Chapter 8 Section 1 Describing Chemical Reactions p. 261-275 1 Gases Chapter 10/11 Modern Chemistry...

Chapter 8 Section 1 Describing Chemical Reactions p. 261-275

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GasesChapter 10/11Modern Chemistry

Sections 10.1, 11.1-11.3Sections 10.1, 11.1-11.3The Kinetic Molecular Theory of MatterThe Kinetic Molecular Theory of Matter

Gases and PressureGases and PressureThe Gas LawsThe Gas Laws

Gas Volumes and the Ideal Gas LawGas Volumes and the Ideal Gas Law

Chapter 11Section 1 Gases & Pressure p. 361-368

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Gases and Pressure

Section 11.1Section 11.1


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• Pressure = force (in Newtons) per unit area

• Pressure of a gas is caused by particles of a gas colliding with the walls of its container

• Pressure (P) of a gas depends on volume (V), temperature (T), and the number of particles (n).

PressurePressure


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Insert Holt Visualizing Matter Disc 2


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• The atmosphere exerts pressure.• 78% N, 21% O, 1% other• Atmospheric pressure is the sum of the

individual pressures of the gases.

Atomospheric PressureAtomospheric Pressure


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Measuring PressureMeasuring Pressure

p. 363

• Barometer: a device used to measure atmospheric pressure.

• Developed by Evangelista Torricelli in the early 1600s.


7p. 363Merc

ury

Baro

mete

rM

erc

ury

Baro

mete

r


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Aneroid BarometerAneroid Barometer

The aneroid barometer is operated by a metal cell containing only a very small amount of air, or a series of such cells joined together. Increased air pressure causes the sides of the cell or cells to come closer together. One side is fixed to the base of the instrument while the other is connected by means of a system of levers and pulleys to a rotating pointer that moves over a scale on the face of the instrument.

http://www.stuffintheair.com/Gulf-Jet-Stream.html


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Measuring PressureMeasuring Pressure

• A manometer measures the pressure of a gas in a flask.

p. 363


10Manom

ete

rM

anom

ete

r


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The average atmospheric pressure at sea level at 0°C.

•760 mm Hg – millimeters of mercury

•1.00 atm – atmospheres•101.325 kPa – kilopascals (SI Units)

1 pascal is the pressure exerted by a force of 1 Newton acting on an area of 1 square meter

See the table on page 364

Units of PressureUnits of Pressure

Chapter 11 Section 1 Gases & Pressure p. 361-368

12p. 364

Table 1 Units of PressureTable 1 Units of Pressure


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• The average atmospheric pressure in Denver, Colorado, is 0.830 atm. Express this pressure in

(a) millimeters of mercury (mm Hg) and (b) kilopascals (kPa).

p. 3

65

a. 631 mm Hg b. 84.1 kPa

Converting Pressure UnitsConverting Pressure Units


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1. Convert a pressure of 1.75 atm to kPa and to mm Hg.

2. The critical pressure of carbon dioxide is 72.7 atm. What is this value in units of pascals?

p. 3

65

1.177 kPa, 1330 mm Hg

2. 7.37 106 Pa

Practice Problems p. 365Practice Problems p. 365


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• Partial Pressure: The pressure of each gas in a mixture

• Dalton’s Law of Partial Pressures: The total pressure of a gas mixture is the sum of the partial pressures of the component gases.

Dalton’s Law of Partial Dalton’s Law of Partial PressuresPressures

PT = p1 + p2 + p3 …


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17p. 363Law

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Gases Collected by Water DisplacementGases Collected by Water Displacement

p. 366


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• A gas collected over water is a mixture of the gas and water vapor

• The pressure water exerts is called vapor pressure


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• When the water levels inside and outside the tube are the same the PT = Patm

Patm = pgas + pH2O

orpgas = Patm - pH2O


PT>Patm

PT=Patm

PT<Patmatm

atm

atm

atm


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• The vapor pressure of water varies with temp.


p. 8

59


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• Oxygen gas from the decomposition of potassium chlorate, KClO3, was collected by water displacement. The barometric pressure and the temperature during the experiment were 731.0 mm Hg and 20.0°C, respectively. What was the partial pressure of the oxygen collected?

p. 3

67

1. 713.5 mm Hg

Dalton’s Law ProblemsDalton’s Law Problems


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1. Some hydrogen gas is collected over water at 20.0°C.The levels of water inside and outside the gas-collection bottle are the same. The partial pressure of hydrogen is 742.5 mm Hg.What is the barometric pressure at the time the gas is collected?

p. 3

67

1. 760.0 mm Hg

Practice Problems p. 367Practice Problems p. 367

Chapter 11 Section 2 The Gas Laws p. 369-377

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Boyle’s LawBoyle’s Law


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• P & V relationship; n & T held constant• “The volume of a fixed mass of gas

varies inversely with the pressure at constant temperature.”


Insert Glencoe Chemistry Matter Disc 2

p. 369


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PV = kk is a constant

P1 V1 = k

P2 V2 = k

P1 V1 = P2 V2


P1

P2

V1

V2

p. 370


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1. A sample of oxygen gas has a volume of 150.0 mL when its pressure is 0.947 atm. What will the volume of the gas be at a pressure of 0.987 atm if the temperature remains constant?

p. 3

70

1. 144 mL O2

Boyle’s Law ProblemBoyle’s Law Problem


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Charles’ LawCharles’ Law


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• Same size degrees as the Celcius scale

• 0 K = -273.15° C

• 0 K = absolute zero

• K = 273 + °C

Kelvin Temperature ScaleKelvin Temperature Scale


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• V & T relationship; n & P held constant• The volume of a fixed mass of gas at

constant pressure varies directly with the Kelvin temperature.”


Insert Glencoe Chemistry Matter Disc 2


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V / T = k k = a constant

V1 / T1 = k

V2 / T2 = k

V1 = V2

T1 = T2


p. 372

T1 T2

V1

V2


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1. A sample of neon gas occupies a volume of 752 mL at 25°C. What volume will the gas occupy at 50°C if the pressure remains constant?

p. 3

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1. 815 mL Ne

Charles’ Law ProblemCharles’ Law Problem


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Combined Gas LawCombined Gas Law


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• P, V and T relationship; n held constant• “The combined gas law expresses the

relationship between pressure, volume and temperature of a fixed amount of gas.”

Combined Gas LawCombined Gas Law


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Standard Temperature and PressureStandard Pressure

1.00 atm760 mm Hg101.325 kPa

Standard Temperature273 K0° C

STPSTP


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1. A helium-filled balloon has a volume of 50.0 L at 25°C and 1.08 atm. What volume will it have at 0.855 atm and 10.0°C?

p. 3

75

1. 60.0 L He

Combined Gas Law ProblemsCombined Gas Law Problems

Chapter 8 Section 1 Describing Chemical Reactions p. 261-275 1 Gases Chapter 10/11 Modern Chemistry...

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