Tiêu đề 12.THERMODYNAMICS - Questions.pdf ✅

12.THERMODYNAMICS (1.)A Carnot engine has efficiency 1/5. Efficiency becomes 1/3 when temperature of sink is decreased by 50K. What is the temperature of sink? (a.) 325 K (b.) 375 K (c.) 300 K (d.) 350 K (2.)A refrigerator absorbs 2000 cals of heat from ice trays. If the coefficient of performance is 4, then work done by the motor is (a.) 2100 J (b.) 4200 J (c.) 8400 J (d.) 500 J (3.)When the amount of work done is 333 cal and change in internal energy is 167 cal, then the heat supplied is (a.) 166 cal (b.) 333 cal (c.) 500 cal (d.) 400 cal (4.)Carnot cycle (reversible) of a gas represented by a Pressure-Volume curve is shown in the diagram Consider the following statements I. Area ABCD = Work done on the gas II. Area ABCD = Net heat absorbed III. Change in the internal energy in cycle = 0 Which of these are correct (a.) I only (b.) II only (c.) II and III (d.) I, II and III (5.)An ideal gas is heated at constant pressure and absorbs amount of heat Q. If the adiabatic exponent is γ, then the fraction of heat absorbed in raising the internal energy and performing the work, in (a.) 1 − 1 γ (b.) 1 + 1 γ (c.) 1 − 2 γ (d.) 1 + 2 γ (6.)For an adiabatic expansion of a perfect gas, the value of ∆P P is equal to (a.) −√γ ∆V V (b.) − ∆V V (c.) −γ ∆V V (d.) −γ 2 ∆V V (7.)In the following p − V diagram figure two adiabates cut two isothermals at T1 and T2. The value of Vb/Vc is (a.) = Va/Vd (b.) < Va/Vd (c.) > Va/Vd (d.) Cannot say (8.)A gas expands 0.25m3 at constant pressure 103N/m2 , the work done is (a.) 2.5 ergs (b.) 250 J (c.) 250 W (d.) 250 N (9.)Ten moles of an ideal gas at constant temperature 500 K is compressed from 50 L to 5 L. Work done in the process is (Given, R = 8.31 J − mol −1 − K −1 ) (a.) −1.2 × 104 J (b.) −2.4 × 104 J (c.) −4.8 × 104 J (d.) −9.6 × 104 J (10.)If an ideal gas is compressed isothermally then (a.) No work is done against gas (b.) Heat is released by the gas (c.) The internal energy of gas will increase (d.) Pressure does not change (11.)The work done, W during an isothermal process in which 1 mole of the gas expands from an initial volume V1 to a final volume V2 is given by (R=gas constant, T=temperature) (a.) R(V2 − V1 ) loge ( T1 T2 ) (b.) R(T2 − T1 ) loge ( V2 V1 ) (c.) RT loge( V2 V1 ) (d.) 2RT loge ( V1 V2 ) (12.)Two isothermally are shown in figure at temperature T1 and T2. Which of the following relations is correct? A D C B P V


bucket of water at 50°C (Assume temperature of water does not change) (a.) −4.5 cal/K (b.) +4.5 cal/K (c.) +5.4 cal/K (d.) −5.4 cal/K (38.)The sink temperature of a heat engine 77°C. The efficiency is 30%. The source temperature is (a.) 500°C (b.) 227°C (c.) 317°C (d.) 427°C (39.)Figure shows a thermodynamical process on one moles a gas. How does the work done in the process change with time? (a.) Decrease continuously (b.) Increases continuously (c.) Remains constant (d.) First increase and then decreases (40.)When 1 kg of ice at 0°C melts to water at 0°C, the resulting change in its entropy, taking latent heat of ice to be 80 cal/°C is (a.) 293 cal/K (b.) 273 cal/K (c.) 8 × 104 cal/K (d.) 80 cal/K (41.)A container having 1 mole of a gas at a temperature 27°C has a movable piston which maintains at constant pressure in container of 1 atm. The gas is compressed until temperature becomes 127°C. The work done is (Cpfor gas is 7.03cal/mol − K) (a.) 703 J (b.) 814 J (c.) 121 J (d.) 2035 J (42.)The temperature of a hypothetical gas increases to √2 times when compressed adiabatically to half the volume. Its equation can be written as (a.) PV 3/2 = constant (b.) PV 5/2 = constant (c.) PV 7/3 = constant (d.) PV 4/3 = constant (43.)Three samples of the same gas A, B and C(γ = 3/2) have initially equal volume. Now the volume of each sample is doubled. The process is adiabatic for A isobaric for B and isothermal for C. If the final pressure are equal for all three samples, the ratio of their initial pressures are (a.) 2√2 ∶ 2 ∶ 1 (b.) 2√2 ∶ 1 ∶ 2 (c.) √2 ∶ 1 ∶ 2 (d.) 2 ∶ 1 ∶ √2 (44.)In the cyclic process shown in the figure, the work done by the gas in one cycle is (a.) 28 P1V1 (b.) 14 P1V1 (c.) 18 P1V1 (d.) 9 P1V1 (45.)The change in internal energy, when a gas is cooled from 927°C to 27°C (a.) 300% (b.) 400% (c.) 200% (d.) 100% (46.)dU+dW=0 is valid for (a.) Adiabatic process (b.) Isothermal process (c.) Isobaric process (d.) Isochoric process (47.)An ideal heat engine works between temperatures T1 = 500K and T2 = 375K. If the engine absorbs 600 J of heat from the source, then the amount of heat released to the sink is (a.) 450 J (b.) 600 J (c.) 45 J (d.) 500 J (48.)If heat given to a system is 6 kcal and work done is 6 kJ. Then change in internal energy is (a.) 19.1 kJ (b.) 12.5 kJ (c.) 25 kJ (d.) Zero (49.)The pressure and density of a given mass of a diatomic gas (γ = 7 5 ) change adiabatically from (p, d) to (p’, d’). If d′ d = 32, then P′ p is (γ = ratio of specific heats) (a.) 1/128 (b.) 1/64 (c.) 64 (d.) 128 V1 4V1 P1 7P1 P V