4131 + Interview Questions in THERMODYNAMICS IN GENERAL AWARENESS Page 37 InterviewSolution

1801.	A gas absorbs `200J` of heat and expands against the external pressure of `1.5 atm` from a volume of `0.5` litre to `1.0` litre. Calculate the change in internal energy.
Answer» `w=-PDeltaU` `=-1.5xx(1.0-0.5)` `=-0.75` litre atm `=-0.75xx101.3 J` `:. 1` liter -atm `=101.3 J` Now, `DeltaU=200-75.975` `=+124.025 J`

Discussion

1802.	If a gas absorbs `200J` of heat and expands by `500 cm^(3)` against a constant pressure of `2 xx 10^(5) N m^(-2)`, then the change in internal energy isA. `-300 J`B. `-100 J`C. `+100 J`D. `+300 J`
Answer» `DeltaU = q - w =q -P DeltaV` `= 200 -2xx 10^(5) xx 500 xx10^(-6)` `= 100J`

Discussion

1803.	Specific heat capacity of water isA. 4.186 J `g^(-1)K^(-1)`B. 4186 J `g^(-1)K^(-1)`C. 4.186 kJ `g^(-1)K^(-1)`D. 4186 kJ `g^(-1)K^(-1)`
Answer» Correct Answer - A

Discussion

1804.	The value of `C_(V)` for monatomic gas is `(3)/(2)R`, then `C_(P)` will beA. `(1)/(2)R`B. `(7)/(2)R`C. `(5)/(2)R`D. `(3)/(2)R`
Answer» Correct Answer - C

Discussion

1805.	A process can be reversible ifA. it is quasi-staticB. non-dissipativeC. Both (1) and (2)D. Neither (1) nor (2)
Answer» Correct Answer - C

Discussion

1806.	Adiabatic expansion of a gas causesA. CoolingB. HeatingC. No temperature changeD. Zero work done
Answer» Correct Answer - A

Discussion

1807.	The internal energy of non-ideal gas depends onA. TemperatureB. PressureC. VolumeD. All of these
Answer» Correct Answer - D

Discussion

1808.	In practise, all heat engines have efficiency less than that of a carnot engine becauseA. Carnot engine is irreversibleB. A reversible process can never be attained in a real worldC. Irreversible engine has higher efficiency than reversible engineD. Efficiency of carnot engine is always one
Answer» Correct Answer - B

Discussion

1809.	The effiency of reversible engine is___the irreversible engine.A. Less thanB. Greater thanC. Equal toD. Negligible than
Answer» Correct Answer - B

Discussion

1810.	A carnot cycle consists ofA. Two stagesB. Four stagesC. Six stagesD. Eight stages
Answer» Correct Answer - B

Discussion

1811.	The internal energy of an ideal gas increases when itA. ExpandsB. Is compressedC. Is first expanded and then compressedD. None of these
Answer» Correct Answer - D

Discussion

1812.	When are the two bodies in thermal equilibrium?
Answer» The two bodies are in thermal equilibrium if there is no wchange of theat between them.

Discussion

1813.	State true or false, internal energy of a gaseous system depends upon thermodynamic process.
Answer» False, it only depends on initial and final temperature.

Discussion

1814.	One mole of an ideal monoatomic gas undergoes the process `T=T_(0)+4V`, where `T_(0)` is initial temperature. Find (i) Heat capacity of gas as function of its volume. (ii) The amount of heat transferred to gas if its volume increases from `V_(0)` to `4V_(0)`.
Answer» (i) `C=(R)/(4)(10+(T_(0))/(V))` (ii) `Q=30RV_(0)+RT_(0)ln4`

Discussion

1815.	An ideal monoatomic gas goes through a cyclic process. Ratio of maximum temperature and minimum temperature is 2. find efficiency of cycle. .
Answer» Correct Answer - `eta=5%`

Discussion

1816.	Two moles of an ideal gas are contained in a vertical cylinder with a frictionless piston. The piston is slowly displaced so that expansionin gas is isothermal at temperature `T_(0)=400`K. find the amount of work done in increasing the volume to 3 times.t ake atmospheric pressure `=10^(5)N//m^(2)`
Answer» Correct Answer - 800 R ln (3)

Discussion

1817.	What are the values of pressure and temperature at the triple point of water?
Answer» The values of pressure and temperature at the triple point of water are 0.46 cm of Hg and 0.01°C respectively.

