9-11 Flashcards
Pressure (P)
The force per unit area measured in SI units of pascals
Atmospheric pressure
The force per unit area exerted by air on all objects, measured in kilopascals (kPa)
Standard pressure (at sea level)
Average pressure is 101 kPa, is equal to 1 standard atmosphere (1 atm)
Standard Temperature and Pressure (STP)
0 degrees Celsius and 1 atm (101.325 kPa), standard conditions for working with gases (not convenient)
Standard Ambient Pressure (SATP)
Defined at 25 degrees Celsius and 100 kPa, this standard is much closer to laboratory conditions (more convenient)
SI and Non-SI Units of Gas Pressure
Pascal (SI unit) =1 Pa=1N/m^2
Atmosphere=1 atm= 101.325 kPa
Millimetres of mercury= 760mmHg=1 atm= 101.325kPa
Torricelli= 1 torr= 1 mm Hg
Relationship between Pressure and Volume
Inverse variation between pressure and volume of a gas, as pressure increases the volume decreases
Boyles Law Equation
P1V1 = P2V2
When temperature and amount of gas are held constant
Boyle’s Law States
As the pressure on a gas increases, the volume of the gas decreases proportionally provided that the temperature and chemical amount of gas remains constant
Absolute Zero
If using the Celsius scale, crosses x axis at -273 degrees Celsius. It is the lowest possible temperature
Absolute (kelvin) Temperature Scale
Absolute zero is the basis for this temperature scale
(-273 Celsius) = (0K)
Convert Celsius to kelvin = + 273
Convert kelvin to Celsius= - 273
Kelvin Scale STP and SATP
STP: 273.15 K and 101.325 kPa
SATP: 298.15 K and 100 kPa
Charles Law Equation
V1/T1 = V2/T2
Valid when pressure and amount of gas are held constant
Relationship between temperature and volume
As temperature increases the volume increases
Charles Law states that
As the temperature of a gas increases, the volume increases proportionally provided that the pressure and chemical amount of gas remains constant
Combined gas Law Equation
P1V1/T1 = P2V2/T2
Combined gas Law states
The product of the pressure and volume of a gas sample is proportional to its absolute temperature in kelvin
Kinetic molecular theory explains:
- why gases are compressible
- the concept of gas pressure
- explains Boyles law
- explains Charles Law
Explaining Law of combining volumes (Gay-Lussacs law)
States that when measured at the same temperature and pressure, volumes of gaseous reactants and products of chemical reactions are always in simple ratios of whole numbers
Avogadros Theory
Relationship between volume ratios and coefficient ratios, proposed equal volumes of gases at the same temperature and pressure contain equal numbers of molecules
*must be at the same temperature and pressure
Molar Volume of Gases
Is the volume that one mole of a gas occupies at a specified temperature and pressure (Vm)
Molar Volume of Gas at SATP and STP
SATP: 24.8L/mol
STP: 22.4 L/mol
Relationship of chemical amount (n) volume (V) and molar Volume (Vm)
n=V/Vm
V=n•Vm
Ideal gas Law Equation
PV = nRT
Ideal Gas law states
Is a hypothetical Gas that obeys all the gas laws perfectly under all conditions, it does not condense into a liquid when cooled, and graphs of its volume and temperature and of pressure and temperature perfectly straight lines
STP and SATP conditions real gases behave like ideal gases
Ideal gas Law universal gas constant
R= 8.314 kPa•L / mol•K
Physical properties of gases
Gases have no shape or volume if their own, they assume the shape and volume of their container
Gases are highly compressible
Gases diffuse or spread out, occupying all space that is available to them
Gases mix readily with other gases
Temperature
Is a measurement of the amount of kinetic energy (molecular motion) a sample has
Higher temperature = greater molecular motion
