Exam 15: Thermodynamics

An refrigerator keeps food in the freezer portion at -15 $^{\circ}$ C and dumps excess heat into the kitchen,whose temperature is 22 $^{\circ}$ C.If the refrigerator has half the coefficient of performance of an ideal reversible refrigerator,and if its motor can supply 250W of power,what is the rate of heat flow out of the freezer portion of the refrigerator?

An engineer uses a river (minimum temperature of 4 $^{\circ}$ C)to cool his electrical plant which heats water with a boiler operating at 220 $^{\circ}$ C.His boiler uses 420 kW of energy to heat water to steam.What is the maximum power output under ideal circumstances?

If 30 kJ of heat flows into a system and the internal energy increases by 15 kJ,then what is the work done by or on the system?

If 30 kJ of heat flows out of a system and 15 kJ of work is done by the system,then what is the change in internal energy?

A monatomic ideal gas at 27 $^{\circ}$ C undergoes an isobaric process from A to B followed by an isochoric process from B to C.What is the total work done in these two processes? (A = 2atm,1L; B = 2atm,2L; C = 1atm,2L)

Using 0.0200 mol of an ideal monatomic gas,an isochoric process from A (230 kPa,1.00 L)to B (98 kPa,1.00 L)results in what change in internal energy?

It can be shown that the change in entropy in heating or cooling a sample is given by the relation $\Delta$ S = mc ln (T_F/T_i),where m is the mass of the sample,c is the specific heat of the sample,and T_F and T_i are the final and initial temperatures respectively.What is the change in entropy when 10.0 grams of lead with a specific heat of 0.452 J/gm K is heated from 10.0 $^{\circ}$ C to 50.0 $^{\circ}$ C?

An ideal gas is in contact with a heat reservoir to that it remains at a constant temperature of 300.0 K.The gas is compressed from 24.0 L to 14.0 L.The mechanical device that operating the piston to compress the gas expends 5.00 kJ of energy.How much heat flows between the gas and the heat reservoir?

An refrigerator keeps food in the freezer portion at -15 $^{\circ}$ C and dumps excess heat into the kitchen,whose temperature is 20 $^{\circ}$ C.If the refrigerator has half the coefficient of performance of an ideal reversible refrigerator,what is the refrigerator's coefficient of performance under these conditions?

In an isochoric process,the internal energy of a system decreases by 50J.What is the heat exchange?

It can be shown that the change in entropy in heating or cooling a sample is given by the relation $\Delta$ S = mc ln (T_F/T_i),where m is the mass of the sample,c is the specific heat of the sample,and T_F and T_i are the final and initial temperatures respectively.What is the change in entropy when 20 grams of aluminum with a specific heat of 0.900 J/gm K is cooled from 60.0 $^{\circ}$ C to 10.0 $^{\circ}$ C?

An engine delivers 40.0 J of work while it takes in energy from a 400 K thermal source.If the engine discharges energy into a thermal reservoir at 200 K,then what is the least amount of heat needed to run the engine?

In an isochoric process,the internal energy of a system decreases by 50J.What is the work done?

When 2.000 kg of water evaporates,22.60 $\times$ 10⁵ J/kg of heat are needed.What is the entropy change in the boiling process?

When the first law of thermodynamics is applied to an ideal gas that is taken through an isothermal process

For a system undergoing an isothermal expansion,the work done on the working fluid is:

On a PV diagram representing an isothermal compression,what is the relationship between the initial P value and the final P value?

On a PV diagram where pressure is in atmospheres and V is in liters the area is measured in liter-atmospheres.What is the number of Joules in 1.00 liter-atmosphere?

A toy steam engine has a mass of 1.00 kg.The toy starts from rest and reaches a velocity of 4.00 m/s in a time of 3.00 seconds while covering a distance of 4.50 meters.During that time the toy takes in 30 J of heat.What is the change in the internal energy of the toy?

A heat pump takes in energy from a 250 K thermal reservoir outside a house and discharges 140 J of energy into a 350 K thermal reservoir inside a house.What is the minimum amount of work needed to make the pump work?