Discussion

1818.	What is the important difference between P.V. diagram of water and that of CO2?
Answer» The slope of fusion curve in negative in case of water, while it is positive in case of CO₂.

Discussion

1819.	Heat is supplied to a system, but its internal energy does not increases. What process is involved?
Answer» It happens during the isothermal expansion.

Discussion

1820.	What is the change in the internal energy of a gas, which is compressed isothermally?
Answer» Zero is the change in the internal energy of a gas, which is compressed isothermally.

Discussion

1821.	State Kirchhoff’s law.
Answer» It states that at a given temperature, the ratio of emissive power to absorb power corresponding to a given wavelength is constant for all bodies.

Discussion

1822.	Heat is supplied to a system, but the system does not perform any external work. What is the process involved?
Answer» It happens during an isochoric change.

Discussion

1823.	Explain, why a gas can only expand to constant temperature, if a certain quantity of heat is supplied to it :
Answer» When a gas expands, its temperature tends to fall. The heat supplied to the gas must be just enough to keep its temperature constant.

Discussion

1824.	List typical observations which are expected at absolute zero.
Answer» At absolute zero, we expect the following : (i) All molecular motions must cease. (ii) All metals must lose resistance and not get heated by electric current.

1824.

List typical observations which are expected at absolute zero.

Answer»

At absolute zero, we expect the following :

(i) All molecular motions must cease.

(ii) All metals must lose resistance and not get heated by electric current.

Discussion

1825.	What is mean kinetic energy of molecule per unit volume?
Answer» The mean kinetic energy of the molecules per unit volume is 3/2 P.

Discussion

1826.	Is the equation PV = RT valid for both isothermal and adiabatic changes?
Answer» No, for adiabatic changes equation would be PV^γ = constant, while PV = RT is valid for isothermal changes.

Discussion

1827.	Name the forces in a system which make the process taking place in it, irreversible in a nature.
Answer» All types of dissipative forces in a system make the process taking place irreversible. Force of friction is an example of dissipative force.

Discussion

1828.	What is the total energy possess by molecules of an ideal gas?
Answer» Since, in an ideal gas, there is no molecular attraction, the P.E. of the molecules is zero. Therefore, internal energy of an ideal gas is only kinetic in nature.

Discussion

1829.	When an inflated tyre bursts, then why does the escaping air get cooled?
Answer» Air expands on sudden bursting of tyre which is an adiabatic process. Air does work against atmosphere at the cost of its own internal energy.

Discussion

1830.	It is possible that there is a change in temperature of a body without any heat exchange with it?
Answer» Yes, it happens in an adiabatic process.

Discussion

1831.	Give the types of the internal energies of a substance.
Answer» There are two types of internal energies of a substance : (i) Internal kinetic energy denoted by U_k. (ii) Internal potential energy denoted by U_p.

1831.

Give the types of the internal energies of a substance.

Answer»

There are two types of internal energies of a substance :

(i) Internal kinetic energy denoted by U_k.

(ii) Internal potential energy denoted by U_p.

Discussion

1832.	What is the nature of `P-V` diagram for isobaric and isochoric processes?
Answer» In an isobaric process, the `P-V` diagram is an straight line parallel to volume axis. In an isochoric process, the `P-V` diagram is a straight line parallel to pressure axis

Discussion

1833.	Mention two essential characteristics of an ideal heat engine.
Answer» (i) It should have a source of infinite thermal capacity. (ii) It should have a sink of infinite thermal capacity.

1833.

Mention two essential characteristics of an ideal heat engine.

Answer»

(i) It should have a source of infinite thermal capacity.

(ii) It should have a sink of infinite thermal capacity.

Discussion

1834.	What is the nature of P-V diagram for isobaric and isochoric processes?
Answer» The P-V diagram for an isobaric change is a straight line parallel to volume axis, while that for an isochoric process, it is a straight line parallel to pressure axis.

Discussion

1835.	Can heat be completely converted into work?
Answer» No, heat Cannot be completely converted into work.

Discussion

1836.	What is the nature of P-V diagram for isobaric and isochoric process?
Answer» The P-V diagram for an isobaric process is a straight line parrel to the volume axis while that For an isochoric process is a straight line parallel to pressure axis.

