Thermodynamics
Thermodynamics
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See all →- One mole of an ideal gas expands isothermally at 300 K to twice its initial volume. The work done by the gas is approximately (R = 8.314 J mol-1 K-1, ln 2 = 0.693) Answer: B. 1729 J W=nRTlnV₂/V₁=8.314×300×0.693≈1729 J. 1
- A Carnot engine has efficiency 40% with its sink at 300 K. Keeping the sink temperature constant, by how much should the source temperature be increased to raise the efficiency to 50%? Answer: C. 100 K 0.4=1-300/T₁⇒ T₁=500 K. For 50%: T₁'=600 K. Increase =100 K. 1
- A hypothetical thermodynamic cycle is shown in the figure. Calculate the work done in 25 cycles. Given : a = fracΔV_max2=6-2/2×10⁻³m³ = 2 x 10⁻³ m³, b = fracΔP_max2=11-1/2×10⁵Pa = 5 x 10^(5 )Pa Cycles = 25 The work done in one cycle, oin... 1
- An ideal monatomic gas is adiabatically compressed so that its final temperature is twice its initial temperature. Given : T_f = 2T_i, monatomic gas ϒ = 5/3 P_iV_i^ϒ = P_fV_f^ϒ in an adiabatic process Now, PV= nRT ∴ V = nRT/P ∴ V_(i )= nRT_i/P_i and V_(f... 1
- An ideal gas is taken through an isothermal process. If it does 2000 J of work on its environment Given : W = 2000J , isothermal process In this case, the change in the internal energy of the gas, ΔU=0, as the gas is taken through an isot... 1
- A Carnot refrigerator operates between 250ºK and 300ºK. Calculate its coefficient of performance. Given : T_C = 250 K, T_H = 300 K K = T_C/T_H-T_C=250/300-250=250/50 = 5 this is the coefficient of performance of the refrigerator. 1