Chemistry Exam 3 Key Topics
Boyles Law
volume of a gas varies inversely with pressure (fixed amount of gas at constant T) P1V1=P2V2
Avogadro's Law
volume of a gas varies with the number of moles (constant T and P) V1/n1=V2/n2
Molar volume
volume of exactly 1 mol if gas under STP conditions
bond angle
angle formed between three atoms
Electron pair geometry
arrangement of the electron pairs about the central atom in a molecule
quantum mechanical model of the atom
atomic concept that recognizes four quantum numbers by which electron energy levels may be described - you can not know precisely where the electron is and study as a wave -Louis de Broglie - formed the wave model (treated e- as waves) Erwin Schrodinger - detailed mathematics (principle quantum # = principle energy level)
octet rule
atoms tend to gain, lose, or share electrons in order to achieve a noble gas configuration (8 valence electrons)
metallic bond
attractive forces between negatively charged electrons and posititvely charged metal atom nuclei
resonance hybrid
average of resonance structures that represents the actual molecule.
pressure
force per unit. P=Force/Area
Chemical bond
forces that hold atoms togehter to form molecules or polyatomic ions, that hold atoms together in metals, or that hold oppositely chcarged ions together to form ionic compounds
tetrahedral molecular geometry
four electron pairs, four bonded atoms, 109.5 degrees
trigonal pyramidal molecular geometry
four electron pairs, three bonded atoms, 109.5 degrees
bent molecular geometry (2 bonds)
four electron pairs, two bonded atoms, 109.5 degrees
Is the pressure exerted by a gas uniform in all directions?
gas is uniform in all directions by exerting pressure the same in all directions. liquids are not uniform because the pressure is greater at the bottom due to gravity
Law of Combining Volumes
gases react in volumes in the ratio of small whole numbers
alkali metals
group 1A, ns1 valence electrons
alkaline earth metals
group 2A, ns2 valence electrons
noble gases
group 8A, ns2np6 Very stable due to a filled valence (octect)
Paul exclusion principle
only two electrons can occupy an orbital and they must have opposite spins'
Amonton's Law
pressure of a gas varies directly with temperature (fixed amount of gas at constant volume) P1/T1 = P2/T2
covalent bond
sharing of one or more pairs of electrons
single bond
sharing of one pair of electrons
triple bond
sharing of three pairs of electrons
double bond
sharing of two pairs of electrons
alloy
solid mixture of two or more elements that has the properties of a metal
STP (standard temperature and pressure)
standard temp standard pressure
ionic bonds
strong electrostatic forcecs that hold the ions in fixed positions within the crystal lattice. 1. the lines between the ions in the ball-and-stick model are simply reference lines to show the relative positions of Na+ and Cl- 2. a space filling model more correctly shows how the ions are packed together. 3. six sodium ions surround each chloride ion an vice versa.
Each Principal Energy Level has a ____.
sub-level (# of sub-levels is the same as the principal energy level) S, P, D, and F sub level
electronegativity
the ability of an atom of an element in a molecule to attract bonding electrons to itself
electron pair angle
the angle formed by two electron pairs and the central atom
A 10.0L balloon filled with helium gas at 655 mmHg is compressed to 8.6L. What is the new pressure of helium gas inside the balloon
P1V1=P2V2 P2=P1V1/V2 P2=10.0L*655 mmHg/8.6L P2=761.63 mmHg
Halide ion
(Gained e-) are isoelectric (same # of electrons w/ noble gases that follow them in z)
The Kinetic and Molecular Theory of Gases
1. A gas consists of particles and empty space 2. The volume occupied by the gas particles is negligible compared to the total volume of the space available. 3. The attractive forces between the gas particles are also negligible 4. The average kinetic energy of the gas particles is proportional to the temperature (in K) 5. Gas perticles collide with oter gas particles and with the walls of the container without a change in total kinetic energy (at constant T)
Classify each of the following quantities as continuous or quantized
-something continuous may have any value - something quantized has only certain possible values -milk from a store - quantized -amount that you weigh - continuous -paper money in the US - quantized
Standard temp
0 degrees C
Gas Pressure per units
1 atm = 760 mmHg 1 atm = 760 torr 1 atm = 101,325 Pa 1 bar = 100 kPa = 100,000 Pa in the us 760 mmHg = 29.92 Hg 1 atm = 14.70 Lbs/in^2 (psi)
Standard Pressure
1 bar
How many sub levels are there with n=1 in an atom?
