HW2 Assn - Christie Donahue 92337669 Homework#2 1 1.11 A...

Info iconThis preview shows pages 1–3. Sign up to view the full content.

View Full Document Right Arrow Icon
Christie Donahue 92337669 Homework #2 September 26, 2007 1) 1.11 A sample of methane of mass 4.5 g (4.5g(1mol/16.04g)=.2804mol) occupies 12.7 L at 310K. a) Calculate work done when the gas expands isothermally (delta T=0) against a constant external pressure of 30.0kPa until its volume is increased by 3.3 L. J v v p W v v p W pdv dw f ex f v v f 99 ) 3 . 3 ( 30 ) ( ) ( 0 0 0 - = - = - - = - = = b) Calculate the work that would be done if the same expansion occurred isothermally and reversibly. J L L K mol v v nRT W molK J i f 9 . 166 7 . 12 16 ln * 310 * 31451 . 8 * 2804 . ln - = - = - = 2) 1.16 A lab animal exercised on a treadmill, which, through pulleys, raised a mass of 200g (.2kg) through 1.55m. At the same time, the animal lost 5.0J of energy as heat (q=-5J). Disregarding all other losses and regarding the animal as a closed system, what is the change in internal energy of the animal? J m kg d F w w q U s m 038 . 3 55 . 1 * 8 . 9 * 2 . * 2 = = = + = The work is negative since the system (the rat) does work on the surroundings. w= -3.038 J J J J U 038 . 8 038 . 3 5 - = - - =
Background image of page 1

Info iconThis preview has intentionally blurred sections. Sign up to view the full version.

View Full Document Right Arrow Icon
3) 1.17 The internal energy of a perfect gas does not change when the gas undergoes isothermal expansion (by definition). What is the change in enthalpy? 0 0 0 = = = + = + = m m m m m m H U and T T R U H RT U H In isothermal expansion, delta T=0. Therefore, there is no change in internal energy. 4) 1.18 A sample of serum of mass 25g (.025kg) is cooled from 290K to 275K (deltaT=-15K) at a constant pressure (deltaP=0) by the extraction of 1.2kJ of energy as heat. Calculate q and deltaH and estimate the heat capacity of the sample. q= 1200J The heat is a positive value because the heat is being forcefully extracted as work from the system. Since there is no change in volume, no work is done on or by the serum.
Background image of page 2
Image of page 3
This is the end of the preview. Sign up to access the rest of the document.

{[ snackBarMessage ]}

Page1 / 5

HW2 Assn - Christie Donahue 92337669 Homework#2 1 1.11 A...

This preview shows document pages 1 - 3. Sign up to view the full document.

View Full Document Right Arrow Icon
Ask a homework question - tutors are online