Chapter

11

Gases

Pressure and Force

____________ (P): the force per _________ on a surface.

________ (N): the force that will increase the speed of a ___________ by _____________ each second the force is applied.

___________: a device used to measure ______________ pressure.

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Units of Pressure

Millimeters of Mercury: _________ = 1 torrAtmosphere: _______ = 760 mm HgPascal: the pressure exerted by a force of _________ acting on an area of _____________. 1 atm = 1.01325 x 105 Pa

1 atm = 101.325 KPa______: standard temperature and pressure, 0oC and 1 atm.Pounds per Square Inch (psi): 1 atm = ________

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Practice

Ex. The barometer reads 758 mm Hg. What is the ________________________ in Pa?

758 mm Hg x 1.01325 x 105 Pa = 1.01 x 105 Pa 760 mm Hg

1) The air pressure in a tire is 109 kPa. What is the pressure in atm?

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Dalton’s Law

________________: the pressure of each gas in a mixture of gases.

_____________: the ___________ of a gas mixture is the ______________________ of

the component gases.

PT = P1 + P2 + P3 …

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Boyle’s Law_______________: the volume of a fixed mass of gas varies inversely with the pressure at constant temperature.

_________________Ex. A gas occupies a volume of ________ at a pressure of ________ and temp. _______. When the pressure is changed, the volume becomes _______. If there is no change in temp., what is the new pressure?

(1.01 KPa) (458 ml) = P2 (477 ml)

P2 = 0.970 kPa11-6

PracticeP1V1 = P2V2

2) A gas occupies a volume of 2.45L at a pressure of 1.03 atm and temp. 293 K. What volume will the gas occupy if the pressure changes to 0.980 atm and the temp. remains the same?

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Charles’s Law_____________: the given value of zero in the Kelvin temperature scale. K = 273.15 + oC

_____________: the volume of a fixed mass of gas at constant pressure varies directly with the ______________.

__________Ex. What will be the volume of a gas sample at ________ if it’s volume at __________? Assume that the pressure is constant.

3.42L = V2

215K 309K

V2 = 4.92L

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Practice3) A gas sample at 83oC occupies a volume of

1400m3. At what temperature will it occupy 1200m3? Assume that the pressure is

constant.

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Gay-Lussac’s Law______________: the pressure of a fixed mass of gas at constant volume varies directly with the ______________.

P1 = P2

T1 T2Ex. The gas in a container is at a pressure of __________ at __________. Directions on the container warn the user not the keep it in a place where the temp exceeds ________. What would the pressure in the container be at 52oC?

3.00 atm = P2

298K 325K

P2 = 3.27 atm

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Practice

P1 = P2

T1 T2

4) At 120oC the pressure of a sample of nitrogen is 1.07 atm, What will the pressure be at 205oC, assuming constant volume?

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Combined Gas Law

P1 V1 = P2 V2

T1 T2____________________: expresses the relationship between pressure, volume and temp (K) of a fixed amount of gas.

Ex. A helium balloon has a volume of ________________ and _________. What volume will it have at _______________?

(1.08 atm)(50.0L) = (0.855 atm) V2

298 K 283 K

V2 = 60. L

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Gas Volumes

______________________________________: at a constant temp and pressure, the ___________ of gaseous reactants and products can be expressed as ratios of small whole numbers. (____________ in balanced eq. can represent ______________!)

_________________: equal volumes of gases at the same temp. and pressure contain equal numbers of molecules.

___________

Volume = k(constant) x n(moles)

_____________________: the volume occupied by one mole of a gas at STP is 22.4L.

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PracticeEx. What volume does 0.0685 mol of gas occupy at STP?

0.0685 mol x 22.4 L = 1.53 L

1 mol

Ex. What quantity of gas, in moles, is contained in 2.21 L at STP?

2.21L x 1 mol = 0.0987 mol

22.4 L

5) At STP, what is the volume of 7.08 mol of nitrogen gas?

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Gas StoichGiven a volume, find a volume:

Ex. When ________ of hydrogen reacts with bromine, what volume of HBr is produced?

_________________

0.75L H2 x 2L HBr =1.5L HBr

1L H2

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Practice6) What volumes of sulfur dioxide and dihydrogen sulfide gases are necessary to

produce 11.4 L of water vapor?

11-16

Gas StoichEx. How many liters of CO2 are produced at STP

when 400.00g of CaCO3 react with HCl?

CaCO3 + HCl → CaCl2 + CO2 + H2O

________________________________

400.00g CaCO3 x 1mol CaCO3 x 1mol CO2 x 22.4L

100.04g CaCO3 1mol CaCO3 1mol CO2

= ______________

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Gas StoichEx. Find the mass of sugar required to produce __________ at

STP in the rxn:

C6H12O6 → 2C2H6O + 2 CO2

1.82L CO2 x 1mol CO2 x 1molC2H12O6 x 180.18gC6H12O6

22.4L 2mol CO2 1 mol

= ____________________

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Ideal Gas Law_____________: the mathematical relationship

among pressure, volume, temperature and the number of moles of a gas.

Ideal Gas Law:

______________

How R (the ideal gas law constant) is derived:

R = (1 atm)(22.4L) = _________________ (1 mol)(273K)

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Ideal Gas LawEx. If the pressure exerted by a gas at ____ in

a volume of ______________, how many moles of gas are present?

(5.00atm)(0.0010L) = n(0.0821atmL/molK)(273K)

n = __________________

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Practice7) What volume would be occupied by 100. g

of oxygen gas at a pressure of 1.50 atm and a temp. of 25oC?

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Diffusion and Effusion____________________: rates of effusion of

gases at the same temperature and pressure are __________________ to the _______________ of their molar masses.

rate of effusion of A = √MB

rate of effusion of B √MA

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Diffusion and Effusion

rate of effusion of A = √MB

rate of effusion of B √MA

Ex. Compare the rate of effusion of hydrogen and oxygen at the same temp. and pressure.

rate of effusion of H2 = √32.00 g/mol = 3.98

rate of effusion of O2 √2.02 g/mol

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Ch. 11TheEnd!

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