One mole of an ideal monatomic gas (C_v = 3R/2) initially at 300 K is expanded f

Question

One mole of an ideal monatomic gas (C_v = 3R/2) initially at 300 K is expanded from an initial pressure of 10.0 atm to a final pressure of 1.00 atm. Calculate q, w, delta U, and delta H if the expansion is carried out by each of these paths (a) isothermal and reversible. (b) isothermal and irreversible. Explain the following phenomena according to the first law of thermodynamics. (a) When a bicycle tire is inflated with a hand pump, the temperature inside rises. You can feel the warming effect at the valve stem. (b) Artificial snow is made by quickly releasing a mixture of compressed air and water at about 20 atm from a snow making machine to the surroundings.

Explanation / Answer

Ans 3)

a) ISOTHERMAL and IRREVERSIBLE

Since tempereture is constant dT = 0 and dE = 0

dU = 0 and dH = 0 (since dT is 0)

dE = w + q = 0

w = -q

w = -Pext*dV

We know that PV =nRT

Vi = nrT/Pi = 1*8.314*300/1 = 2494.2

Vf = nRT/Pf = 8.314*300/100 = 24.942

w = -q =  -Pext*dV = 1*(24.942-2494.2) = -2469.258 J

b)Isothermal irreversible change:

dU = dH = 0 (since dT is zero)

w = -q =  nRTln (Vf/Vi)

Now PfVf = PiVi

w = -q = nRTln(Pi/Pf) = 1*300*8.314*ln(1/10)

w = -q = -5743.107 J

Related Questions

Navigate

• Browse (All)
• Browse O
• Subjects

---

---

Integrity-first tutoring: explanations and feedback only — we do not complete graded work. Learn more.