FES EXAM QUESTIONS AND VERIFIED DETAILED ANSWERS |ALREADY GRADED
A+| 2024/2025 UPDATE
15 kg/s of air are compressed from 1 atm and 300K (enthalpy of 300.19 kJ/kg) to 2 atm and 900K
(enthalpy of 732.93 kJ/kg). Heat transfer is negligible. The air compressor's power output is most nearly
(A) 5.6 MW
(B) 6.5 MW
(C) 7.6 MW
(D) 8.9 MW - ✔ANSWER B
What is most nearly the weight in lbf if a 1.00lbm object in a gravitational field of 27.5ft/s^2?
(A) 0.85lbf
(B) 1.2lbf
(C) 28lbf
(D) 32lbf - ✔ANSWER A
What is the ideal efficiency of an air-standard Otto cycle with a compression ratio of 6:1?
(A) 17%
(B) 19%
(C) 49%
(D) 51% - ✔ANSWER D
An electric motor is tested in a brake that uses a Kevlar belt to apply frictional resistance to a 22 cm
radius hub. The tight side tension is measured by a spring scale A as 30 N. The slack side tension is
measured by spring scale B as 10 N. The motor turns at 1725 rpm. Most nearly, what is the motor
horsepower?
(A) 0.17 hp
(B) 0.50 hp
,(C) 0.80 hp
(D) 1.1 hp - ✔ANSWER D
A refrigeration cycle has a coefficient of performance of 2.2. The cycle exchanges heat between two
infinite thermal reservoirs. For each 6 kW of cooling, what is most nearly the power input required?
(A) 1.4 kW
(B) 2.7 kW
(C) 5.5 kW
(D) 8..1 kW - ✔ANSWER B
A heat pump takes heat from groundwater at 7*C and maintains a room at 21*C. What is most nearly
the maximum coefficient of performance possible for this heat pump?
(A) 1.4
(B) 2.8
(C) 5.6
(D) 21 - ✔ANSWER D
A 2L container holds a mixture of three inert gases. The pressure inside the container is measured at 1.5
atm at a temperature of 293K (room temperature). Two of the three inert gases are known. The first gas,
krypton, has a mass fraction of 0.352. The second gas, argon, has a mass fraction of 0.2799. The
combined mass of argon and krypton in the container is 5.630 g. What is most nearly the mass of the
third gas?
(A) 2.5 g
(B) 3.1 g
(C) 3.3 g
(D) 5.6 g - ✔ANSWER C
,A 10 mole mixture of three gases is stored in a container. There are 2 moles of helium and 3 moles of
nitrogen in the mixture. What is most nearly the mole fraction of the third gas in the mixture?
(A) 0.20
(B) 0.30
(C) 0.50
(D) 0.75 - ✔ANSWER C
A gas mixture consisting of 4 moles of N2, 2.5 moles of CO2, and unknown amount of CO is held at two
times atmospheric pressure in a container with a volume of 0.13 m^3. The total moles in the mixture is
8.5. The total temperature of the mixture is 100*C. What is most nearly the mass fraction of Co in the
mixture?
(A) 0.10
(B) 0.20
(C) 0.48
(D) 0.53 - ✔ANSWER B
1g of oxygen and 2 g of helium are mixed in a gas sampling bag. The gases are at 50*C and atmospheric
pressure. What is most nearly the volume of the bag?
(A) 0.002 m^3
(B) 0.007 m^3
(C) 0.012 m^3
(D) 0.014 m^3 - ✔ANSWER D
A mixture contains 50 g of nitrogen and 25 g of carbon dioxide. The gases are stored in a container at
500K. At this temperature, the molar enthaply of the nitrogen is 5912 J/mol, and the molar enthaply of
the carbon dioxide is 8314 J/mol. What is most nearly the total enthalpy of the mixture?
(A) 5.7 kJ
, (B) 8.3 kJ
(C) 11 kJ
(D) 15 kJ - ✔ANSWER D
A nonvolatile, non-electrolytic liquid is combined with a solid to form a solution that just boils at 1 atm
pressure. The vapor pressure of the pure liquid is 850 torr. Most nearly, what is the molar percentage of
the liquid in the solution?
(A) 64%
(B) 79%
(C) 86%
(D) 89% - ✔ANSWER D
A rocket that has a mass of 4000 lbm travels at 27,000 ft/sec. What is most nearly its kinetic energy?
(A) 1.4 x 10^9 ft-lbf
(B) 4.5 x 10^10 ft-lbf
(C) 1.5 x 10^12 ft-lbf
(D) 4.7 x 10^13 ft-lbf - ✔ANSWER B
A 10kg block hangs from a cable. What is most nearly the tension in the cable?
(A) 1.0N
(B) 9.8N
(C) 65N
(D) 98N - ✔ANSWER D
A 10 kg block is raised vertically 3 m. What us most nearly the change in potential energy?
