Chapter 5 Flashcards
What is pressure?
The result of the collisions between atoms or molecules in a gas and the surfaces around them
What is the formula for finding pressure?
Pressure=Force/Area of surface in which particles collide
What device is used to measure pressure in millimeter of mercury (1 mmHg or 1 torr)
Barometer
What does one average pressure at sea level (atmosphere, atm) equal in mmHG or torr?
1 atm= 760 mmHg
What is one pascal or newton per square meter equal to in atm? (Pa, N/m2)
1 atm= 101 325 Pa
What is one atm in psi?
1 atm=14.7 psi
What are the four basic physical properties of gas?
Pressure P
Volume V
Temperature T
Moles n
What is Boyle’s law about volume and pressure?
Volume and pressure have an inverse relationship
V=constant/P
P1V1=constant=P2V2
P1V1=P2V2
AS LONG AS TEMPERATURE AND MOLES ARE CONSTANT
What does Charles law on volume and temperature state and what formula does it give?
States that volume and temperature have direct proportionality
V=constant x T
V1/T1=V2/T2
AS LONG AS PRESSURE AND AMOUNT OF MOLES ARE CONSTANT
What is avogadros law on volume and number of moles and what equation does it give us?
Linear relationship between volume and number of moles
V= constant x n
V1/n1=V2/n2
AS LOMG AS PRESSURE AND TEMPERATURE STAY CONSTANT
What is an example of avogadros law in real life?
Inflating a balloon
Which each exhale you add more gas particles inside the balloon increasing its volume
You can use avogadros law to calculate the volume of a gas following a change in the amount of gas
What equation does the ideal gas law give us?
Putting everything together we get
V= constant (nT/P)
V= RnT/P
PV= nRT
What is gay-lussac’s law and what equation does it give us?
P= constant x T
P1/T1=P2/T2
What is the difference between total pressure and gauge pressure?
Gauge pressure is the difference between the total pressure and atmospheric pressure
What is molar volume?
What is volume at STP?
The volume occupied by one mole of a substance
STP- 273.15 K and 1.00 atm
Standard temperature and pressure
22.4L
What is the formula for density with a gas under standard temperature and pressure?
Density= molar mass/ molar volume (22.4L)
The density of a gas is directly proportional to its molar mass
D= PM(molar mass)/RT
What is partial pressure (Pn)?
What is it’s formula?
Partial pressure is the pressure due to any individual component in a gas mixture
Pn=nn(RT/V)
How can you find the total pressure in a mixture of gases?
Ptotal=(n1+n2+n3+…)(RT/V)
How can we find the mole fraction (Xa) of a mixture of gases? How can we use the mole fraction in an equation the find the partial pressure?
Xa=na/ntotal
Pa=XaPtotal
How do scientists collect gas?
They set up an apparatus for the displacement of water, they force the gas into a device with water so the gas bubbles through it into a flask where it is trapped
What is vapour pressure? How does vapour pressure change with temperature?
The partial pressure of water in the resulting mixture after gas has been displaced when collecting gas
Temperature goes up, vapour pressure goes up
How do we use stoichemetry in gases? What equation etc
Find numbers of moles using
n=PV/RT
Use mole ratiosi
What are the three points of the kinetic molecular theory?
- The size of a particle is negligibly small- assumes particles occupy no volume
- The average kinetic energy of a particle is proportional to the temperature in kelvin’s
- The collision of one particle with another (or with walls) is completely elastic- means when particles collide they may exchange energy and but there is no loss of energy
What equation shows that the kinetic energy of a particle depends on its mass and velocity? How do light particles travel in difference of speed of heavier ones at a given temp?
KE=1/2mv^2
In a gas mixture at a given temperature, lighter particles travel faster (on average) than heavier ones
When are the two instances that gases behave ideally? (Both instances must be true)
A. The volume of the gas particles is negligible compared to the space between them
B. The forces between the gas particles are not significant
When does the finite volume of gas particles become important?
It becomes important at high pressure, when the particles themselves occupy a significant portion of the total gas volume
What is the corrected ideal gas equation for real gases?
V=nRT/p + nb
Where n is the number of moles and b is a constant that depends on the gas
(V-nb) = nRT/P
What are intermolecular forces?
The attractions between the atoms or molecules in a gas
They are small and therefore do not matter much at low pressure
Don’t matter at high temps either because the molecules have a lot of kinetic energy
What is the corrected ideal gas equation for intermolecular forces?
P=nRT/V - a(n/V)^2
Where a is a constant that depends on the gas
What is Van der Waals equation?
The equation that describes non ideal gas behaviour
(P+a(n/V)^2) x (V-nb) = nRT