Discussion

1837.	On what factors does the efficiency of Carnot engine depends?
Answer» Temperature of the source of heat and sink.

Discussion

1838.	It is planned to carry the reaction `CaCO_(3)(s) hArr CaO (s) +CO_(2)(g)` at 1273K and 1 bar (a) Is this reaction spontaneous at this temperature and pressure ? (b) Calculate the value of (i) `K_(p)` at 1273 K for the reaction and (ii) partial pressure of `CO_(2)` at equilibrium Given `Delta_(f) H^(@)` values (`kJ mol^(-1)) :` `CaCO_(3)(s) =-1206.9, CaO(s)= - 635.1, CO_(2)(g) = - 393.5` `S^(@) ` value `(JK^(-1) mol^(-1))` `CaCO_(3)(s) =92.9, CaO(s) = 39.8, CO_(2)(g) = 213.7`.
Answer» (a) `Delta_(r) H^(@) = Delta_(f) H^(@) ( CaO) +Delta_(f)H^(@) ( CO_(2))]-[Delta_(f)H^(@) ( CaCO_(3))]` `= [ - 635.1 + ( -393.5) ] - ( - 1206.9 )= + 178.3 kJ mol^(-1)` `Delta_(r)S^(@) = [S^(@) ( CaO) + S^(@) ( CO_(2)) ] - [S^(@)(CaCO_(3))]` `= ( 39.8 +213 .7)- 92.9= + 160.6 JK^(-1) mol^(-1)` `Delta_(r)G^(@) =Delta_(r)H^(@) - T Delta_(r)S^(@)` `= 178300 Jmol^(-1) - 1273 K xx 160.6 JK^(-1) mol^(-1)` `= - 26143.8 J mol^(-1) = 26144 mol^(-1) = 26.1 kJ mol^(-1)` As `Delta_(r) G^(@)` is negative, hence the reaction is spontaneous (b)(i) `DeltaG^(@) = - 2.303 RT log K_(p)` or `log K_(p) = ( - 26144 J mol^(-1))/( 2.303 xx 8.314 JK^(-1) xx 1273 K )` `= 1.0726` `K_(p) =` Antilog `1.0726 = 11.82` Applying law of chemical equilibrium `K_(p) = p_(CO_(2)) = 11.82` bar

Discussion

1839.	Which of the following conditions should be satisfied for the given reaction to be spontaneous at `0^(@)C` and 1 atm ? `H_(2)O(s) hArr H_(2)O(l)`A. `Delta H = Delta G`B. `Delta H lt T Delta S`C. `Delta H gt T Delta S`D. `Delta H = T Delta S`
Answer» Correct Answer - B

Discussion

1840.	Which of the following represents heat of formation `(Delta H_(f))` ?A. `C("diamond") + O_(2)(g) rarr CO_(2)(g)`B. `2CO(g) + O_(2)(g) rarr 2CO_(2)(g)`C. `(1)/(2) H_(2)(g) + (1)/(2) F_(2)(g) rarr HF(g)`D. `N_(2)(g) + 3H_(2)(g) rarr 2NH_(3)(g)`
Answer» Correct Answer - C

Discussion

1841.	1 mole of an ideal gas is expanded from an initial pressure of 1 bar to final pressure of 0.1 bar at constant temperature of 273 K. Predict which of the following is not true?A. `Delta`E = 0B. `Delta`H = 0C. PV is constantD. `Delta S larr 0`
Answer» Correct Answer - D

Discussion

1842.	Predict sigh of work done in following reactions at constant pressure.
Answer» Correct Answer - (i) W, (ii) -W, (iii) -W, (iv)-W (i) `DeltaV = - ve rArr W = +ve` (ii) `DeltaV = + ve rArr W = -ve` (iii) `DeltaV = + ve rArr W = -ve` (iv) `DeltaV = + ve rArr W = -ve`

Discussion

1843.	Select the correct statement(s).A. For the equuilibrium pressure is constantB. For equilibrium temperature is constantC. For equilibrium `((delG)/(deln))_(P,T) ` is constantD. For equilibrium pressure & temperature is variable .
Answer» Correct Answer - A::B::C (A) Mechanical Equilibrium (B) Thermal Equilibrium (C) Chemical Equilibrium

Discussion

1844.	Which of the following statement (s)is / are false:A. `Delta_(r)S` for `(1)/(2) N_(2) (g) to N(g)` is positiveB. `DeltaG_("system")` is always zero for a reversible process in a clossed system.C. `DeltaG^(@)` for an ideal is a function of temperature and pressure.D. enthropy of a closed system maximized at equilibrium
Answer» Correct Answer - B::C::D

