Thermal Physics: Please answer Part A and B only, C and D is asked in another ch

Question

Thermal Physics:

Please answer Part A and B only, C and D is asked in another chegg study question.

This is an example of how to use the first law and the area representation of work in the pV-diagram. The figure below shows several possible processes leading through the (p, V) diagram of an unspecified substance. Do not presume the substance is a dilute gas. Along path I rightarrow a f it is found that the object receives Q = 50 J in heat and that it does W = 20 J in work; along path i rightarrow b rightarrow f it is found that Q = 36 J. What is W along path I rightarrow b rightarrow? If W = -13 J along the curved path f rightarrow I, what is Q for this path? If the internal energy is equal to U = 10 J at point i, what is its value at point f ? If the internal energy is equal to U = 10 J at point i and U = 22 J at point b, what is Q for process i rightarrow b and for process b rightarrow f ?

Explanation / Answer

From first law of thrmodynamics,        dQ = dU + dW

dQ = heat,      dU = change in internal energy,    dW = work done

For curve i-a-f:

Qiaf = Wiaf + dUfi

50 = 20 + dUfi

dUfi = 50-20 = 30 J                      -------------------------1

(A) for curve i-b-f:

Qibf = Wibf + dUfi

36 = Wibf + 30                               ( by putting the value of dUfi from eq. 1)

Wibf = 36-30 = 6 J

(B) for curve f-i:

Qfi = Wfi +dUfi

    = - 13 + 30

    = 17 J

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