An ideal gas (1.0 mol) is the working substance in an engine that operates on the cycle shown in Figure. Processes BC and DA are reversible and adiabatic. (a) Is the gas monatomic, diatomic, or polyatomic?(b) What is the engine efficiency?

Question

broliY · Accepted Answer

a) for process D→A gives  pDVDγ=pAVAγ→p032(8V0)γ=p0V0γ  which leads to 8γ=32⇒γ=53. The result implies the gas is monatomic. b) The input heat is that absorbed during process A→B  QH=nCp△T=n(52R)TA(TBTA−1)=nRTA(52)(2−1)=p0V0(52)  and the exhaust heat is that liberated during process C→D  QL=nCp△T=n(52R)TD(1−TLTD)=nRTD(52)(1−2)=−14p0V0(52)  where in the last step we have used the fact that TD=14TA (from the gas law in ratio form). Therefore, equation 20-12 leads to  ϵ=1−|QLQH|=1−14=0.75=75%

An ideal gas (1.0 mol) is the working substance in an engine that operates on the cycle shown in Figure. Processes BC and DA are reversible and adiabatic. (a) Is the gas monatomic, diatomic, or polyatomic?(b) What is the engine efficiency?

Answered question

Answer & Explanation

New Questions in Other