Question

Calculate the final temperature?

Answer 1

When 3.50kJ of energy is transferred as heat to .75mole of IBr at 725C and 1 atm at constant pressure. IBr is an ideal gas.

Answer 2

Im not sure which formula to use. I thought about using q = nCdeltaT but I dont have the C (heat capacity) value.

Answer 3

do you know anything about the heat capacity and equipartition theorem?

Answer 4

somewhat, not enough to apply it :/

Answer 5

so... IBr is a diatomic molecule, which means that you have 3 degrees of freedom from translation, two degrees of freedom from rotation, and an extra one from vibration

Answer 6

translation and rotation counts for 1/2 R, and vibration counts for 1 R, so this whole thing has a heat capacity of 7/2 R

Answer 7

but this is not what you will be using, since this heat capacity is C_v, or for constant volume, what you need is constant pressure, so add an extra R, and you get 9/2 R

Answer 8

The reason why equipartition thm works in this case is because you're dealing with a really high temp situation, and at that point, all the modes of freedom is activated, so the heat capacity is at its max (7/2 for C_v and 9/2 for C_p)

Answer 9

heat = mC_p*delta (T), so solve for delta T, and that's your answer

Answer 10

ohh thanks so much! Makes sense now :)

Answer 11

yea, like I said. rotation and translation counts for 1/2 R each. So 3 translation = 3/2 R, and 2 rotations = 2/2 R

Then the vibration is one R each, so 1 vibration is 1R, or 2/2R.

3/2R + 2/2R + 2/2R = 7/2 R and this is the heat capacity for constant volume only.
If you want to find it at constant pressure, then add an extra R, or 2/2R, so it's 9/2R