1 sub level
Size of atom
1. Going across a period: size decreases with an increase in nuclear charge (z). (A stronger positive charge can bring the e- closer to the nucleus) 2. Going down a group the size increases with n -(principle quantum number) (the orbitals are further from the nucleus) ns
drawing lewis structure
1. calculate the total number of valence electrons. For ions, add or subtract electrons accordingly 2. determine the central atom (usually its the least electronegative atom, H is an expection) 3. Show which atoms are attached to which by connecting them with a single bond 4. complete the octets around all of the atoms bonded to the central atom. Exception: H! 5. place any leftover electrons on the central atom.
vacuum pressure
1.3X10^-1 torr
What is the maximum number of electrons possible with n=1 in an atom?
2 e-
λ*v=constant
2.99X10^8 1 nm= 10^-9 707x10^-9 x 4.23x10^4 = 2.99x10^8
Consider the following reaction. S(s) + O2(g) -> SO2(g) How many liters of O2 are needed to form 35.2 L of SO2, both gases being measured at 741 Torr and 26 degrees C?
35.2 L SO2 * 1 L O2/ 1 L SO2 = 35.2 L O2
Automobile air bags are inflated by nitrogen gas generated by the rapid decomposition of sodium azide, NaN3: 2 NaN3 (s) -> 2 Na(s) + 3 N2 (g) If an air bag has a volume of 36 L and is to be filled with nitrogen gas at STP, how many grams of NaN3 must be decomposed?
36 L N2 * 1 mol N2/22.7 L N2 = 1.58590384 mol N2 1.585903084 mol N2 * 2 mol NaN3/ 3 mol NaN3 * 65.02 g NaN3/ 1 mol NaN3 = 68.74361234 g or 69 g NaN3
How many 4d orbitals are there in an atom?
5 orbitals What is the maximum number of electrons possible in a set of 4d orbitals? - 10 e- max
"space" (LEO)
7.5X10-8 torr
A 8.6 L balloon filled with helium gas at 75 degree C is taken outside, where the temperature is 14 degree C. Does the balloon shrink or expand?
8.6L/348K = v2/287K v2=v1t2/t1 v2=8.6*287/348 v2=7.1L shrinks
Quantum Mechanics
Branch of science that describes the quantum behavior of photons and subatomic particles
Wavelength (λ)
Distance between peaks and waves
Boher Model of the atom
Electron energies and orbit radii are quantized, or limited to specific values of n. -can not have an in between energy level -n=1 is the lowest energy level -works only for the hydrogen atom.
According to the Boher Model how do electrons move?
Electrons can move between allowed energy levels. Relaxation from an excited state to the ground state releases levels in the form of a visible light (UV light), explaining line spectra. -Electrons are orbiting the nucleus at certain Radii and energy levels -Limitation is that it only works with the hydrogen atom.
valence electrons
Electrons on the outermost energy level of an atom
Electromagnetic radiation
Energy in a form of electric and magnetic waves including gamma rays, x-rays, UV rays, visible & infrared light, microwaves, radio waves
First/second/third ionization energy
Energy required to remove the first/second/third electron from a neutral gaseous atom of an element.
Max Planck
German physicist who developed quantum theory and was awarded the Nobel Prize for physics in 1918. - Electromagnetic energy could be absorbed or emitted by atoms only in quantitized form. - E = h*frequency
Halogens
Group 7A ns2np5
Hydrogen
H group 1A, 1S1 valence electron Can act as a metal or a non metal Metal H+ nonmetal H-
metalloids (semimetals)
Have properties between those of metals and nonmetals (can act as metal or nonmetals)
Einstein Photoelectric Effect
He found that you can eject an electron from a metal surface by shining light above a certain frequency.
A 34 L tire has a pressure of 28 psi at 75 degrees C. What is the pressure at 14 degrees C?
P1/T1 = P2/V2 P2 = P1T2/T1 P2 = 28 psi * 287 K/348K P2 = 23 psi
Combined Gas Law
P1V1/T1 = P2V2/T2
In the Bohr model of the hydrogen atom, the e- occupies distinct energy states. One transition between energy states of the hydrogen atom is represented by the pic. N=4______ N=3______ N=2______ N=1 ^
In this transition an electron moves from n=1 to n=2 level, energy is absorbed in this process, the electron moves further from the nucleus How many sublevels are there with n=1 in an atom? - 1 sub level
Principle of the quantum number (n):
Integer value representing allowed energy states for an electron is an atom
A 25.0 mL bubble is released from a diver's air tank at a pressure of 4.00 atm and a temperature of 11 degrees C. What is the volume (mL) of the bubble when it reaches the ocean surface, where the pressure is 1.00 atm and the temperature is 18 degrees C?
P1V1/T1 = P2V2/T2 V2=P1V1T2/T1P2 V2 = 4.00atm * 25.0 mL * 291K/284K * 1.00 atm V2 = 102 mL (increased)
principle quantum number = principle energy level
N = 1,2,3,4,5,6,7,8,9,10.....
