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Standard Molar VolumeTo compare one gas to another, it is convenient to define a set of conditions:Standard Temperature and Pressure

At STP, one mole of any gas has a volume of:22.4 L =

(This is a cube about 28cm or 11 in on each side.)Problem: a) How many moles of methane gas, CH4, are in a1.00 x 105 L storage tank at STP?

b) How many grams of methane is this?

c) How many grams of CO2 could the same tank hold?

8.8 The Combined Gas LawThe previous relationships can all be combined into a single equation.

This relationship is true under any set of conditions.

This is typically used when you are changing conditions for a given sampleof a gas.This formula can be used to solve any of the previous gas laws. If a variableis constant, simply eliminate it!

T must be in KV & P can be inany units.

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Problem: A sample of CO2 gas in flask A (V= 265 mL & P= 136.5 mm Hg,at T= 22.5 °C).The sample is moved to another flask (B), with (P= 94.3 mm Hg &T=24.5 °C). What is the volume of flask B?

8.10 The Ideal Gas LawDerivation:

P1V1 = P2V2= a constant at all sets of conditionsn1T1 n2T2

Since the relationship is always true, it is always equal to a constant, R.

R =

Whenever we use R,

The relationships among the four variables P, V, T, and n can be rearrangedinto a single expression.

Ideal Gas Law

V must be inP must be inT must be in

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Problem: A sample of H2 gas has a volume of 5.86 L at 0 °C. It exerts apressure of 1140 torr. How many moles of H2 are in this sample?

8.11 Dalton’s Law of Partial PressuresStates that:

The pressure of a mixture of gases= the sum of the pressure exerted by each individual component= the sum of the partial pressures.

The pressure contributed by each gas is independent of any other gas present.Each gas contributes to the pressure as if it was the only gas present in the entirevolume.

Air is a mixture of about 21% oxygen, 78% nitrogen, and 1% argon.This means that 21% of atmospheric pressure is caused by the oxygen, 78%by nitrogen, and 1% by argon.Pi = (Ptotal) (% i) Note: % I must be expressed as a decimal.)If the total air pressure is 780 mm Hg, the partial pressures of each gas are:

oxygen 780 mm Hgnitrogen 780 mm Hgargon 780 mm Hg

The partial pressures should always add up to the total pressure and thepercentages should always add up to 100%!

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Problem: Assuming a total pressure of 9.5 atm, what is the partial pressureof each component a the mixture of 98% helium and 2.0% oxygen breathedby deep sea divers?

Problem: Determine the percent composition of air in the lungs from thefollowing composition in partial pressures: Pnitrogen = 573 mm Hg,Poxygen = 100 mm Hg, Pcarbon dioxide = 40 mm Hg, Pwater = 47 mm Hg.

They should add up to 100 (+/- 0.1 for rounding errors.)

Problem: What is the partial pressure of oxygen in the air at an altitudewhere the atmospheric pressure is 685 mm Hg? (Air contains 21% oxygen)(Ans:144 mmHg)

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Chapter 8 Part 2 - Liquids, and Solids8.12 Liquids

Properties of Liquids

Vapor Pressure• Molecules are in constant motion in the liquid state.• If a molecule has enough energy, it can break free of

the liquid and escape into the gas state,called .

• If a liquid is in a closed container, therandom motion of the moleculesoccasionally brings them back into theliquid.

• Evaporation and condensation take placeat the same rate, and the concentration ofvapor in the container is constant.

• is the partial pressure of vapor moleculesin equilibrium with a liquid.

- Vapor pressure depends on bothand of a liquid.

• Liquids with a high vapor pressure evaporate than those with a low vapor pressure.

•

The contribution to the total pressure in the container from the vapormolecules (it’s partial pressure) is referred to as its vapor pressure.

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Effect of Temperature and Pressure

The the temperature, the the vapor pressure.

• When the vapor pressure reaches ,the liquid will .

• If the ambient pressure is , the liquid will boil at atemperature.

• The boiling point when the pressure is 1 atm is the.

ViscosityViscosity is the measure of a liquid's .

