Ch 5 and 11
A partial pressure is the pressure exerted by just one type of gas in a mixture. A partial pressure is calculated using only the number of moles of that particular gas, instead of the total number of moles: P1=n1RT/V, P2=n2RT/V, P3=n3RT/V, etc. The sum of the partial pressures is equal to the total pressure in the mixture: Ptotal=P1+P2+P3+⋯
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According to the ideal gas law, the changes in pressure and temperature will cause a change in volume. Volume and pressure are inversely related, while volume and temperature are directly related.
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In a simple-cubic (sc) crystal lattice, the unit cell is composed of eight atoms that each take a corner of a cube. (Figure 1) Because this is such an inefficient way to pack atoms, it is a rare arrangement for metals. Only one metal is known to pack in this form: polonium, Po.
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PV=nRT which can be rearranged as n=PV/RT Given the number of moles of a gas and its molar mass, you can calculate the mass of the gas. Since density is equal to the ratio of the mass and volume, you can then divide by the volume to find density.
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The partial pressure and the average kinetic energy of a gas are not related to the mass of the gas particles. The rate of effusion and the average velocity of gas particles decrease as the mass of the particles increases.
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To calculate the heat that is evolved in converting 1.00 mol of steam at 135.0∘C to ice at -45.0∘C use the three following equations to solve for ΔQ and ΔH values: q = mCs(Tf−Ti) q = n × ΔH1 mol ΔQtotal=ΔQvapor+ΔHvaporization+ΔQliquid+ΔHfusion+ΔQsolid
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Dipole-dipole forces result from
... the attraction of the positive end of one polar molecule to the negative end of another polar molecule. Compounds consisting of atoms with different electronegativities may have a dipole moment, or partial charge, caused by an asymmetry of electrons.
A dipole moment tends to stabilize the liquid state of the compound as molecules align to form attractive molecular interactions. A liquid state that is more stable, that is one that is held together by stronger dipole forces, will have a high boiling point since it takes
...more energy to break these intermolecular forces.
if a substance has low intermolecular forces....
..it evaporates very easily (volatile) (e.g gasoline, perfume) ..has high vapor pressure
if a substance has high intermolecular forces....
..it has high surface tension, MP, BP, and ..low vapor pressure
When atm is used for pressure and L for volume, the appropriate R value is
0.0821 L⋅atm/mol⋅K.
at STP, 1 mole of an "ideal gas" occupies,
22.4 L
The melting point of a solid is related to the way in which that substance is held together. High melting point ⇓ Low melting point .
Covalent-network solids (High) Metals and ionic solids Molecular solids (Low)
only atoms that can form hydrogen bonds
O and H with (O-H-F,O,N) ... F,O, or N
When n and V are fixed, the equation can be rearranged to take the following form where k is a constant: When n and P are fixed, the expression becomes
P/T=nR/V=k or (PT)initial=(PT)final V/T=nR/P=k or (VT)initial=(VT)final
when using ideal gas law When n and V are fixed, the equation can be rearranged to take the following form where k is a constant:
PT=nRV=k or (P/T)initial=(P/T)final
Ideal Gas Law
(PV=nRT) describes the relationship among pressure P, volume V, temperature T, and molar amount n.
pressure exerted by a given number of ideal gas particles is the same whether the sample consists of all one type of particle or a mixture of different kinds of particles. Therefore, the pressure exerted by a mixture of gases can be expressed as follows:
Ptotal=(n1+n2+n3+⋯)RT/V=n-total(RT/V)
According to Boyle's law, for a fixed quantity of gas at a given temperature, what quantity relating pressure P and volume V is constant?
P×V
what is R?
R is a proportionality constant. The units of R are determined by the units of pressure and volume used in the equation. When atm is used for pressure and L for volume, the appropriate R value is 0.0821 L⋅atm/mol⋅K.
statement about a sample of gas containing molecules of different masses that is true?
The average kinetic energy depends only on the temperature. However, a heavier molecule will move more slowly than a lighter molecule if both have the same kinetic energy.
gas molecule true facts
The average speed of gas molecules increases with increasing temperature. There are gas molecules that move slower than the average. The average kinetic energy of gas molecules decreases with decreasing temperature. The temperature of a gas sample is related to the average kinetic energy.
partial pressure is the pressure exerted by just one type of gas in a mixture. A partial pressure is calculated using only the number of moles of that particular gas, instead of the total number of moles
The sum of the partial pressures is equal to the total pressure in the mixture:
when using ideal gas law When n and P are fixed, the expression becomes
VT=nRP=k or (V/T)initial=(V/T)final
Charles's Law
a container of gas held at constant pressure, the volume and temperature are directly proportional. (v/t)
phase diagram
a graph that shows what state of matter is present at different temperatures and pressures.
polar molecule
a molecule that does not have symmetry
nonpolar molecule
a symetrical molecule, no matter the type of bonds that make it up
relationship between the volume and temperature of a gas. For a container of gas held at constant pressure, the volume and temperature
are directly proportional.
relationship between the pressure and volume of a gas. For gas at a constant temperature, pressure and volume
are inversely proportional.
critical point
at pressure above the critical point pressure the liquid to gas states are no different.
intermolecular forces
attraction of the (+) end of one molecule to the (-) end of another. responsible for solubility.
dipole-dipole attractive force
between polar molecules
at lower atmospheric pressure there is less of a force to overcome, the boiling point
decreases
Hydrogen bonding is a particularly strong type of
dipole-dipole force that occurs when hydrogen is attached to nitrogen, oxygen, or fluorine. Water is an example of a substance in which hydrogen bonding occurs. Because of oxygen's high electronegativity and the electron deficiency of the hydrogen atom, the hydrogen atoms are attracted to the lone pairs of electrons on the oxygen of another water molecule.
