QUESTION 1: An ideal gas initially at 340 K undergoes an isobaric expansion at 2
ID: 2298502 • Letter: Q
Question
QUESTION 1: An ideal gas initially at 340 K undergoes an isobaric expansion at 2.50 kPa. The volume increases from 1.00 m3 to 3.00 m3 and 14.6 kJ is transferred to the gas by heat.
(a) What is the change in internal energy of the gas?______kJ
(b) What is the final temperature of the gas?_____K
QUESTION 2: In the figure below, the change in internal energy of a gas that is taken from A to C along the blue path is +775 J. The work done on the gas along the red path ABC is -430 J.
(a) How much energy must be added to the system by heat as it goes from A through B to C?
J
(b) If the pressure at point A is five times that of point C, what is the work done on the system in going from C to D?
J
(c) What is the energy exchanged with the surroundings by heat as the gas goes from C to A along the green path?
J
(d) If the change in internal energy in going from point D to point A is +495 J, how much energy must be added to the system by heat as it goes from point C to point D?
J
Explanation / Answer
Work done by gas = - P ?V ;
W = - 2.5e3 ( 3 -1 ) J ;
Q = + 13.2e3 J ;
a .
?U = -2.5*2e3 + 13.2e3 ;
change in U = 8.2 kJ ;
b .
PV = nRT ;
2.5e3 * 1 = n * 8.314 * 345 ;
n= 0.8715 = m / M ; or m = 29*0.8715 = 0.025276 kg
?U = mCp ?T ;
?T = 8.2e3 / ( 0.025276 * 1.005e3 ) = 322.804 K
final temperature= 322.804 +345 = 667.804 K <--ans