CHEM 120 MIDTERM EXAM 1
1. Newton's laws of motion
Answer:
- particles in random straight-lone motion
- separated by large distances so brief collisions
- no long range forces
- gas has internal energy only due to kinetic energy of particles
- total energy is constant
2. microscopic description of pressure
Answer: P = (1/3)(N/V) m u^2
- N = nb of particles
- m = mass of 1 particle
- u^2 = average square velocity
3. Root mean square velocity (Urms)
Answer: - close to average speed of the particles
4. Total kinetic energy
Answer: Ek = 1/2 m u^2
5. Graham's law of effusion
Answer:
- effusion - process by which a gas escapes througha tiny hole in its container into an
evacuated space
- law: rate of effusion of a gas is inversely proportional to the square root of its molar
mass
- rate of diffusion (movement of 1 gas through another) is the same way but diffusion
rates lower because gas molecule hits many other molecules (diffusion is slower)
6. Mean free path
Answer:
- average distance a molecule travels between collisions at agiven temperature and
pressure
- key factor in rate of diffusion and rate of heat flow through a gas
,7. Collision frequency
Answer:
- divide most probable speed (m/s) by the mean free path(m/collision)
- average nb of collisions per second that each particle undergoes
8. Effect of inter particle attractions
Answer:
- as p(ext) rises, volume decreases andparticles get closer so inter particle attraction
has a greater effect
- results in decreased gas pressure and so a smaller numerator in PV/RT
9. Effect of particle volume
Answer:
- at extremely high pressures, the space taken up butthe particles makes the free
volume less than the container volume
- causes numerator and so ratio to become very high in PV/RT
10. Van der waals equation
Answer:
- adjust p up by adding a factor accounting for interparticle attractions
- adjust v down bu subtracting a factor accounting for particle volume
- a and b are constants
- a depends on nb and distribution of electrons, relating to complexity of a particle
and the strength of its inter particle attraction
- b relates to the volume of the particle
11. Redlich Kwong model
Answer: P = (RT/V(m) -b) - (a/V(m) x (V(m) +b))
12. Thermodynamics
Answer:
- conversion of heat to mechanical work and vice versa
- relationship to a "large scale" bulk properties of a system that are measurable (vol,
temp...)
- describes behavior of matter and transformation between different forms of energy
on a macroscopic scale (large collections of molecules, not individual ones)
, 13. Thermochemistry
Answer:
- investigates flow of energy into or out of chemical reactions
- help deduce energy stored in chemical bonds
14. System
Answer: All the materials involved in the process under study
15. Surroundings
Answer:
- The rest of the universe
- at least those materials outside of the system with which the system interacts
16. Open system
Answer: - exchange of matter and energy
17. Closed system
Answer:
- energy exchange
- no matter exchange
18. Isolated system
Answer: - no exchange at all
19. Energy
Answer: - capacity to do work
20. Work
Answer:
- done when a force acts through a distance
- force x distance (in joules) P(atm) x (change in volume)
21. Kinetic energy
Answer: - associated with motion of a body or the particles within it
1. Newton's laws of motion
Answer:
- particles in random straight-lone motion
- separated by large distances so brief collisions
- no long range forces
- gas has internal energy only due to kinetic energy of particles
- total energy is constant
2. microscopic description of pressure
Answer: P = (1/3)(N/V) m u^2
- N = nb of particles
- m = mass of 1 particle
- u^2 = average square velocity
3. Root mean square velocity (Urms)
Answer: - close to average speed of the particles
4. Total kinetic energy
Answer: Ek = 1/2 m u^2
5. Graham's law of effusion
Answer:
- effusion - process by which a gas escapes througha tiny hole in its container into an
evacuated space
- law: rate of effusion of a gas is inversely proportional to the square root of its molar
mass
- rate of diffusion (movement of 1 gas through another) is the same way but diffusion
rates lower because gas molecule hits many other molecules (diffusion is slower)
6. Mean free path
Answer:
- average distance a molecule travels between collisions at agiven temperature and
pressure
- key factor in rate of diffusion and rate of heat flow through a gas
,7. Collision frequency
Answer:
- divide most probable speed (m/s) by the mean free path(m/collision)
- average nb of collisions per second that each particle undergoes
8. Effect of inter particle attractions
Answer:
- as p(ext) rises, volume decreases andparticles get closer so inter particle attraction
has a greater effect
- results in decreased gas pressure and so a smaller numerator in PV/RT
9. Effect of particle volume
Answer:
- at extremely high pressures, the space taken up butthe particles makes the free
volume less than the container volume
- causes numerator and so ratio to become very high in PV/RT
10. Van der waals equation
Answer:
- adjust p up by adding a factor accounting for interparticle attractions
- adjust v down bu subtracting a factor accounting for particle volume
- a and b are constants
- a depends on nb and distribution of electrons, relating to complexity of a particle
and the strength of its inter particle attraction
- b relates to the volume of the particle
11. Redlich Kwong model
Answer: P = (RT/V(m) -b) - (a/V(m) x (V(m) +b))
12. Thermodynamics
Answer:
- conversion of heat to mechanical work and vice versa
- relationship to a "large scale" bulk properties of a system that are measurable (vol,
temp...)
- describes behavior of matter and transformation between different forms of energy
on a macroscopic scale (large collections of molecules, not individual ones)
, 13. Thermochemistry
Answer:
- investigates flow of energy into or out of chemical reactions
- help deduce energy stored in chemical bonds
14. System
Answer: All the materials involved in the process under study
15. Surroundings
Answer:
- The rest of the universe
- at least those materials outside of the system with which the system interacts
16. Open system
Answer: - exchange of matter and energy
17. Closed system
Answer:
- energy exchange
- no matter exchange
18. Isolated system
Answer: - no exchange at all
19. Energy
Answer: - capacity to do work
20. Work
Answer:
- done when a force acts through a distance
- force x distance (in joules) P(atm) x (change in volume)
21. Kinetic energy
Answer: - associated with motion of a body or the particles within it