Discussion

1845.	In isothermal ideal gas compression :A. `W "is +ve"`B. `DeltaH` is zeroC. `DeltaS_(gas) "is +ve"`D. `DeltaG "is + ve"`
Answer» Correct Answer - A::B::D ` W is + ve`

Discussion

1846.	which is / are correct statement .A. `W_("adiabatic") gt W_("isothermal")` in an ideal gas compression from same initial state to same final volume .B. The value of `gamma(gamma= (C_(p))/(C_(v)))` remains constant for diatomic gas at all temperature .C. Entropy increases when an ideal gas expanded isothermally.D. `Delta_(r) H & Delta_(r)S` both are + ve for the decomposition of `MgCO_(3)` .
Answer» Correct Answer - A::C::D Slope of adiabatic cruve is `gamma` times of than slope of isothermal curve on PV diagram

Discussion

1847.	Which is the correct is /are correcct :A. Final temperature in reversible adiabatic expansion is lesser than in irreversible adiabatic expansion .B. When heat is supplied to an ideal gas in isothermal process, kinetic energy of gas will increasase.C. When an ideal gas is subjected to adiabatic expansion it gets cooledD. Entropy increases in atomisation of dihydrgen
Answer» Correct Answer - A::C::D `W_("irr")gtW_("rev") ` with sign `nC_(V) (T_("irr")-n T_(1))gt "nc"_("v")(T_("rev")-n T_(1))` `T_("irr")gtT_("rev")`

Discussion

1848.	These question consists of two statements each, printed as Statement-I and Statement-II . While answering these Question you are required to choose any one of the following four responses. Statement -I : Due to adiabatic expansion , temperature of an ideal gas always decreases. Statment -II : For an adiabatic expansion `DeltaU =W`.A. If both Statement -I & Statement are True & the Statement-II is a correct explanation of the Statement -IB. If both Statement -I & Statement are True & the Statement-II is not a correct explanation of the Statement -IC. If Statement-I is True but the Statement-II is False.D. If Statement-I is True but the Statement-II is True .
Answer» Correct Answer - D

Discussion

1849.	Which of the following is true for reversible adiabatic process involving an ideal gas ?A. Gas with higher`gamma` has high magnitude of slope in a `P ("y-axis" )v//s T ("x - axis" )` curveB. Gas with higher`gamma` has high magnitude of slope in a `V ("y-axis" )v//s T ("x - axis" )` curveC. Gas with higher`gamma` has high magnitude of slope in a `P ("y-axis" )v//s V ("x - axis" )` curveD. Gas with higher`gamma` has low magnitude of slope in a `P ("y-axis" )v//s T ("x - axis" )` curve
Answer» Correct Answer - C::D For P-T graph Magnetic of slope `= (gamma)/(rho-1)/(P)/(T)` `as gammauarr"slpoe"darr` For P- V graph Magnitude of slope =` (V)/(T)(1)/( gamma-1)` ` as gamma uarr slope darr`

Discussion

1850.	These question consists of two statements each, printed as Statement-I and Statement-II . While answering these Question you are required to choose any one of the following four responses. Statement -I : Due to adiabatic expansion , temperature of an ideal gas always decreases. Statment -II : For an adiabatic expansion `DeltaU =W`.A. If both Statement -I & Statement are True & the Statement-II is a correct explanation of the Statement -IB. If both Statement -I & Statement are True & the Statement-II is not a correct explanation of the Statement -IC. If Statement-I is True but the Statement-II is False.D. If Statement-I is True but the Statement-II is True .
Answer» Correct Answer - D

Discussion

Explore topic-wise InterviewSolutions in .

A gas absorbs `200J` of heat and expands against the external pressure of `1.5 atm` from a volume of `0.5` litre to `1.0` litre. Calculate the change in internal energy.

If a gas absorbs `200J` of heat and expands by `500 cm^(3)` against a constant pressure of `2 xx 10^(5) N m^(-2)`, then the change in internal energy isA. `-300 J`B. `-100 J`C. `+100 J`D. `+300 J`

Specific heat capacity of water isA. 4.186 J `g^(-1)K^(-1)`B. 4186 J `g^(-1)K^(-1)`C. 4.186 kJ `g^(-1)K^(-1)`D. 4186 kJ `g^(-1)K^(-1)`

The value of `C_(V)` for monatomic gas is `(3)/(2)R`, then `C_(P)` will beA. `(1)/(2)R`B. `(7)/(2)R`C. `(5)/(2)R`D. `(3)/(2)R`

