CHM-4 Phases and Phase Equilibria Flashcards
What are the standard temperature and pressure (STP) values?
0 degrees C
1.00 atm
What is the volume occupied by one mole of gas at STP?
22.4L (Standard Molar Volume)
What are the 5 points of the kinetic molecular theory of gases?
- Gases are composed of extremely small particles seperated by distances which are relatively larger.
- Particles of gas are in constant motion except when they collide
- Particles of an ideal gas do not attract or repel one another
- Collisons do not slow them down, collisions transfer energy to other particles and is not wasted.
- As temperature increases, so does average kinetic energy of the particles.
Which four properties of a gas can 3 be used to calculate the fourth?
Weight (Used to calculate the number of molecules)
Pressure
Volume
Temperature
What is Graham’s Law?
Describes the mean path of a gas particle per unit volume by diffusion and effusion.
What is effusion?
The movement of a gas through a small hole or pore into a vacuum or another gaseous region. If a hole is big enough, it may be considered as diffusion.
What is Charles’ law?
The volume of a gas is directly proportional to the absolute temperature where Pressure and Number of particles are constant.
What is Boyle’s law?
The volume of a fixed weight of gas held at constant temperature varies inversely with pressure.
What is Avogadro’s law?
The volume of a gas at a constant temperature and pressure is directly proportional to the number of particles or moles of gas.
What is ideal gas law?
PV=nRT
What can affect the speed which gas particles move?
Size and mass
What is Miscibility?
The ability of two liquids to mix
Difference between cohesion and adhesion.
Cohesion is how liquids are attracted to each other, whilst adhesion is how liquids are attracted to their surroundings.
What are Van der Waal forces?
Intermolecular forces which hold non-polar molecules together.
(Dipole-dipole, Dipole-induced dipole and London forces).
What are dipole-dipole forces?
Forces which are dependent on orientation and distance of other molecules.
What are dipole-induced dipole forces?
Where a dipolar molecule causes a nonpolar molecule (Such as a noble gas) to become temporarily dipolar by causing movement of electrons in the nonpolar molecule.
The side which the electrons move to make the molecule negative on this side.
What are London forces?
London forces form between nonpolar molecules, where the surrounding negative electrons are attracted to the positive protons of the atom as they move closer together.
When do hydrogen bonds form?
When hydrogen is covalently bonded to O, N or F. Due to the large electronegativity between H and O, N, F.
Intermolecular force occurs between positive hydrogens and negative O, N, F.
Why is water a higher boiling point than that of HF, NH3 or CH3OH? (All hydrogen bonds)
H2O can form 4 hydrogen bonds, meaning it is more efficient.
What are phase changes?
Reversable changes between solid, liquid and gaseuous states.
Name given to the conversion of a liquid into a gas
Vaporisation
Name given to the conversion of a gas into a solid
Deposition
What can be done to increase the rate of Vaporisation?
Increase temperature or reduce pressure
The amount of energy needed to change one mole of substance from Solid > Liquid or Liquid > Gas.
The Molar Heat of Fusion and Molar Heat of Vapourisation