1. SI unit - N.s/m2.2. Ease with which molecules move around in the liquid.3. Related to intermolecular forces.- the forces the greater the the viscosity.

Substances such as gasoline (small nonpolar molecules) have low viscosities.Substances such as glycerin (larger more polar molecules) have higher

viscosities.

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Viscosity is the property that is used to rate (SAE 10W40)SAE stands for the Society of Automotive Engineers

Oils meeting the SAE's low temperature requirements have a "W" afterthe viscosity rating (example: 10W), and oils that meet the high ratingshave no letter (example SAE 30).

An oil is rated for viscosity by heating it to a specified temperature, andthen allowing it to flow out of a specifically sized hole. Its viscosityrating is determined by the length of time it takes to flow out of thehole.

If it flows quickly, it gets a viscosity rating.If it flows slowly, it gets a viscosity rating.

Surface TensionThe resistance of a liquid to and increasing its

surface area.1. Due to the difference in intermolecular forces felt by the molecules onthe surface of the liquid and the molecules in the interior of the liquid.

2. Related to intermolecular forces.a. the forces the the surface tension

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Water: A Unique Liquid

Interesting FactsØ Water covers over 70% of the earth’s surface.Ø The human body is made up pf 66% water.Ø Water has the highest specific heat of any liquid.

- It takes a great deal of heat to change the temperature of water.- This makes it easier for our bodies to maintain a steady internal bodytemperature.- This is why climates are more temperate near large bodies of water.

Ø Water also has an unusually high heat of vaporization.This means that it carries away large amounts of heat when itevaporates.

This is how sweating keeps us cool.This is why we get into so much trouble during heat stroke

(we stop sweating.Ø Water is one of the only substances that become less dense when it

freezes.This causes ice to float rather than sink.This keeps our lakes and oceans from freezing solid.

As water freezes, each molecule is locked into position by hydrogen bondingto 4 other molecules. The resulting structure has more open space than liquidwater, accounting for it’s lower density.

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8.13 SolidsKinds of Solids

Crystalline solids –Solids whose atoms, molecules, or ions are rigidly held in an orderedarrangement.- Ionic solids

Particles are . (example: NaCl).Ordered into a 3-D arrangement of alternating + and – ions and

is held together by

- Molecular solidsParticles areheld together by .

(example: sucrose (sugar) or solid dry ice)

- Covalent network solidsParticles arelinked by

into a 3-D array. (eg: diamond or quartz)

- Metallic solidsThey can be viewed as vast three-dimensional arrays of metal cations

immersed in a sea of electrons.o The electron sea acts as

· a glue to hold the cations together and· as a mobile carrier of charge to conduct electricity.

o Bonding attractions extend uniformly in all directions, so· metals are malleable rather than brittle.· When a metal crystal receives a sharp blow, the electron

sea adjusts to the new distribution of cations.

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Amorphous solids

Particles are arranged and have no ordered long-rangestructure. (example: glass, tar, and polymers)

Amorphous solidso soften over a wide temperature range ando shatter to give pieces with curved rather than planar faces

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8.14 Changes of State CalculationsWhen heat is added to a solid, it goes through various changes. The changescan be shown on a heating curve.

Heat of Fusion: The quantity of heat required to completely melt one gramof a substance once it reaches its melting point.Heat of Vaporization: The quantity of heat required to completely vaporizeone gram of a substance once it reaches its boiling point.Formula for determining heat required for melting:

Formula for determining heat required for vaporizing:

Formula for determining heat required to change the temperature of asubstance while keeping the phase constant:

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For all phase change calculations:Mass in gramsT in K or °Cc in cal/ g °C or in J/g °Cheat in cal/g or in J/g

Problem: How much heat (in kcal) is required to take 1.50 mol of solidisopropyl alcohol (rubbing alcohol, mm=60.0 g/mol) at its melting point of-89.5 °C, melt it, raise the liquid to the boiling point of 82.0 °C, and vaporizeall it? (The heat of fusion is 21.4 cal/g, the heat of vaporization is 159 cal/g,and the specific heat of the liquid is 0.641 cal/g °C.)