Gas Laws/State Of Matter CH 6 & 7 Flashcards
What are the laws that make up the Empirical gas laws
Boyle’s law, Charle’s Law, and Avogadro’s Law
What does Boyle’s Law state
When temperature is constant, Volume is inversely proportional to pressure
As pressure goes up, volume goes down
As pressure goes down, volume goes up
P1V1=P2V2
What does Charle’s Law state
When pressure and amount of gas are constant, volume is directly proportional to temperature
As temp goes up, volume goes up
As temp goes down, volume goes down
V1/T1 = V2/T2
*note: Not really true. Gas in a contained cylinder will have an increase in pressure as the temp goes up and VOLUME remains constant.
*Gay Lussc’s Law is a variation of Charles law which addresses this discrepancy (P1/T1=P2/T2)
What does Avogadro’s Law state
When temperature is constant, the volume of gas is directly proportional to the number of moles of gas
Volume goes up, #moles goes up
Volume goes down, #moles goes down
V1/n1=V2/n2
What does Gay-Lussac’s Law state
It is a variation of Charle’s law and states that when volume is constant, the pressure of a gas is directly proportional to the absolute temperature
Temp goes up, pressure goes up
Temp goes down, pressure goes down
P1/T1 = P2/T2
What is the combined gas laws?
It combines Boyles, Charles, and Avogadro’s Law
P1V1/n1T1 = P2V2/n2T2
What is the Ideal Gas Law
It describes the behavior of an ideal gas under all conditions, but it does not account for real gases that we deal with in real life.
PV=nRT
R is constant
n = # moles
P = pressure
V = volume
T = temp in kelvin
What is the universal gas constant?
R is the universal gas constant
R = PV/nT
R = 0.08206 Latm/molK
What does R equal
R = 0.08206 Latm/molK
What is STP
The Standard Temperature and Pressure
It is a commonly cited set of conditions that helps determine R when conditions are specified
STP is defined to be exactly zero degrees C or 273.15K with a standard pressure 1 Bar
1Bar = 100kPa = 1atm = 760 torr = 101325 Pa or 101.325 kPa
What is the standard molar volume of a gas
The volume that exactly 1 mole of ideal gas occupies under STP conditions
1 mol = 22.71 L
What do we need to know in order to calculate gas density
mass and volume
Density = m/V
How do we calculate density if we have known temperature and pressure
use the ideal gas law (n=PV/RT) to get moles of each component
then obtain the molecular mass of each component
Multiply n by the molecular mass of each component to get the fraction of mass
Substitute those fractions into the Density = m/v
Volume should be given and remember gas is non-reactive and their volumes are additive (so if N2=0.79L and O2=0.21L the the V=0.79+0.21=1.0L)
What does Dalton’s law state
the total pressure of a gas mixture is equal to the sum of partial pressures of each component of gas
Ptotal = P1 + P2…..+Pn
To calculate partial pressure,
Pi = Xi * Ptotal
where Xi is the mole fraction in a mixture
And Ptotal = nRT/V
What is relative humidity
the measure of the saturation of water in the air
One way to calculate relative humidity is to divide the amount of water in the air by the solubility of water in the air
Relative humidity is a function of temperature
as temp goes up solubility of water in air goes up
What is the solubility of water in the air
It is the maximum amount of water that a given volume of air can accommodate
How much N2 and O2 are in the air?
79%N2 and 21% O2
We usually measure water vapor pressure in air as
47mmHg
What is the dew point temperature
it is the condensation formed when a sample is cooled to a temperature where the actual concentration of water exceeds the solubility of water in air
How can we calculate of relative humidity using vapor pressure and partial pressures
RH = partial pressure of water/vapor pressure of water all times 100%
what is the Kinetic Molecular Theory of Gases
It describes ideal gases based on 4 tenents
what are the 4 tenants of the kinetic molecular theory of gases
1) Gases consist of small particles while volume is negligible compare to the volume of gas
- not really true: real gas at high pressures crows more gas molecules into same volume
2) Gas molecules are in constant, random motion
3) The molecules in the sample show a range of kinetic energies, but the average KE depends only on the temperature
4) There are no attractive or repulsive forces between the gas particles, so all Collins are elastic
- not really true: real gases do have an attractive force as seen in liquid state & low temperatures
The average KE is dependent on what
Temperature
KE = 3/2kT
k= Boltzmann’s constant
Boltzmann’s constant (k) equals
1.38 x10^-23 J/K
1 mi = meters (m)?
1,609m
1hr = sec?
