The
first law of thermodynamics takes the form W = ΔH when applied to
(A) A closed system undergoing a reversible
adiabatic process
(B) An
open system undergoing an adiabatic process with negligible changes in kinetic
and potential energies
(C) A closed system undergoing a reversible
constant volume process
(D) A closed system undergoing a reversible
constant pressure process
GATE
1993
Answer: (B)
A
reversible heat transfer demands
(A) The temperature difference causing heat
transfer tends to zero
(B) The system receiving heat must be at
constant temperature
(C) The system transferring out heat must be
at constant temperature
(D) Both interacting must be at constant
temperature
GATE
1993
Answer: (A)
Which
among the following relations is/are valid only for reversible process
undergone by a pure substance?
(A) dQ = dU + dW
(B) TdS = dU + dW
(C) TdS = dU + PdV
(D) dQ = PdV + dU
GATE
1993
Answer: (C)
When
a system undergoes an irreversible cycle
GATE
1993
Answer: (A)
The
second law of thermodynamics states that
(A) The energy change of a system undergoing
any reversible process is zero
(B) It is possible to transfer heat from a
lower temperature to a higher temperature
(C) The total energy of the system and
surroundings remains constant
(D) None of these
GATE
1994
Answer: (B)
A
closed system is cooled from 100⁰C to 50⁰C.
If no work is done on the system
(A) Its internal energy (U) decreases and its
entropy (S) increases
(B) U and S both decreases
(C) U decreases but S is constant
(D) U is constant but S decreases
GATE
1995
Answer: (B)
Calculate the
change in entropy when one gram of ice at 0⁰C in converted
into steam at 100⁰C. The latent heat of
fusion of ice = 80 cal/g. Latent heat of vaporization = 540 cal/g and the mean
specific heat of water between 0⁰C and 100⁰C
= 1 cal/g.⁰C.
(A) 2.05 cal/g. ⁰C
(B) 2.65 cal/g. ⁰C
(C) 3.25 cal/g. ⁰C
(D) 3.50 cal/g. ⁰C
GATE
1995
Answer: (A)
At inversion point Joule-Thomson
coefficient is
(A) Highly positive
(B) Highly negative
(C) Very small
(D) Zero
GATE
1995
Answer: (D)
The
kinetic energy of gas molecules is zero at
(A) 0⁰C
(B) 273⁰C
(C) 100⁰C
(D) -273⁰C
GATE
1995
Answer: (D)
The
equation dU=TdS-PdV is applicable to infinitesimal changes occurring in
(A) An open system of crystal composition
(B) A closed system of constant composition
(C) An open system with changes in
composition
(D) A closed system with changes in
composition
GATE
1996
Answer: (B)
The
number of degrees of freedom for a mixture of ice and water (liquid) are
(A) 2
(B) 3
(C) 1
(D) 0
GATE
1996
Answer: (A)
The
theoretical minimum work required to separate one mole of a liquid mixture at 1
atm, containing 50 mole% each of n-heptane and n-octane into pure components
each at 1 atm is
(A) -2RTln0.5
(B) -RTl0.5
(C) 0.5RT
(D) 2RT
GATE
1996
Answer: (B)
A
system undergoes a change from a given initial state to final state either by
an irreversible process or by a reversible process. Then
(A) ΔSI is always > ΔSR
(B) ΔSI is sometimes > ΔSR
(C) ΔSI is always < ΔSR
(D) ΔSI is always = ΔSR
Where,
ΔSI and ΔSR are the entropy changes of system for the
irreversible and reversible processes respectively.
GATE
1997
Answer: (D)
An equimolar mixture of benzene and
toluene is contained in a piston/cylinder arrangement at a temperature T. What
is the maximum pressure below which this mixture will exist as a vapour phase
alone? At a given T, the vapour pressure benzene and toluene are 1530 and 640
mm Hg respectively. Assume that Raoult’s law is valid
(A) 903 mm Hg
(B) 907 mm Hg
(C) 910 mm Hg
(D) 920 mm Hg
GATE
1997
Answer: (A)
The equilibrium constant k for a
chemical reaction depends on
(A) Temperature only
(B) Pressure only
(C) Temperature and pressure
(D) Ratio of reactants
GATE
1997
Answer: (A)
The decomposition of A into b is
represented by the exothermic reaction A↔B. To achieve maximum decomposition,
it is desirable to carry out the reaction.
(A) At high P and high T
(B) At low P and high P
(C) At low P and low T
(D) At high P and low T
GATE
1997
Answer: (D)
The
change in Gibb’s free energy for vaporization of a pure substance is
(A) Positive
(B) Negative
(C) Zero
(D) May be positive or negative
GATE
1997
Answer: (C)
A change in state involving a
decrease in entropy can be spontaneous only if
(A) It is exothermic
(B) It is isenthalpic
(C) It takes place isothermally
(D) It takes place at constant volume
GATE
1998
Answer: (A)
It
is desired to bring about certain change in the state of a system by performing
work on the system under adiabatic conditions
(A) The amount of work needed is
path-dependent
(B) Work alone cannot bring about such a
change of state
(C) The amount of work needed independent of
path
(D) More
information is needed to conclude about the path dependence or otherwise the
work needed
GATE
1998
Answer: (C)
A
carnot cycle consists of the following steps
(A) Two isothermal and two isentropics
(B) Two isobarics and two isothermals
(C) Two isochorics and two isobarics
(D) Two isothermals and two isochorics
GATE
1998
Answer: (A)
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