# GATE Questions & Answers of Properties of Pure Substances

## What is the Weightage of Properties of Pure Substances in GATE Exam?

Total 11 Questions have been asked from Properties of Pure Substances topic of Thermodynamics subject in previous GATE papers. Average marks 1.73.

The volume and temperature of air (assumed to be an ideal gas) in a closed vessel is 2.87 m3 and 300 K, respectively. The gauge pressure indicate by a manometer fitted to the wall of the vessel is 0.5 bar. If the gas constant of air is = 287 J/kg·K and the atmospheric pressure is 1 bar, the mass of air (in kg) in the vessel is

The INCORRECT statement about the characteristics of critical point of a pure substance is that

1.5 kg of water is in saturated liquid state at 2 bar (vf = 0.001061 m3/kg, uf = 504.0 kJ/kg, hf = 505 kJ/kg). Heat is added in a constant pressure process till the temperature of water reaches 400°C (v = 1.5493 m3/kg, u = 2967.0 kJ/kg, h = 3277.0 kJ/kg). The heat added (in kJ) in the process is _______

A pure substance at 8 MPa and 400 °C is having a specific internal energy of 2864 kJ/kg and a specific volume of 0.03432 m3/kg. Its specific enthalpy (in kJ/kg) is _______

A closed system contains 10 kg of saturated liquid ammonia at 10°C. Heat addition required to convert the entire liquid into saturated vapour at a constant pressure is 16.2 MJ. If the entropy of the saturated liquid is 0.88 kJ/kg.K, the entropy (in kJ/kg.K) of saturated vapour is _______

Specific enthalpy and velocity of steam at inlet and exit of a steam turbine, running under steady state, are as given below:

 Specific enthalpy (kJ/kg) Velocity (m/s) Inlet steam condition 3250 180 Exit steam condition 2360 5

The rate of heat loss from the turbine per kg of steam flow rate is 5 kW. Neglecting changes in potential energy of steam, the power developed in kW by the steam turbine per kg of steam flow rate, is

In the figure shown, the system is a pure substance kept in a piston-cylinder arrangement. The system is initially a two-phase mixture containing 1 kg of liquid and 0.03 kg of vapour at a pressure of 100 kPa. Initially, the piston rests on a set of stops, as shown in the figure. A pressure of 200kPa is required to exactly balance the weight of the piston and the outside atmospheric pressure. Heat transfer takes place into the system until its volume increases by 50%. Heat transfer to the system occurs in such a manner that the piston, when allowed to move, does so in a very slow (quasi – static / quasi – equilibrium) process. The thermal reservoir from which heat is transferred to the system has a temperature of 400oC. Average temperature of the system boundary can be taken as 175oC. The heat transfer to the system is 1 kJ, during which its entropy increase by 10 J/K.

Specific volume of liquid (vf) and vapour (vg)  phases, as well as values of saturation temperatures, are given in the below.

 Pressure (kPa) Saturation Temperature, Tsat(oC) vf(m3/kg) vg(m3/kg) 100 100 0.001 0.1 200 200 0.0015 0.002

At the end of the process, which one of the following situations will be true?

In the figure shown, the system is a pure substance kept in a piston-cylinder arrangement. The system is initially a two-phase mixture containing 1 kg of liquid and 0.03 kg of vapour at a pressure of 100 kPa. Initially, the piston rests on a set of stops, as shown in the figure. A pressure of 200kPa is required to exactly balance the weight of the piston and the outside atmospheric pressure. Heat transfer takes place into the system until its volume increases by 50%. Heat transfer to the system occurs in such a manner that the piston, when allowed to move, does so in a very slow (quasi – static / quasi – equilibrium) process. The thermal reservoir from which heat is transferred to the system has a temperature of 400oC. Average temperature of the system boundary can be taken as 175oC. The heat transfer to the system is 1 kJ, during which its entropy increase by 10 J/K.

Specific volume of liquid (vf) and vapour (vg)  phases, as well as values of saturation temperatures, are given in the below.

 Pressure (kPa) Saturation Temperature, Tsat(oC) vf(m3/kg) vg(m3/kg) 100 100 0.001 0.1 200 200 0.0015 0.002

The work done by the system during the process is

In the figure shown, the system is a pure substance kept in a piston-cylinder arrangement. The system is initially a two-phase mixture containing 1 kg of liquid and 0.03 kg of vapour at a pressure of 100 kPa. Initially, the piston rests on a set of stops, as shown in the figure. A pressure of 200kPa is required to exactly balance the weight of the piston and the outside atmospheric pressure. Heat transfer takes place into the system until its volume increases by 50%. Heat transfer to the system occurs in such a manner that the piston, when allowed to move, does so in a very slow (quasi – static / quasi – equilibrium) process. The thermal reservoir from which heat is transferred to the system has a temperature of 400oC. Average temperature of the system boundary can be taken as 175oC. The heat transfer to the system is 1 kJ, during which its entropy increase by 10 J/K.

Specific volume of liquid (vf) and vapour (vg)  phases, as well as values of saturation temperatures, are given in the below.

 Pressure (kPa) Saturation Temperature, Tsat(oC) vf(m3/kg) vg(m3/kg) 100 100 0.001 0.1 200 200 0.0015 0.002

The net entropy generation (considering the system and the thermal reservoir together) during the process is closest to

Water has a critical specific volume of 0.003155 m3/kg. A closed and rigid steel tank of volume 0.025 m3 contains a mixture of water and steam at 0.1 MPa. The mass of the mixture is 10 kg. The tank is now slowly heated. The liquid level inside the tank