A process can be reversible ifA. it is quasi-staticB. non-dissipativeC. Both (1) and (2)D. Neither (1) nor (2)

Adiabatic expansion of a gas causesA. CoolingB. HeatingC. No temperature changeD. Zero work done

The internal energy of non-ideal gas depends onA. TemperatureB. PressureC. VolumeD. All of these

In practise, all heat engines have efficiency less than that of a carnot engine becauseA. Carnot engine is irreversibleB. A reversible process can never be attained in a real worldC. Irreversible engine has higher efficiency than reversible engineD. Efficiency of carnot engine is always one

The effiency of reversible engine is___the irreversible engine.A. Less thanB. Greater thanC. Equal toD. Negligible than

A carnot cycle consists ofA. Two stagesB. Four stagesC. Six stagesD. Eight stages

The internal energy of an ideal gas increases when itA. ExpandsB. Is compressedC. Is first expanded and then compressedD. None of these

When are the two bodies in thermal equilibrium?

State true or false, internal energy of a gaseous system depends upon thermodynamic process.

One mole of an ideal monoatomic gas undergoes the process `T=T_(0)+4V`, where `T_(0)` is initial temperature. Find (i) Heat capacity of gas as function of its volume. (ii) The amount of heat transferred to gas if its volume increases from `V_(0)` to `4V_(0)`.

An ideal monoatomic gas goes through a cyclic process. Ratio of maximum temperature and minimum temperature is 2. find efficiency of cycle. .

Two moles of an ideal gas are contained in a vertical cylinder with a frictionless piston. The piston is slowly displaced so that expansionin gas is isothermal at temperature `T_(0)=400`K. find the amount of work done in increasing the volume to 3 times.t ake atmospheric pressure `=10^(5)N//m^(2)`

What are the values of pressure and temperature at the triple point of water?

What is the important difference between P.V. diagram of water and that of CO2?

Heat is supplied to a system, but its internal energy does not increases. What process is involved?

What is the change in the internal energy of a gas, which is compressed isothermally?

State Kirchhoff’s law.

Heat is supplied to a system, but the system does not perform any external work. What is the process involved?

Explain, why a gas can only expand to constant temperature, if a certain quantity of heat is supplied to it :

List typical observations which are expected at absolute zero.

What is mean kinetic energy of molecule per unit volume?

Is the equation PV = RT valid for both isothermal and adiabatic changes?

Name the forces in a system which make the process taking place in it, irreversible in a nature.

What is the total energy possess by molecules of an ideal gas?

When an inflated tyre bursts, then why does the escaping air get cooled?

It is possible that there is a change in temperature of a body without any heat exchange with it?

Give the types of the internal energies of a substance.

What is the nature of `P-V` diagram for isobaric and isochoric processes?

Mention two essential characteristics of an ideal heat engine.

What is the nature of P-V diagram for isobaric and isochoric processes?

Can heat be completely converted into work?

What is the nature of P-V diagram for isobaric and isochoric process?

On what factors does the efficiency of Carnot engine depends?

Which of the following conditions should be satisfied for the given reaction to be spontaneous at `0^(@)C` and 1 atm ? `H_(2)O(s) hArr H_(2)O(l)`A. `Delta H = Delta G`B. `Delta H lt T Delta S`C. `Delta H gt T Delta S`D. `Delta H = T Delta S`

Which of the following represents heat of formation `(Delta H_(f))` ?A. `C("diamond") + O_(2)(g) rarr CO_(2)(g)`B. `2CO(g) + O_(2)(g) rarr 2CO_(2)(g)`C. `(1)/(2) H_(2)(g) + (1)/(2) F_(2)(g) rarr HF(g)`D. `N_(2)(g) + 3H_(2)(g) rarr 2NH_(3)(g)`

1 mole of an ideal gas is expanded from an initial pressure of 1 bar to final pressure of 0.1 bar at constant temperature of 273 K. Predict which of the following is not true?A. `Delta`E = 0B. `Delta`H = 0C. PV is constantD. `Delta S larr 0`

Predict sigh of work done in following reactions at constant pressure.

Select the correct statement(s).A. For the equuilibrium pressure is constantB. For equilibrium temperature is constantC. For equilibrium `((delG)/(deln))_(P,T) ` is constantD. For equilibrium pressure & temperature is variable .

In isothermal ideal gas compression :A. `W "is +ve"`B. `DeltaH` is zeroC. `DeltaS_(gas) "is +ve"`D. `DeltaG "is + ve"`