Ch 11 Section 1 Flashcards
the pressure increase is caused by the increase in the number of ….. with the inside walls o the tire
collisions of molecules of air
the collisions cause an outward… against the inside walls
push, or force
gas molecules exert …. on any surface with which they…
pressure; collide
the pressure exerted by a gas depends on
volume, temperature, and the number of molecules present
pressure is defined as the ….. on a surface
force per unit area
Pressure =
force/ area
SI unit for force is
newton
newton is the force that will increase the speed of a … by …. each … that the …
one-kilogram mass; one meter per second; second; force is applied
at earth’s surface, gravity has an acceleration of
9.8 m/ s^2
The atmosphere exerts
pressure
The pressure of the atmosphere can be thought of as caused by the weight of the …. that
gases; compose the atmosphere
the atmospheric pressure at sea level is eqaul to the weight of a …. mass per square centimeter of surface
1.03 kg
the atmosphere contains about…. nitrogen, …. oxygen, and … other gases, including…
78%; 21%; 1%; argon and carbon dioxide
atmospheric pressure is the sum of the individual pressures of the
various gases in the atmosphere
a barometer is a device used to measure
atmospheric pressure
first type of barometer was introduced by… during the early …
Evangelista Torricelli; 1600s
the mercury in the tube pushes downward because fo
gravitational for e
the column of mercury in the tube s stopped from falling beyond a certain point because the atmosphere exerts a … on the surface of the mercury outside the tube
pressure
this pressure is transmitted through the fluid mercury and is exerted
upward on the column of mercury
the mercury in the tube falls only until the pressure exerted by its weight is equal to the ….
pressure exerted by the atmosphere
the exact height of the mercury in the tube depends on the
atmospheric pressure, or force per unit area
th pressure is measured in terms of the mercur column’s … in the barometer tube
height
from experiments like Torricelli’s it’s known that at sea level and at 0 degrees C the average pressure of the atmosphere can support a
760 mm column of mercury
the atmospheric pressure at any given place depends on the
elevation and the weather conditions
if the atmospheric pressure is greater than the average at sea level, the height of the mercury column in a barometer will be
greater than 760 mm and vice versa
all gases exert
pressure
a device called a manometer can be used to measure the pressure of an
enclosed gas sample
the difference in the height of mercury in the two arms of the U-tube is a measure of the
oxygen gas presure in the container
because atmospheric pressure is often measured by a mercury barometer, pressure can be expressed in terms of the
height of a mercury’s column
thus, the common unit of pressure is
millimeters of mercury (mm Hg)
a pressure of 1 mm Hg is also called
1 torr
the average atmospheric pressure at sea level at 0 degrees C is
760 mm HG
One atmosphere of pressure is defined as being exactly equivalent to
760 mm Hg
In SI, pressure is expressed in derived units called
pascals
one pascal is defined as the pressure exerted by a force of one
newton acting on an area of one square meter
it’s more convenient to express pressure in
kilopascals
standard atmosphere is equal to
1.01325 x 10^5 Pa, or 101.326 kPa
to compare volumes of gases, one must know the
temperature and pressure at which the volumes are measured
for purposes of comparision, scientists have agreed on standard conditions of exactly
1 atm pressure and 0 degrees C
1 atm pressure and 0 degrees C are called
standard temperature and pressure
the pressure exerted by each gas in an unreactve mixture is independent of that exerted by
other gases present
the pressure of each gas in a mixture is called the
partial pressure of that gas
dalton’s law of partial reassures states that the total pressure of a gas mixture is the sum of the
partial pressures of the component gases
dalton’s law: Pt=
P1 + P2 + P3
each of the rapidly moving particles of gases in a mixture has an equal chance to
collide with the container walls
therefore each gas exerts a pressure indepedent of that exerted by the
other gases pressent
the total pressure is the result of the total number of collisions per
unit of wall area in a given time
gases produced in the lab are ften collected over
water
the gas produced by the reaction displaces the water, which is more dense, in the
collection bottle
a gas collected by water displacement is not pure but is always mixed with
water vapor
that is because water molecules at the liquid surface
evaporate and mix with the gas molecules
water vapor like other gases exerts a pressure known as
vapor pressure
Patm =
Pgas + PH2O
to find the partial pressure of the dry gas collected you would subtract the pressure of the water vapor at the given temperature from the
total pressure
the vapor pressure of water varies with
temperature