Consider the following reaction. S(s) + O2(g) -> SO2(g) How many liters of O2 are needed to form 35.2 L of SO2, both gases being measured at 741 Torr and 26 degrees C but the O2 is at 847 Torr and 17 degrees C?
SO2 = PV = nRT n=PV/RT = 741 torr * 35.2 L/62.4 (L*Torr/Mol*K) * 299K = nSO2 = 1.39799311 mol nO2 = 1.397993311 mol SO2 * 1 mol O2/1 mol SO2 = 1.39799311 mol V = n RT/P = 1.39799311 mol * 62.4 (L*Torr/mol*K) * 290K/847 Torr = 29.86787124 or 29.9 L
Lewis symbol (electron-dot symbol)
The chemical symbol for an element, with a dot for each valence electron.
Frequency (v)
The number of wavelengths that pass a fixed point per second.
Electromagnetic spectrum
The range of frequencies and corresponding wavelengths of electromagnetic radiation.
Solid Na generated within an automobile airbag undergoes a secondary reaction that generates even more N2 (g): 10 Na(s) + 2 KNO3 (s) -> K2O + 5 Na2O(s) + N2(g) If an airbag inflates to a pressure of 1.15 atm abd 26.0 degrees C and generates 25.8 g of Na, what is the volume of the additional N2 that is generated by the secondary reaction under these conditions?
V = 25.8 g Na P = 1.15 atm T = 299 K PV=nRT 25.8g Na * 1 mol Na/22.99 g Na * 1 mol N/10 mol Na = 0.11222271 mol V = nRT/P = 0.11222271 mol * 0.0824 (l*atm/mol*k) * 299K/1.15 atm = 2.39 L
What happens to he density of a gas when it is compressed? When it is allowed to expand?
When you compress the density increases when you expand the density decreases.
line spectrum
a spectrum showing only certain discrete wavelengths - provides important info on electrons.
ionic compound
compound made up of ions
molecular compound
compounds made up of molecules, composed of nonmetals.
isomers
compounds with the same molecular formula but different geometric structures
continuous spectrum
continuous band of wavelengths
wedge-and-dash diagrams
dash - these bonds are behind the page straight line - these bonds are in the plane of the page wedge - these bonds extend in front of the page.
Crystal Lattice
definite geometric structure of ionic solid
valence shell electron repulsion (VSEPR)
electron groups are arranged as gar apart as possible to minimize repulsion. -determines the shape
nonpolar covalent bond
equal sharing of one or more pairs of elelctrons.
metallic character
exhibition of physical and chemical properties of metals
what is the density of a gas compared to a liquid and a solid?
find the density of gases weigh less than liquids and liquids less than solids.
electron configuration
the arrangement of electrons in the orbitals of an atom -ground state distribution of e- among orbitals -1. The ground state, e-fill the lowest energy level -2. No orbital can contain more than two e-.
manometer
laboratory device for measuring gas pressure total pressure at the same level in the right leg is the pressure of the atmosphere, Pa, plus the pressure difference, Phg; thus Pg=Pa+Phg The total pressure in the closed leg is Pg+Phg, which is equal to the atmospheric pressure, Pa. Equating and solving for Pg yield Pg = Pa - Phg
Barometer
laboratory devices for measuring atmospheric pressure
generated by the rapid decomposition of sodium azide, NaN3: 2 NaN3 (s) -> 2 Na(s) + 3 N2 (g) If an air bag has a volume of 36 L and is to be filled with nitrogen gas at 1.5 atm and 26 degrees C, how many grams of NaN3 must be decomposed
molar volume V/N = RT/P = 0.0821 L*atm/mol*k * 299.0K/ 1.15 atm = 21.346 L 36 L * 1 mol N2/21.346 L * 2 mol NaN3/3 mol N2 = 65.02g NaN3/1 mol NaN3 = 73.10409449 g NaN3 or 73 g NaN3
polar molecule
molecule in which an asymmetric charge distribution results in positive and negative poles
wave-particle duality
the concept that all matter and energy exhibit both wave-like and particle-like properties
first ionization energy
the energy required to remove the first electron from an atom IE1 <IE2 < IE3
molecular geometry
the shape of a molecule
Charles Law
volume of a gas varies directly with temperature (fixed amount of gas and constant pressure) (kelvin) V1/T1 = V2/T2
trigonal planar molecular geometry
three electron pairs, three bonded atoms, 120 degrees
bent molecular geometry
three electrons, two bonded atoms, 120 degrees
linear molecule geometry
two electron pairs, two bonded atoms, 180 degrees
resonance structures
two or more equivalent Lewis Structures involving alternate electron placement
polar covalent bond
unequal sharing of one or more pairs of electrons
