CHM-4 Phases and Phase Equilibria

Question 1

What are the standard temperature and pressure (STP) values?

Answer 1

0 degrees C

1.00 atm

Question 2

What is the volume occupied by one mole of gas at STP?

Answer 2

22.4L (Standard Molar Volume)

Question 3

What are the 5 points of the kinetic molecular theory of gases?

Answer 3

• 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.

Question 4

Which four properties of a gas can 3 be used to calculate the fourth?

Answer 4

Weight (Used to calculate the number of molecules)
Pressure
Volume
Temperature

Question 5

What is Graham’s Law?

Answer 5

Describes the mean path of a gas particle per unit volume by diffusion and effusion.

Question 6

What is effusion?

Answer 6

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.

Question 7

What is Charles’ law?

Answer 7

The volume of a gas is directly proportional to the absolute temperature where Pressure and Number of particles are constant.

Question 8

What is Boyle’s law?

Answer 8

The volume of a fixed weight of gas held at constant temperature varies inversely with pressure.

Question 9

What is Avogadro’s law?

Answer 9

The volume of a gas at a constant temperature and pressure is directly proportional to the number of particles or moles of gas.

Question 10

What is ideal gas law?

Answer 10

PV=nRT

Question 11

What can affect the speed which gas particles move?

Answer 11

Size and mass

Question 12

What is Miscibility?

Answer 12

The ability of two liquids to mix

Question 13

Difference between cohesion and adhesion.

Answer 13

Cohesion is how liquids are attracted to each other, whilst adhesion is how liquids are attracted to their surroundings.

Question 14

What are Van der Waal forces?

Answer 14

Intermolecular forces which hold non-polar molecules together.
(Dipole-dipole, Dipole-induced dipole and London forces).

Question 15

What are dipole-dipole forces?

Answer 15

Forces which are dependent on orientation and distance of other molecules.

Question 16

What are dipole-induced dipole forces?

Answer 16

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.

Question 17

What are London forces?

Answer 17

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.

Question 18

When do hydrogen bonds form?

Answer 18

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.

Question 19

Why is water a higher boiling point than that of HF, NH3 or CH3OH? (All hydrogen bonds)

Answer 19

H2O can form 4 hydrogen bonds, meaning it is more efficient.

Question 20

What are phase changes?

Answer 20

Reversable changes between solid, liquid and gaseuous states.

Question 21

Name given to the conversion of a liquid into a gas

Answer 21

Vaporisation

Question 22

Name given to the conversion of a gas into a solid

Answer 22

Deposition

Question 23

What can be done to increase the rate of Vaporisation?

Answer 23

Increase temperature or reduce pressure

Question 24

The amount of energy needed to change one mole of substance from Solid > Liquid or Liquid > Gas.

Answer 24

The Molar Heat of Fusion and Molar Heat of Vapourisation