FINAL Chapter 4/11 Flashcards
(12 cards)
Why does NH3 have a larger a value in the van der Waals equation, (P+n2a/V2
)(V-nb) = nRT
also explain the correction factors and variables
a is the correction for intermolecular forces and since NH3 can H bond it has stronger IMF than H2 which cannot H bond
a and b are gas specific
a - “attractive force” corrects for intermolecular forces between gas particles, causes real gas pressure to be less than ideal
b - corrects for molar volume of gas molecule, which causes real gas volume to be greater than ideal gas volume
**general trend but not strict rule that higher molar masses have higher molar volume but it depends on density
additional variables of n and v needed to cancel out units of a and b
One container of H2 and the other of NH3. Which container is the average kinetic energy and velocity the greatest
Average KE is the same in both since kinetic energy is temperature dependent
Ke = 1/2mv^2 so velocity must be higher with the lighter gas since mass and velocity are inversely proportional
What does Graham’s law about the rate of effusion say about which gas will diffuse quicker?
The one with the lower molar mass since rate of effusion is inversely proportional to molar mass
r1/r2 = sqrt(M2/M1)
This can be explained by the equation KE = 1/2mv^2
Define polariziability and what kinds of atoms have higher polariziability
How easily electron cloud is distorted by other ions or dipoles, to cause induced dipole
Heavier, larger, and negative ions are more polarizable becuase electrons held less tightly to nucleus
negative ions have greater repulsion so they are more inclined to lose an electron
Avogardro’s principle
Equal volumes of gases at the same temperature and pressure will contain equal number of molecules (even when they are different gases!)
Does weaker IMF cause lower or higher vapour pressure?
Causes higher vaporu pressure becuase weak IMF make it easy for molecules to escape and hence more molecules can evaporate, leading to a higher pressure, but low heat of vapourization
What does the ideal gas law asssume about the gas?
Gas particles have no volume and do not interaction with each other except for collisions
Equation for partial pressure of A
pA = xA + pT
where xA is the mole fraction and pT is the partial pressure
Define Diffusion
random motion of particles from high concentration/pressure to low
Define Effusion
Process by which gas particles escape through small opening in evacuated chamber
What conditions are teh van der waals equations used for?
non ideal for high pressure (volume and IMF) and low temp (IMF)
The fact that volume does count and there is repulsion
at high pressure volume no longer becomes negliable
at low temperatures gases can slow down in speed and attract and repel
How to know which R value to use?
With gases or ideal gas laws you use
0.08206 usually
And with energy you use 8.314i
