Gases Ch 6 Flashcards
(55 cards)
Elements that exist as gases at 25 degrees Celsius and 1 atmosphere
Some substances found as gases at 1atm and 25degrees Celsius
H N O F Cl He Ne Ar Kr Xe Rn
Name some physical Characteristics of Gases
What is air made up of?
N2 78%
O2 21%
CO2—->
H2O — > these 3 total to 1% trace amnts
Ar——->^
Gas Pressure Unit Conversions
760mm Hg (Mercury) =
760 torr =
1 atmosphere =
1.01x10^5 Pascals
What is the pressure in atm if the barometer reading is 688 mm Hg?
688mm Hg
————————— = .905 atmospheres
760 mm Hg (per atm)
Who invented the barometer and what year?
Evangelists Torricelli in 1643
—Mercury always rose to
760mm at sea level
— Defined standard atmospheric pressure: 760mm High at 0 deg C at sea
level
Pressure of a Gas in Barometer
Another example of atmospheric pressure in play would be:
Drinking through a straw:
— suck out air
— pressure in straw is lowered
— atmospheric pressure remains
constant
— a vacuum is created and the liquid rushes into the straw to replace air sucked out & to equalize the pressure
What is used to measure pressure of a gas > or = to atmospheric pressure?
An OPEN-TUBE Manometer
h + atm pressure = pressure of gas
— the difference in height (h) of the 2 levels plus the atm pressure = pressure of the gas
What is used to measure the PRESSURE of a GAS other than atmospheric pressure?
For PRESSURES < Atmospheric Pressure
CLOSED-TUBE Manometer
h = the pressure of the gas
H is the difference in height between the 2 levels on the closed-tube manometer
Boyle’s Law
Pressure = 1/Volume X K
P proportional to 1/V
Or P = 1/V*k
PV=k
Apparatus for studying the relationship between Pressure & Volume of a Gas
Add mercury, gas volume decreases
The J-Tube
As
P(h)-(mercury level) {on right} increases,
Volume of gas {on left} decreases
{inside the J Tube}
Inversely related
As 1 increases,
the other decreases
Boyle’s Law
P1V1=P2V2
Pressure “proportional to” 1/Volume
Pressure x Volume= a constant rate of change
0.6atm x 2L volume = 1.2
0.3atm x 4L volume = 1.2 constant rate
Pressure x Volume = Constant
So Boyle’s Law States
P1V1=P2V2
A sample of chlorine gas occupies a volume of 946 mL at a pressure of
726mm Hg, what is the pressure of the gas (in mm Hg) if the volume is reduced at constant temperature to 154 mL?
4460 mm Hg
The Temp-Vol relationship was created by ?
Jacques Charles & Joseph Gay Lussac
It is called Charle’s Law
What does Charles Law State?
Volume increases@constant rate of temp
V/T=V/T
Direct Relationship Temp ^ Volume ^
“The volume of a fixed amount of gas at constant pressure is directly proportional to the absolute temperature (in Kelvin) of a gas”
As Gas temperature increases, gas Volume increases proportionally as stated by ?
Charles & Gay-Lussac’s Law
The amount of mercury (shows constant pressure amount) which gets pushed up as the volume increases raising the temp reading a direct proportional amount to the increase in volume so if volume goes up 75%, temp goes up 75%
Charles’s and Gay-Lussac’s Law
Volume =k+temp (where k is constant)
Volume proportional to temp
V1 = V2
—- —— Temp must be in Kelvin
T1 T2 T (k)= T(Celsius)+273.15
The slope = the slope
What is the lowest theoretically attained temperature?
Who invented it and what year?
-273 degrees Celsius
Lord Kelvin called it absolute zero in 1848
Each gas converged at the same -273C=0K —- regardless of pressure
A sample of carbon monoxide Gas occupies 3.20 L at 125°C, at what temperature will the gas occupy a volume of 1.54 L if the pressure remains constant?
First convert Celsius to Kelvin!
V1/T1=V2/T2 use Kelvin temp c+273
3.20L/398.15k = 1.54L/?
1.54L x 398.15/3.20L=192K
Volume-Amount Relationship :
Avogadro’s Law states?
“At constant temperature and pressure, the volume of gas is directly proportional to the amount (moles) of gas”
TP=held constant
Volume & # of moles chng proportionally
n^v^
Avogadro’s Law
Volume proportional to moles (n)
V= constant x n (constant = k = slope)
Volume/moles=volume/moles
Constant temp constant pressure
