mmmboh
Jan9-10, 03:22 PM
1. The problem statement, all variables and given/known data
Hi there, we got about 10 questions for an assignment and I have done most of them although there are a few I am unsure about.
1. Which of the following are extensive and which are intensive? The magnetic moment of gas, the electric field in a solid, the length of a wire, the surface tension of an oil film?
2. A mixture of hydrogen and oxygen is isolated and allowed to reach a state of constant temperature and pressure. The mixture is exploded with a spark of negligible energy and again allowed to come to a state of constant temperature and pressure. Is the initial state an equilibrium state? explain. Is the final state an equilibrium state? explain.
3. Describe how a system containing 2 gases can be in:
a)Mechanical but not thermal and chemical equilibrium
b)Thermal but not mechanical or chemical equilibrium
c)Thermal and mechanical equilibrium but not chemical
4. On a graph of volume versus temperature draw and label an isothermal expansion, an isothermal compression, an isochoric increase in temperature.
5. Is classical thermodynamic reasoning alone enough to determine
a) the average velocity of the molecules of a gas
b) the relation between the pressure dependence of the specific heat capacity of a solid and the temperature dependence of its volume.
c) the magnitude of the magnetic moment of a gas
d) the relation between the pressure and temperature of electromagnetic radiation in a cavity.
e) The magnitude of the specific heat capacity of a solid.
Briefly justify your answers.
3. The attempt at a solution
1. For the magnetic moment of a gas, I put extensive, for the electric field in a solid I put intensive, for the length of a wire I put intensive, and for the surface tension of an oil film I put extensive. Is this all correct?
2. Ok for this question I reasoned that a state of constant temperature and pressure means it is in thermal and mechanical equilibrium, satisfying two out of the three conditions. So in the initial state I thought it wasn't in chemical equilibrium because the hydrogen and oxygen atoms would be reacting but very slowly because they don't have enough energy to convert to water. (I'm not sure if that means they aren't in chemical equilibrium though, maybe that just means they aren't reacting at all and so are in equilibrium?). For the final state I reasoned that it was in equilibrium because it was in thermal and mechanical equilibrium, as well as chemical because the spark allowed the hydrogen and oxygen to convert to water.
Is this correct? I'm not even sure if it does convert to water because it says the spark has negligible energy, was if it wasn't negligible then would it not be in equilibrium? maybe the question has nothing to do with water and I am completely wrong I am not even sure.
3a) A system containing two gases can be in mechanical but not thermal or chemical equilibrium if the gases aren't moving, however the temperature at every point in the system isn't equal and the gases are not finished reacting with each other.
b) A system can be in thermal but not mech. of chem. equilibrium if the temperature at every point in the system is the same however the gases are moving and the are not finished reacting with each other.
c) A system can be in thermal and mech. equilibrium but not in chem. if the temperature is the same everywhere and the gases are not moving but they are still reacting.
4. For the isothermal expansion I drew temperature on the y-axis and volume on the x-axis, and drew a line of constant temperature in the increasing x-direction.
For the isothermal compression I drew the same thing as the isothermal expansion except I drew the line in the decreasing x direction starting from 0.
For the isochoric increase in temperature I drew the volume on the y-axis and the temperature on the x-axis and drew a line of constant volume in the increasing x-direction.
Is this right?
5. Ok for a) I am just not sure, does it have something to do with PV=nRT, and that pressure is F/A and that F is change in momentum over change in time? and so the answer would be yes? For b) Does this also have to do with PV=nRT? c)I would say no, I don't know what magnetism has to do with thermodynamics, help? d) I'm really not sure about this one, I would guess yes. e) I know C=Q/(mt)...so I would say yes, but I am not sure how to explain it.
Thanks for any help :)
Hi there, we got about 10 questions for an assignment and I have done most of them although there are a few I am unsure about.
1. Which of the following are extensive and which are intensive? The magnetic moment of gas, the electric field in a solid, the length of a wire, the surface tension of an oil film?
2. A mixture of hydrogen and oxygen is isolated and allowed to reach a state of constant temperature and pressure. The mixture is exploded with a spark of negligible energy and again allowed to come to a state of constant temperature and pressure. Is the initial state an equilibrium state? explain. Is the final state an equilibrium state? explain.
3. Describe how a system containing 2 gases can be in:
a)Mechanical but not thermal and chemical equilibrium
b)Thermal but not mechanical or chemical equilibrium
c)Thermal and mechanical equilibrium but not chemical
4. On a graph of volume versus temperature draw and label an isothermal expansion, an isothermal compression, an isochoric increase in temperature.
5. Is classical thermodynamic reasoning alone enough to determine
a) the average velocity of the molecules of a gas
b) the relation between the pressure dependence of the specific heat capacity of a solid and the temperature dependence of its volume.
c) the magnitude of the magnetic moment of a gas
d) the relation between the pressure and temperature of electromagnetic radiation in a cavity.
e) The magnitude of the specific heat capacity of a solid.
Briefly justify your answers.
3. The attempt at a solution
1. For the magnetic moment of a gas, I put extensive, for the electric field in a solid I put intensive, for the length of a wire I put intensive, and for the surface tension of an oil film I put extensive. Is this all correct?
2. Ok for this question I reasoned that a state of constant temperature and pressure means it is in thermal and mechanical equilibrium, satisfying two out of the three conditions. So in the initial state I thought it wasn't in chemical equilibrium because the hydrogen and oxygen atoms would be reacting but very slowly because they don't have enough energy to convert to water. (I'm not sure if that means they aren't in chemical equilibrium though, maybe that just means they aren't reacting at all and so are in equilibrium?). For the final state I reasoned that it was in equilibrium because it was in thermal and mechanical equilibrium, as well as chemical because the spark allowed the hydrogen and oxygen to convert to water.
Is this correct? I'm not even sure if it does convert to water because it says the spark has negligible energy, was if it wasn't negligible then would it not be in equilibrium? maybe the question has nothing to do with water and I am completely wrong I am not even sure.
3a) A system containing two gases can be in mechanical but not thermal or chemical equilibrium if the gases aren't moving, however the temperature at every point in the system isn't equal and the gases are not finished reacting with each other.
b) A system can be in thermal but not mech. of chem. equilibrium if the temperature at every point in the system is the same however the gases are moving and the are not finished reacting with each other.
c) A system can be in thermal and mech. equilibrium but not in chem. if the temperature is the same everywhere and the gases are not moving but they are still reacting.
4. For the isothermal expansion I drew temperature on the y-axis and volume on the x-axis, and drew a line of constant temperature in the increasing x-direction.
For the isothermal compression I drew the same thing as the isothermal expansion except I drew the line in the decreasing x direction starting from 0.
For the isochoric increase in temperature I drew the volume on the y-axis and the temperature on the x-axis and drew a line of constant volume in the increasing x-direction.
Is this right?
5. Ok for a) I am just not sure, does it have something to do with PV=nRT, and that pressure is F/A and that F is change in momentum over change in time? and so the answer would be yes? For b) Does this also have to do with PV=nRT? c)I would say no, I don't know what magnetism has to do with thermodynamics, help? d) I'm really not sure about this one, I would guess yes. e) I know C=Q/(mt)...so I would say yes, but I am not sure how to explain it.
Thanks for any help :)