A
saturated liquid at 1500 kPa and 500 K, with an enthalpy of 750 kJ/kg, is
throttled to a liquid-vapour mixture at 150 kPa and 300 K. At the exit
conditions, the enthalpy of the saturated liquid is 500 kJ/kg and the enthalpy
of the saturated vapour is 2500 kJ/kg. The percentage of the original liquid,
which vaporizes, is
(A)
87.5%
(B)
67%
(C)
12.5%
(D)
10%
GATE
2010
Answer: (C)
A
new linear temperature scale, denoted by ⁰S, has been developed, where the
freezing point of water is 200⁰S
and the boiling point is 400⁰S.
On this scale, 500⁰S
corresponds, in degrees Celsius, to
(A)
100⁰C
(B)
125⁰C
(C)
150⁰C
(D)
300⁰C
GATE
2010
Answer: (C)
One
mole of methane is contained in a leak proof piston-cylinder assembly at 8 bar
and 1000 K. the gas undergoes isothermal expansion to 4 bar under reversible
conditions. Methane can be considered as an ideal gas under these conditions.
The value of universal gas constant is 8.314 J mol-1 K-1.
The heat transferred (in kJ) during the process is
(A)
11.52
(B)
5.76
(C)
4.15
(D)
2.38
GATE
2011
Answer: (B)
In a parallel
flow heat exchanger operating under steady state, hot liquid enters at a
temperature Th,in and leaves at a temperature Th,out.
Cold liquid enters at a temperature Tc,in and leaves at a
temperature Tc,out. Neglect any heat loss from the heat exchanger to
the surrounding. If Th,in>>Tc,in, then for a given
time interval, which one of the following statements is true?
(A)
Entropy gained by cold stream is greater
than entropy lost by hot stream
(B)
Entropy gained by cold stream is equal
than entropy lost by hot stream
(C)
Entropy by cold stream is less than
entropy lost by hot stream
(D)
Entropy gained by cold stream is zero
GATE
2012
Answer: (A)
An insulated,
evacuated container is connected to a supply line of an ideal gas at pressure Ps,
temperature Ts, and specific volume Vs. The container is
filled with the gas until the pressure in the container reaches Ps.
There is no heat transfer between the supply line to the container, and kinetic
and potential energies are negligible. If Cp and Cv are
the heat capacities at constant pressure and constant volume, respectively (γ =
Cp/Cv), then the final temperature of the gas in the
container is
(A)
γTs
(B)
Ts
(C)
(γ-1)Ts
(D)
(γ-1)Ts/γ
GATE 2012
Answer: (A)
In a throttling
process, the pressure of an ideal gas reduces by 50%. If cp and Cv
are the heat capacities at constant pressure and constant volume, respectively
(γ = Cp/Cv), the specific volume will change by a factor
of
(A)
2
(B)
21/γ
(C)
2γ-1/γ
(D)
0.5
GATE
2012
Answer: (A)
The
thermodynamic state of a closed system containing a pure fluid changes from (T1,
p1) to (T2, p2), where T and P denote the
temperature and pressure, respectively. Let, Q denote the heat absorbed (> 0
if absorbed by the system) and W the work done (> 0 if done by the system).
Neglect changes in kinetic and potential energies. Which one of the following
is correct?
(A)
Q is path-independent and W is
path-dependent
(B)
Q is path-dependent and W is
path-independent
(C)
(Q - W) is path-independent
(D)
(Q + W) is path-independent
GATE
2013
Answer: (C)
In
a closed system, the isentropic expansion of an ideal gas with constant
specific heats is represented by
GATE
2014
Answer: (D)
An ideal gas is
initially at a pressure of 0.1 MPa and a total volume of 2 m3. It is
first compressed to 1 MPa by a reversible adiabatic process and then cooled at
constant pressure to final volume of 0.2 m3. The total work done (in
kJ) on the gas for the entire process (upto one decimal place) is _________.
Data: R = 8.314
J/mol.K; heat capacity at constant pressure (Cp) = 2.5R
GATE
2015
Answer: 393.22
An ideal
gas is adiabatically and irreversibly compressed from 3 bar and 300 K to 6 bar
in a closed system. The work required for the irreversible compression is 1.5
times the work that is required for reversible compression from the same
initial temperature and pressure to the same final pressure. The molar heat
capacity of the gas at constant volume is 30 J mol‒1 K‒1
(assumed to be independent of temperature); universal gas constant, R is
8.314 J mol‒1 K‒1; ratio of molar heat capacities is
1.277. The temperature (in K, rounded off to the first decimal place) of the
gas at the final state in the irreversible compression case is _______.
GATE
2016
Answer: 373
A gas
obeying the Clausius equation of state is isothermally compressed from 5 MPa to
15 MPa in a closed system at 400 K. The Clausius equation of state is P =
RT/[v-b(T)] where P is the pressure, T is the temperature, v is the molar
volume and R is the universal gas constant. The parameter b in the above
equation varies with temperature as b(T) = b0+b1T with b0
= 4×10-5 m3mol-1 and b1 = 1.35×10-7
m3mol-1K-1. The effect of pressure on the
molar enthalpy (h) at a constant temperature is given by (∂h/∂P)T =
v – T(∂v/∂T)P. Let hi and hf denote the
initial and final molar enthalpies, respectively. The change in the molar
enthalpy hf – hi (in J mol-1, rounded off to
the first decimal place) for this process is ____________.
GATE
2016
Answer: 400
A binary system at a constant pressure
with species ‘1’ and ‘2’ is described by the two-suffix Margules equation, gE/RT
= 3x1x2, where gE is the molar Gibbs free
energy, R is the universal gas constant, T is the temperature and x1,
x2 are the mole fractions of species 1 and 2, respectively. At a
temperature T, g1/RT = 1 and g2/RT = 2, where g1
and g2 are the molar Gibbs free energies of pure species 1 and 2,
respectively. At the same temperature, g represents the molar Gibbs free energy
of the mixture. For a binary mixture with 40 mole% of species 1, the value
(rounded off to the second decimal place) of g/RT is ________.
GATE
2016
Answer: 1.65
An ideal
gas is adiabatically and irreversibly compressed from 3 bar and 300 K to 6 bar
in a closed system. The work required for the irreversible compression is 1.5
times the work that is required for reversible compression from the same initial
temperature and pressure to the same final pressure. The molar heat capacity of
the gas at constant volume is 30 J mol‒1 K‒1 (assumed to
be independent of temperature); universal gas constant, R is 8.314 J mol‒1
K‒1; ratio of molar heat capacities is 1.277. The temperature (in K,
rounded off to the first decimal place) of the gas at the final state in the
irreversible compression case is _______.
GATE
2016
Answer: 373
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