{[ promptMessage ]}

Bookmark it

{[ promptMessage ]}

ProbSet7Solutions

# ProbSet7Solutions - Solutions to Problem Set 7 6.4(a The...

This preview shows pages 1–2. Sign up to view the full content.

Solutions to Problem Set 7 6.4 (a) The work done is given by : (4 cylinders).(60 cycles/min).(-1400 bar. 10 5 Pa/bar). (2.5 L. 0.001m 3 /L) = -8.4 x 10 7 J (b) The expanding gas in the cylinder does work on the pistons. Therefore, the work done by the gas is negative. 6.8. To calculate this, we can use the relationship Ä U = q + w, which arises from the first law of thermodynamics. Because the system releases heat, q will be a negative number as will Ä U, because it is a decrease in internal energy: -125 kJ = -346 kJ + w w = 221 kJ. Because work is positive, surrounding will do work on the system. 6.16 (a) The heat change will be made of two terms: one term to raise the temperature of the stainless steel and the other to raise the temperature of the water: q = 450.0 x 4.18 x (100 – 25) + 500.0 x 0.51 x (100 -25) = 141 kJ + 19 kJ = 160 kJ (b) The percentage of heat attributable to the raising of the temperature of the water will be (141/160)x100 = 88.1% (c) The use of copper kettle is more efficient as a larger percentage of the heat goes into heating the water and not the container holding it. 6.22 (a) Because the process is isothermal, Ä U = 0 and q = -w. For a reversible process, w = -nRT ln(V2/V1) n is obtained from the ideal gas equation: n = PV/RT = 0.359 mol w = -(0.359)(8.314)(298)ln(7.39/3.42) = -685 J q = +685 J (b) For step 1, because volume is constant, w = 0 , Ä U = q In step 2, there is an irreversible expansion against constant pressure, W = -P(V final - V initial )= - 1.19 atm (7.39 L – 3.42 L) = -4.72 L.atm = (-4.72 L.atm)(101.325 J/1 L.atm) = -479 J.

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

View Full Document
This is the end of the preview. Sign up to access the rest of the document.

{[ snackBarMessage ]}

### Page1 / 4

ProbSet7Solutions - Solutions to Problem Set 7 6.4(a The...

This preview shows document pages 1 - 2. Sign up to view the full document.

View Full Document
Ask a homework question - tutors are online