Ch 11 Gases Gases and Pressure 11.1

Pressure and Force Pressure – (P) the force per unit area on a surface Pressure – (P) the force per unit area on a surface Pressure = force Pressure = force area area P exerted by a gas depends on … P exerted by a gas depends on … Volume, ____________, and # of molecules Volume, ____________, and # of molecules

Force SI unit for force is the ________ (N). SI unit for force is the ________ (N). Newton – force that will increase the speed of a one kg mass by 1 meter per second for each second the force is applied Newton – force that will increase the speed of a one kg mass by 1 meter per second for each second the force is applied What is the force due to gravity? What is the force due to gravity? How does this relate to what your ears do on an airplane? How does this relate to what your ears do on an airplane?

Measuring Pressure Barometer – device used to measure atmospheric pressure Barometer – device used to measure atmospheric pressure Evangelista Torricelli Evangelista Torricelli 760 mm Hg 760 mm Hg

Measuring Pressure Manometer – used to measure the P of gases Manometer – used to measure the P of gases Hg in one side moves based upon the pressure exerted on the Hg Hg in one side moves based upon the pressure exerted on the Hg

Units of Pressure mm Hg – at 0 °C average atmospheric pressure is 760 mm Hg mm Hg – at 0 °C average atmospheric pressure is 760 mm Hg 1 torr = mm Hg Unit named for __. 1 torr = mm Hg Unit named for __. 1 atmosphere (atm) = 760 mm Hg 1 atmosphere (atm) = 760 mm Hg The SI unit for pressure is ________ The SI unit for pressure is ________ Pa = ___________ kPa Pa = ___________ kPa ____ = 1____ = 760____ ____ = 1____ = 760____

Pascal Pascal (Pa) – the pressure exerted by a force of 1 newton (1N) acting on an area of 1 square meter Least used in science … PSI 1 psi = Pa 1 atm = 14.7 psi STP = 1 atm & 0°C KNOW THIS

Calculations Convert 0.83 atm, the atm pressure in Denver, to mm Hg and kPa Convert 0.83 atm, the atm pressure in Denver, to mm Hg and kPa Convert 1.75 atm to kPa and mm Hg Convert 1.75 atm to kPa and mm Hg Convert 72.7 atm to Pa and torr. Convert 72.7 atm to Pa and torr.

Dalton’s Law of Partial Pressure Partial Pressure – the pressure of each gas in a mixture Partial Pressure – the pressure of each gas in a mixture Dalton’s Law of P.P. – the total P of a gas mix. is the + of the p.p. of the component gases Dalton’s Law of P.P. – the total P of a gas mix. is the + of the p.p. of the component gases P T = P 1 + P 2 + P 3 + … P T = P 1 + P 2 + P 3 + … Why can u calc the total P of a mix by + the p.p of each? Why can u calc the total P of a mix by + the p.p of each?

Practice! What is the total pressure of a container that has NH 3(g) exerting a pressure of 346 torr,N 2(g) exerting a pressure of 225 torr, and H 2 O (g) exerting a pressure of 55 torr? What is the total pressure of a container that has NH 3(g) exerting a pressure of 346 torr,N 2(g) exerting a pressure of 225 torr, and H 2 O (g) exerting a pressure of 55 torr?

Practice What would be the total pressure of a container that is holding SO 2(g) with a pressure of.385 atm, SO 3(g) with a pressure of 125 mm Hg, and N 2 O (g) with a pressure of 5.67 psi? (Answer in atm.) What would be the total pressure of a container that is holding SO 2(g) with a pressure of.385 atm, SO 3(g) with a pressure of 125 mm Hg, and N 2 O (g) with a pressure of 5.67 psi? (Answer in atm.)