3600s
What is the difference between Diffusion and Effusion
Diffusion is the movement of a substance from an area of high to low concentration
Effusion is the movement of gas through a small opening
What does Graham’s Law state
The rate of effusion is inversely proportional to the square root of the molecular mass (M)
What does the Vander de Waals Equation do
It corrects for the intermolecular attractions between gaseous molecules and for the finite volume of the gas molecules
What does The Molecular Theory of Matter describe
it describes all states of matter and the conversion between the states by considering the structures of molecules comprising matter and how those molecules interact
What are the 3 commonly encountered states and what characterizes them?
Solid: characterized by shape and volume
Liquid: characterized by a definite volume, but NOT shape. It conforms to the shape of the canister.
Gas: Have neither Definite shape or volume. Gas will expand to fill available space.
Do gases have intermolecular forces?
No
the move freely and collide freely
Which states are compressible
Liquids and Solids
Which states are considered fluids
Gases and Liquids
Melting is
the conversion of a solid into a liquid
Freezing is
the conversion of a liquid into a solid
Vaporization is
when a liquid vaporizes into a gas
Condensation is
when a gas condenses into a liquid
Deposition is
when a gas converts into a solid
Sublimation is
when a solid converts into a gas without having to become a liquid first
What are intermolecular forces
Forces the determine how molecules interact with one another. They arise because of the attraction of opposite charges and produce an inherent repulsion.
Determined by chemical bonds that hold atoms together
They are electrostatic in nature
4 types of IMF: dipole-dipole, hydrogen bonding, London forces, and ion-dipole interactions
What are Dipole-Dipole interactions
Dipole attractions between the opposite (partial) charges of POLAR molecules
What are Hydrogen Bonding interactions
Special type of dipolar interaction only possible when a hydrogen atom is directly bonded to F, O or N.
Stronger than Dipole-Dipole interactions
It is the most important intermolecular force
What are London forces
It is the result of an instantaneous dipole that is created whenever electrons in a molecule are unevenly distributed.
All molecules and atoms that have electrons, exhibit London forces.
Larger molecules show more London forces because larger molecule have more electrons
What are Ion-Dipole attractions
Attraction between an ION and POLAR molecule
This attractions allows ionic solids to dissolve in water
What are valence electrons
electrons in partially filled shells.
electrons in the highest energy or valence (shell).
8 total valence electrons for a stable element
Noble gases
have 8 valence electrons in outer shell. Most stable
What are isoelectric species
elements that are only one or two atomic numbers away from a noble gas form
What are core (kernel) electrons
electrons in filled shells.
virtually inert because they represent complete collections of electrons, very energetically expensive to break up a complete set
Which bonds are stronger, covalent or ionic
Ionic and for this reason every ionic compound is solid at room temperature and pressure.
What is the valence bond theory
theory that explains how covalent bond form through the sharing of valence electrons and the electron structure of those molecules
What amount of energy makes you stable
less energy
What are isomers
compounds that different but have the same molecular formula
What is the VSEPR theory
Valence Shell Electron Pair Repulsion explains that atoms are bound into molecules by shared pairs of electrons.
Electrons dislike each other because like charges repel each other
Whether they are lone pairs of electrons or bonding pairs of electrons, the pairs try to get as far apart in space as geometrically possible
What angle does a linear molecule form
Angle between bonds is 180 degrees
What angle does trigonal planar molecule form
Angle between bonds is 120 degrees
What angle does a tetrahedral molecule form
Angle between bonds is just over 109 degrees
What angle does a bent molecule form
Angle varies, but mainly know it is non linear
What angle does a pyramidal molecule form
It is like trigonal (120 degrees) the only difference is it has a point the forms that “pyramid” shape
What element is the most electronegative
Fluorine
Describe a non polar bond
two atoms of IDENTICAL electronegativity bonded together
Describe a polar bond
two atoms of DIFFERENT electronegativity bonded together
What are some non polar elements we will work with
Nitrogen, Oxygen, Carbon Dioxide
Substances that have greater intermolecular attractions will have what kinds of surface tension
Greater surface tensions
What is surface tension
the force acting on the surface of a liquid cause by the attraction of molecules in the surface later; makes liquid surface act as it were elastic-like
What is the IM force of water
hydrogen bonding
Does water have high or low surface tension
High
What is capillary rise (capillary action)
it is a second effect caused by surface tension. It is the tendency of fluid ratio to rise into a narrow-diameter tube.
the rise will depend of the diameter of the narrowest tube.
What is Laplace’s Theory
Theory used to calculate the distance a fluid will rise in a capillary.
When a liquid is in contact with another surface, it has a curling the creates a pressure difference, this theory has formulas to calculate that
What is the surface tension of water
0.072 N/m
The radius (R) in the Laplace formula represents
(R) is a function of the contact angle and the radius of the tube, r. Since r and R form two side of a right triangle, R is give by
R = radius (r)/ cosign of angle
What do we use to calculate upward pressure of a liquid
Laplace forumla
What do we use to calculate downward pressure of a liquid
P=pgh
p=density
g=gravity
h=height
Surface tension is proportional to
the radius
What is a physical advantage of having an aneurysm?