Hydrogen bonding is a subset of
dipole-dipole forces.
temp and vapor pressure relationship
directly related
the lighter the molecules of the gas, the more rapidly it effuses. Mathematically, this can be expressed as
effusion rate∝1/√m The lighter the molecules of a gas, the greater the rms speed of the molecules, and the more rapidly the gas effuses.
intermolecular bonds
form between molecules x-H-x
effusion is the
gradual escape of gas molecules through microscopic holes in their container.
diffusion is the
gradual mixing of two substances owing to the movement of their particles.
miscibility
how well two different materials mix together (mixability). like disolves like polar-polar, non-non
at higher atmospheric pressure there is more of a force to overcome, the boiling point
increases
The average speed of gas molecules increases with
increasing temperature. There are gas molecules that move slower than the average. The average kinetic energy of gas molecules decreases with decreasing temperature. The temperature of a gas sample is related to the average kinetic energy.
water readily breaks down
ionic compounds due to the negative charge on them and it being polar
The vapor pressure of a liquid is the pressure exerted by its vapor when the liquid and vapor states are in equilibrium. The relationship between vapor pressure P and temperature T is expressed by the Clausius-Clapeyron equation
lnP2/P1=ΔHvap/R(1/T1−1/T2) where P1 and P2 are the vapor pressures at the absolute temperatures T1 and T2, respectively, ΔHvap is the heat of vaporization of the substance in joules per mole, and R is the ideal gas constant, which is equal to 8.3145 J/(mol⋅K). The heat of vaporization of water is 4.07×104 J/mol.
The rate of effusion and the average velocity of gas particles decrease as the
mass of the particles increases.
dipole
patial charge on bonded atoms indicating which is more positive or negative
The relative rate of effusion can be expressed in terms of molecular masses m1 and m2 as
rate of gas 1 effusion/rate of gas 2 effusion=√m2/m1
Viscosity is
resistance of a liquid to flow.
covalent bond
sharing e-
Which factors affect the vapor pressure of a liquid?
temperature type of liquid amount of solute
The normal boiling point of a liquid is the
temperature at which its vapor pressure equals 1 atm. This is the point where there is a transfer from liquid to gas phase.
london force
the attractive force between non-polar molecules. strength varies with size of molecule
Surface tension is
the energy required to increase the surface area of a liquid by a certain amount.
The partial pressure and the average kinetic energy of a gas are not related to
the mass of the gas particles.
partial pressure
the pressure that any unique gas adds to the total pressure of a system. Ptotal=PA+PB+... The partial pressure of an individual gas can be used in stoichiometric calculations involving chemical reactions.
effusion
the process in which a gs flows through a small hole in a container
The speed of a particle with average kinetic energy is called
the root mean square (rms) speed, vrms.
tripple point
the temperature and pressure in which all three states of matter can exist in equilibrium
The stronger the forces of attraction, the more difficult it is for the molecules to move past one another, thus increasing
the viscosity and surface tension of the liquid.
molar volume
the volume of one mole of substance.
H and C can't form hydrogen bonds becasue
they share electrons evenly
polar bond
two atoms in which electrons are shared unequally. Because of this, one end of the bond has a fractional negative charge and the other a positive charge.
Avogadro's Law states that at a given temperature and pressure, what quantity is constant?
v/n
All substances have dispersion forces, also known as London forces. These forces are
very weak and are only important in the absence of any other intermolecular force. Nonpolar covalent molecules and single-atom molecules are examples of substances that lack all other intermolecular forces except for dispersion. Dispersion forces result from shifting electron clouds, which can cause a weak temporary dipole.
The kinetic energy of a molecule determines its speed. It is important to realize that not all molecules in a sample will have the same kinetic energy, which is why we refer to the average kinetic energy and the average speed. The speed of a particle with average kinetic energy is called the root mean square (rms) speed, vrms. The rms speed may be expressed by the following equation:
vrms = √3RT/M where R is the ideal gas constant, T is the absolute temperature, and M is the molar mass of the substance in kilograms per mole. The constant motion of gas molecules causes diffusion and effusion.
nonpolar bond
when the difference in electronegativity between the two atoms is less than 0.4.
To calculate the rms speed and relative rates of effusion of gas molecules. In a given sample of gas, the particles move at varying speeds. The root mean square speed (rms speed) of particles in a gas sample, u, is given by the formula
√u=√3RT/M where T is the Kelvin temperature, M is the molar mass in kg/mol, and R=8.314J/(mol⋅K) is the gas constant.
