composed of 49.8% C, 5.15% H,
16.49% O, and 28.87% N. Find the empirical formula
• 49.48g C x 1 mol C = 4.120mol C = 4 mol C
12.011g C
1.031
• 5.15g H x 1 mol H = 5.110 mol H = 5 mol H
1.0079g H
1.031
• 16.49g O x 1 mol O = 1.031 mol O = 1 mol O
15.9994g O
1.031
• 28.87g N x 1 mol N = 2.061 mol N = 2 mol N
14.0067g N
1.031
C4H5ON2
Example (Molecular Formula)
• If the molar mass for the previous compound is 194.2
g/mol, what is its molecular formula?
• Theoretical molar mass =
4(12.011 g/mol C) + 5(1.0079 g/mol H) + (15.9994 g/mol O) + 2(14.0067 g/mol N)
= 97.0963 g/mol
• 194.2 g/mol ~ 2
96.0963 g/mol
• 2(C4H5ON2) =
C8H10O2N4
Balancing Reaction Equations/
Stoichiometry
• To balance a reaction
equation be sure to
have the same
number of elements
on the reactant and
products side.
• See mass to mole
relationship for
stoichiometry.
Limiting Reactants/ Percent Yield
• Using stoichiometry find which reactant
produces less of either product. This
reactant is the limiting reactant.
• (Mexp/Mtheor) x 100%
Hydrates
• Hydrates are compounds which
molecules of water are associated
with the ions of the compound.
• There is no simple way to predict
how much water will be present in
a hydrate compound; it must be
determined experimentally.
• Mass of Water=Mass of Hydrate
Compound – Mass of anhydrous
compound
Partial Pressure
• Partial pressure: PA=χAPTotal
Ptotal=((nA+nb+nc…)RT)/V
χA= na/ntotal
• Mole fraction: Ratio of the number of moles of
one substance to the total number of moles in a
mixture of substances
Ideal Gas Law
PV = nRT
P = Pressure (atm)
1atm = 760torr = 760mmHg
V = Volume (L)
N = # of moles
R = Rate
= .08206 (L∙atm/mol∙K)
T = Temperature (K)
K =°C + 273K
m/v = (PM)/(RT) = ρ
GAS….
Kinetic Molecular Theory
• Tiny particles surrounded
by much empty space
• Constantly moving
• Energy (speed2)
proportional to
temperature (T) in Kelvin
• Particles collide without
losing energy (preferably
an elastic collision)
R.M.S speed/Effusion/Diffusion
• √(3RT)/M = √u2
R= 8.314 J/mol∙K (J=kg∙m2/sec2)
T = Temperature (K)
M = Molar Mass (kg/mol)
• Effusion is going from a container into a
vacuum
• Diffusion is the mixing of two gases
• rate1/rate2= √M2/M1
Non-Ideal Gas Law (Van der
Waals)
•
•
•
•
•
•
(Preal+a(n/v)2)(Vreal-bn)=nRT
a= Attractive forces (atm∙L2/mol2)
b= Molecular volume (L/mol)
a(n/v)2 is the correction for intermolecular forces
bn is the correction for molecular volume
a and b are Van der Waals constants
GAS!