Lowers surface tension on a blood vessel
What is a surfactant
A soap or detergent used to reduce the surface tension of a solvent
Surfactant molecules will strike to get the greasy non polar hydrocarbon tails away from the polar water molecules via 3 strategies, what are they
Formation of:
monolayers
bilayers
micelles
Soaps are derived from
fats or oils (triglycerides) through chemical process called saponification
Detergents are synthesized from
soaps
The molecular structure of detergents can be tweaked to optimize the physical properties of the detergent
Detergents can be cationic, anionic, or nonionic
What is the structural feature of soaps and detergents
both have a polar (hydrophilic) HEAD and a non polar (hydrophobic, greasy) TAIL
Describe monolayer surfactants
In forming a monolayer, surfactant molecules stick their polar heads onto the water, while their greasy tails stick out of the surface of the water
increasing surfactant will decrease surface tension of water
What is an example of how we use monolayer surfactants to reduce surface tension
We give premature babies monolayer surfactants to decrease the surface tension of the lungs
By adding this type of detergent, the water in the lungs becomes less cohesive and the surfaces in the lungs are less likely to stick together
Describe bilayer surfactants
The tail of the surfactant molecules can dissolve in each other to form a double layer (bilayer)
What is an example of a bilayer surfactant we use
For bactericidal properties
Describe micelles surfactants
the greasy tails can dissolve in each other forming a spherical structure
What happens with increased viscosity
it increases with increasing molecular forces
it increases the resistance to flow
What is viscosity
a measure of a fluid’s resistance to flow
What is the relationship of vapor pressure and temperature
directly proportional as temperature rises, vapor pressure will rise and so will the volatility of a liquid
What is the relationship of vapor pressure and IM forces
Substances that have greater IM forces will have lower vapor pressure
What is volatility
it is an non-quantitative term used to describe the tendency of a liquid to evaporate
What is the Clausis-Clapeyron Equation
Formula that relates the vapor pressure of a liquid (P) to the kelvin temperature (T)
where A & B depend on the liquid
To free log (P) use the antilog (P)
What does the vapor pressure of a volatile liquid determine
the maximum mole fraction of that substance in a gas phase in contact with that volatile liquid
With a gas, the mole fraction equals
mole fraction = volume fraction = pressure fraction
What is the relationship between boiling point and IM forces
with increasing IM forces, the boiling point will increase
what is boiling point
boiling point of a liquid substance is the temperature at which the vapor pressure of a liquid is equal to 1 atm pressure
What does boiling point correspond to
The average KE sufficient enough o overcome the IM forces that hold a molecule in the liquid state
What is the relationship between boiling point and pressure
because gases respond strongly to pressure, the boiling point of a liquid is highly dependent on pressure
As the boiling point increases, the pressure will increase
What is the normal boiling point of water
100 degrees C or 373K at 101kPa
Calusius-Clapeyron Equation can be used to quantify the relationship between boiling point and temperature, what is the formula for that
What is the relationship between melting point and IM forces
as IM forces increase the melting temperature increases too
What is melting point
temperature at which the solid state reversibly passes into the liquid state, also known as the freezing point
The melting point corresponds to
the average KE sufficient to overcome the IM forces that hold the molecules in the solid state
What is molar enthalpy of fusion (Hfus)
the heat necessary to convert 1 mole of a SOLID into a LIQUID at its normal MELTING point
What is molar enthalpy of vaporization (Hvap)
the heat required to convert 1 mole of a LIQUID into a GAS at its normal BOILING point
What is the relationship between Hfus and Hvap
they both are endothermic and represent a amount of energy that must be added to a sample in oder for the phase transition to occur
Hvap > Hfus and this is true fore all substances
Heat of fusion represents
the amount of energy necessary to overcome the IM forces to the point that the molecules can start to move around each other
Heat of vaporization represents
the amount of energy necessary to overcome all the IM forces that the molecule can escape into the gas phase
Triple point on the phase diagram represents
the single temperature and pressure combination where all three phases can exist in equilibrium with each other
the solid-liquid equilibrium line defines
the melting point of the solid into the liquid state
the liquid-gas equilibrium line defines
the boiling point of the liquid at various pressures. it terminates at a point known as the critical piont
The solid-gas equilibrium line defines
sublimation of solid into gas state without become a liquid first
supercritical fluids
have the flow properties of gases but densities similar to liquids and have no surface tension. make for terrific solvents
Ex; carbon dioxide, excellent solvent for extracting caffeine from coffee
