Ch 11 GasesCh 11 Gases

Gases and PressureGases and Pressure

11.111.1

Pressure and ForcePressure and Force

Pressure – (P) the force per unit Pressure – (P) the force per unit area on a surfacearea on a surfacePressure = Pressure = forceforce

areaareaP exerted by a gas depends on …P exerted by a gas depends on …

Volume, ____________, and # of Volume, ____________, and # of moleculesmolecules

ForceForce

SI unit for force is the ________ (N).SI unit for force is the ________ (N).Newton – force that will increase the Newton – force that will increase the

speed of a one kg mass by 1 meter speed of a one kg mass by 1 meter per second for each second the per second for each second the force is appliedforce is applied

What is the force due to gravity?What is the force due to gravity?How does this relate to what your How does this relate to what your

ears do on an airplane?ears do on an airplane?

Measuring PressureMeasuring PressureBarometer – Barometer –

device used to device used to measure measure atmospheric atmospheric pressurepressure

Evangelista Evangelista TorricelliTorricelli

760 mm Hg760 mm Hg

Measuring PressureMeasuring PressureManometer – Manometer –

used to measure used to measure the P of gasesthe P of gases

Hg in one side Hg in one side moves based moves based upon the upon the pressure exerted pressure exerted on the Hgon the Hg

Units of PressureUnits of Pressure

mm Hg – at 0 mm Hg – at 0 °C average °C average atmospheric pressure is 760 mm Hgatmospheric pressure is 760 mm Hg

1 torr = mm Hg Unit named for __.1 torr = mm Hg Unit named for __.1 atmosphere (atm) = 760 mm Hg1 atmosphere (atm) = 760 mm HgThe SI unit for pressure is ________The SI unit for pressure is ________101325 Pa = ___________ kPa 101325 Pa = ___________ kPa 101.325____ = 1____ = 760____ 101.325____ = 1____ = 760____

PascalPascalPascal (Pa) – the pressure exerted Pascal (Pa) – the pressure exerted

by a force of 1 newton (1N) acting by a force of 1 newton (1N) acting on an area of 1 square meteron an area of 1 square meter

Least used in science … PSILeast used in science … PSI1 psi = 6892.86 Pa 1 psi = 6892.86 Pa 1 atm = 14.7 psi1 atm = 14.7 psiSTP = 1 atm & 0STP = 1 atm & 0°C °C KNOW THISKNOW THIS

CalculationsCalculations

Convert 0.83 atm, the atm pressure Convert 0.83 atm, the atm pressure in Denver, to mm Hg and kPain Denver, to mm Hg and kPa

Convert 1.75 atm to kPa and mm HgConvert 1.75 atm to kPa and mm HgConvert 72.7 atm to Pa and torr.Convert 72.7 atm to Pa and torr.

Dalton’s Law of Partial PressureDalton’s Law of Partial Pressure

Partial Pressure – the pressure of Partial Pressure – the pressure of each gas in a mixtureeach gas in a mixture

Dalton’s Law of P.P. – the total P of Dalton’s Law of P.P. – the total P of a gas mix. is the + of the p.p. of the a gas mix. is the + of the p.p. of the component gasescomponent gases

PPTT = P = P11 + P + P22 + P + P33 + … + …Why can u calc the total P of a mix Why can u calc the total P of a mix

by + the p.p of each?by + the p.p of each?

Practice!Practice!

What is the total pressure of a What is the total pressure of a container that has NHcontainer that has NH3(g)3(g) exerting exerting

a pressure of 346 torr,Na pressure of 346 torr,N2(g)2(g)

exerting a pressure of 225 torr, exerting a pressure of 225 torr, and Hand H22O O (g) (g) exerting a pressure of exerting a pressure of

55 torr?55 torr?

PracticePractice

What would be the total pressure What would be the total pressure of a container that is holding of a container that is holding SOSO2(g) 2(g) with a pressure of .385 atm, with a pressure of .385 atm,

SOSO3(g) 3(g) with a pressure of 125 mm with a pressure of 125 mm

Hg, and NHg, and N22OO (g) (g) with a pressure of with a pressure of

5.67 psi? (Answer in atm.)5.67 psi? (Answer in atm.)