Ch 11 Gases and Pressure 11 1 Pressure

Ch 11 Gases and Pressure 11. 1

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

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

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

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

Units of Pressure l mm Hg – at 0 °C average atmospheric pressure is 760 mm Hg l 1 torr = mm Hg Unit named for __. l 1 atmosphere (atm) = 760 mm Hg l The SI unit for pressure is ____ l 101325 Pa = ______ k. Pa l 101. 325____ = 1____ = 760____

Pascal l Pascal (Pa) – the pressure exerted by a force of 1 newton (1 N) acting on an area of 1 square meter l Least used in science … PSI l 1 psi = 6892. 86 Pa l 1 atm = 14. 7 psi l STP = 1 atm & 0°C KNOW THIS

Calculations l Convert 0. 83 atm, the atm pressure in Denver, to mm Hg and k. Pa l Convert 1. 75 atm to k. Pa and mm Hg l Convert 72. 7 atm to Pa and torr.

Dalton’s Law of Partial Pressure l Partial Pressure – the pressure of each gas in a mixture l Dalton’s Law of P. P. – the total P of a gas mix. is the + of the p. p. of the component gases l PT = P 1 + P 2 + P 3 + … l Why can u calc the total P of a mix by + the p. p of each?

Practice! l 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 l 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. )