(A) 30 J
(B) 98 J
A+| 2024/2025 UPDATE
15 kg/s of air are compressed from 1 atm and 300K (enthalpy of 300.19 kJ/kg) to 2 atm and 900K
(enthalpy of 732.93 kJ/kg). Heat transfer is negligible. The air compressor's power output is most nearly
(A) 5.6 MW
(B) 6.5 MW
(C) 7.6 MW
(D) 8.9 MW - ✔ANSWER B
What is most nearly the weight in lbf if a 1.00lbm object in a gravitational field of 27.5ft/s^2?
(A) 0.85lbf
(B) 1.2lbf
(C) 28lbf
(D) 32lbf - ✔ANSWER A
What is the ideal efficiency of an air-standard Otto cycle with a compression ratio of 6:1?
(A) 17%
(B) 19%
(C) 49%
(D) 51% - ✔ANSWER D
An electric motor is tested in a brake that uses a Kevlar belt to apply frictional resistance to a 22 cm
radius hub. The tight side tension is measured by a spring scale A as 30 N. The slack side tension is
measured by spring scale B as 10 N. The motor turns at 1725 rpm. Most nearly, what is the motor
horsepower?
(A) 0.17 hp
(B) 0.50 hp
,(C) 0.80 hp
(D) 1.1 hp - ✔ANSWER D
A refrigeration cycle has a coefficient of performance of 2.2. The cycle exchanges heat between two
infinite thermal reservoirs. For each 6 kW of cooling, what is most nearly the power input required?
(A) 1.4 kW
(B) 2.7 kW
(C) 5.5 kW
(D) 8..1 kW - ✔ANSWER B
A heat pump takes heat from groundwater at 7*C and maintains a room at 21*C. What is most nearly
the maximum coefficient of performance possible for this heat pump?
(A) 1.4
(B) 2.8
(C) 5.6
(D) 21 - ✔ANSWER D
A 2L container holds a mixture of three inert gases. The pressure inside the container is measured at 1.5
atm at a temperature of 293K (room temperature). Two of the three inert gases are known. The first gas,
krypton, has a mass fraction of 0.352. The second gas, argon, has a mass fraction of 0.2799. The
combined mass of argon and krypton in the container is 5.630 g. What is most nearly the mass of the
third gas?
(A) 2.5 g
(B) 3.1 g
(C) 3.3 g
(D) 5.6 g - ✔ANSWER C
,A 10 mole mixture of three gases is stored in a container. There are 2 moles of helium and 3 moles of
nitrogen in the mixture. What is most nearly the mole fraction of the third gas in the mixture?
(A) 0.20
(B) 0.30
(C) 0.50
(D) 0.75 - ✔ANSWER C
A gas mixture consisting of 4 moles of N2, 2.5 moles of CO2, and unknown amount of CO is held at two
times atmospheric pressure in a container with a volume of 0.13 m^3. The total moles in the mixture is
8.5. The total temperature of the mixture is 100*C. What is most nearly the mass fraction of Co in the
mixture?
(A) 0.10
(B) 0.20
(C) 0.48
(D) 0.53 - ✔ANSWER B
1g of oxygen and 2 g of helium are mixed in a gas sampling bag. The gases are at 50*C and atmospheric
pressure. What is most nearly the volume of the bag?
(A) 0.002 m^3
(B) 0.007 m^3
(C) 0.012 m^3
(D) 0.014 m^3 - ✔ANSWER D
A mixture contains 50 g of nitrogen and 25 g of carbon dioxide. The gases are stored in a container at
500K. At this temperature, the molar enthaply of the nitrogen is 5912 J/mol, and the molar enthaply of
the carbon dioxide is 8314 J/mol. What is most nearly the total enthalpy of the mixture?
(A) 5.7 kJ
, (B) 8.3 kJ
(C) 11 kJ
(D) 15 kJ - ✔ANSWER D
A nonvolatile, non-electrolytic liquid is combined with a solid to form a solution that just boils at 1 atm
pressure. The vapor pressure of the pure liquid is 850 torr. Most nearly, what is the molar percentage of
the liquid in the solution?
(A) 64%
(B) 79%
(C) 86%
(D) 89% - ✔ANSWER D
A rocket that has a mass of 4000 lbm travels at 27,000 ft/sec. What is most nearly its kinetic energy?
(A) 1.4 x 10^9 ft-lbf
(B) 4.5 x 10^10 ft-lbf
(C) 1.5 x 10^12 ft-lbf
(D) 4.7 x 10^13 ft-lbf - ✔ANSWER B
A 10kg block hangs from a cable. What is most nearly the tension in the cable?
(A) 1.0N
(B) 9.8N
(C) 65N
(D) 98N - ✔ANSWER D
A 10 kg block is raised vertically 3 m. What us most nearly the change in potential energy?
(A) 30 J
(B) 98 J
