Ch14_1
 
New Problems reloads the page with new variable values in all questions. You must do this after grading the test to rework it another time.
Make sure to calculate your answers in SI units unless specified otherwise .
1) A gas expands at a constant pressure of atm its volume from liter to liter. What is the work done by the gas (see sheet 7; include the correct sign) ?
2) cal heat are added to a gas which does J work by expanding. What is the change in internal energy of the gas (see sheet 8) ? Indicate with a positive (negative) sign whether the internal energy increases (decreases).
3) moles of a gas at room temperature (20 oC) expand quickly ("adiabatically") at an average pressure of atm increasing its volume by cm3. What is the final temperature in oC (see sheet 7,8,11') ? (NOTE! The change in volume given, not the volume itself. Thus you cannot use the gas equation to get the number of molecules.) Indicate with a positive (negative) sign whether the temperature decreases (increases).
4) The internal energy of a gas is quickly ("adiabatically") increased by J at an average pressure of atm. What is the change in volume (see sheet 7,8) ? Indicate with a negative (positive) sign whether the gas is compressed (expands).
5) A gas does J of work at constant temperature ("isothermal"). How much heat is exchanged with the environment (see sheet 8,12') ? Indicate with a positive (negative) sign whether heat is put into (taken out of) the gas.

6) An ideal gas changes its pressure and volume as shown in the PV-diagram starting at point A and returning to it. The pressure PAB is atm and volume VB is cm3. How many calories are exchanged with the environment if J of work is done on the gas during the trip B-C (see sheet 7,8) ? (Hint: The heat exchange Q asked for is for the complete "trip" A to B to C to A. What does the gas equation tell you about the temperature change, and hence about the change in internal energy, for the complete trip, when the gas returns to the same PV-pair in point A (see sheet 3,5)) ? When calculating the work you must split the complete trip into 3 pieces, WAB+ WBC+WCA.) Indicate with a positive (negative) sign whether heat is put into (taken out of) the gas.


Once you have submitted your answers for grading by clicking the grade button, you cannot resubmit answers for the same Problem Set--you must use the 'New Problems' button first.