course Phy 232
Assignment 8
Ch. 19 Problems 44, 51, 56, 59, and 62
44.
Qa= Delta U +w
=150J + 450J =150J + 120
= 600 = 270J
Qb= Delta U +w
=240J + 450J
= 690J
Qc= Delta U + w
= 680J + 450J = 680J + 120J
= 1130J = 800J
Qd= Delta U + w
= 330J + 120J
= 450J
Ab:
600J- 690J= -90 (flow out of the system)
Bc:
690J – 1130J= -440 (flows out of the system)
Ad:
270J - 450J= -180 (flows out of the system)
Dc:
450J – 800J= -350 (flows out of the system)
51.
W=p(v2-v1) isobaric process
56.
1. PV=nRT
2. T2= p2/v2(nR) = 273K and nR= (p2/v2)/273K
3. T1= P1V1/ nR = p1/v1 x 273K/p2v2 = (p1/p2)x (v1/v2)x273L
4. T1= (p1/p2)(p1/p2)^-1gamma (273K)
= (p1/p2)^(1-1/1.4)x 273
= (p1/p2)^0.29 (273)
= (1.60x10^6/2.80x10^5) x173K
= (5.714)^0.29 x 273
= 452.56K
59.
A.
B.
T2=T1(V1/V2) p2=p1(V1/V2)
=27(0.250/0.166) (4.2x10^5)=(1.01x10^5)(0.250/V2)
T2= 41 degrees V2= 0.166
C. How much work does the pump do in putting 20.0mol of air into the tank?
W=n(v(t2-t1))
W= (20.0mol)(20.8)(41-27)
W= 5824
62.
A. Show the series of processes on a pv-Diagram.
I am not sure how to do this.
B. 0.25mol oxygen at 240Kpa= V=nRT/P
= 0.25mol(8.31)(355k)/(2.40x10^5pa
= 0.003m^3
Dv=2(V-V)
V= 0.0031m^2 and P= 2.4 x10^5
(0.0031)(2.4x10^5)
= 744J
C. n and T are both constant. Compress ½ the volume and it gets us double the pressure.
Max Pressure= 2 x 2.40x10^5
= 4.8x10^5Pa
D. Total Work Done
nRTln[V2]-nRTln[V1]
nRTln[V2/V1]
nRTln (1/2)
(0.25)(8.31)(710)(-7)
1000
Net Work done: 744-1000= -256J
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