勇之助 發問時間: 科學化學 · 1 0 年前

Physical chemistry

Initially 0.1 mol of methane is at 1bar pressure and 80℃. The gas behaves ideally and the value of Cp / Cv is 1.31. The gas is allowed to expand reversible and adiabatically to a pressure of 0.1bar.

a.What are the initial and final volumes of the gas?

b.What is the final temperature?

c.Calculate ΔU and ΔH for the process.

請詳解,越詳細越好!感恩~

1 個解答

評分
  • 1 0 年前
    最佳解答

    a.

    ∵ The gas behaves ideally

    ∴PV=nRT

    initial:

    (1bar)Vi=(0.1mol)(0.083)(80+273)

    Vi=2.93 (L)

    final:

    ∵The gas behaves ideally,expand reversible and adiabatically

    ∴PV^(Cp/Cv)=const.

    PiVi=PfVf

    1*2.93^1.31=0.1*Vf^1.31

    Vf=16.99 (L)

    b.

    ∵ The gas behaves ideally

    ∴PfVf=nRTf

    (0.1)(16.99)=(0.1)(0.083)Tf

    Tf=204.70 (K)

    c.

    by lst law

    ΔU=Q-W

    ∵adiabatically

    ∴Q=0

    W=∫PdV

    ∵The gas behaves ideally,expand reversible and adiabatically

    ∴PV^(Cp/Cv)=const.

    P=const.(V)^(-Cp/Cv)代入積分式

    W=∫(const.)V^(-1.31)dV=(const.)/(-0.31)[(Vf)^(-0.31)-Vi^(-0.31)

    =(1*10^5pa)(2.93*10^(-3) m^3)^(1.31)/(-0.31)[((2.93*10^(-3))^(-0.31)-(16.99*10^(-3))^(-0.31)]=-397.04 (J)

    ∴ΔU=Q-W=0-(-3.981)=397.04(J)

    ΔH=∫nCpdT

    or =ΔU+PΔV+VΔP

    (缺Cp數據)

    2007-03-30 14:11:39 補充:

    a.上面有打錯

    ∴PV^(Cp/Cv)=const.

    PiVi^1.31=PfVf^1.31

    參考資料: 自己
    • 登入以對解答發表意見
還有問題?馬上發問,尋求解答。