4131 + Interview Questions in THERMODYNAMICS IN GENERAL AWARENESS Page 34 InterviewSolution

1651.	Gas with in a chamber, passes through the cycle shown in (figure). Determine the net heat added to the system during process AB is `Q_(AB)= 20J`. No heat is transferred during process BC and net work done during the cycle is `15J`
Answer» According to first law of thermodynamics. In process CA, `dQ_(CA)=dU_(CA)+dW_(CA)` In process AB `dQ_(AB)=dU_(AB)+dW_(AB)`, and In process BC `dQ_(BC)=dU_(BC)+dW_(BC)` Adding the three equations, we get `dQ_(CA)+dQ_(AB)+dQ_(BC)= (dU_(CA)+dU_(AB)+dU_(BC))` `+(dW_(CA)+dW_(AB)+dW_(BC)`....(i) As the process is cyclic, `dU=dU_(CA)+dU_(AB)+dU_(BC)=0` From (i) `dQ_(CA)+20+0=0+15` `dQ_(CA)=15-20= -5J` This is the net heat added to the system.

Discussion

1652.	Is the equation `PV=RT` valid for both, isothermal and adiabatic changes?
Answer» Yes, this equation is valid for all thermodynamical processes.

Discussion

1653.	Predict in which of the following, entropy increases:A. A liquid crystallizes into a solid.B. Temperature of a crystalline solid raised from 0 K to 115 K.C. `2NaHCO_(3)(s) rarr Na_(2)CO_(3)(s)+CO_(3)(g)+H_(2)O(g)`D. `H_(2)(g) rarr 2H(g)`
Answer» Correct Answer - B::C::D Increase in randomness increases the entropy.

Discussion

1654.	The vapour pressure of solid benzoic acid has been found to obey the relationship ( in the neighbourhood of 298 K) as: `ln.(P)/(P^(@)) = a-(b)/(T)`, where a = 22.88 and `b = 1.07 xx 10^(4)K` Which of the following values are correct at 298 K for the sublimation of benzoic acid?A. `Delta G^(@) = 32.34 kJ mol^(-1)`B. `Delta H^(@) = 88.96 kJ mol^(-1)`C. `Delta S^(@) = 190 JK^(-1) mol^(-1)`D. `Delta H^(@) = -88.96 kJ mol^(-1)`
Answer» Correct Answer - A::B::C `because P^(@) = 1 atm` `ln P = -b.(1)/(T) + a rArr ln K_(P) = -b.(1)/(T)+a` `P_(eq) = P_(("benzoic acid")) =K_(P)`

Discussion

1655.	For an ideal gas, consider only `P-V` work in going from an initial state `X` to the final state `Z`. The final state `Z` can be reached by either of the two paths shown in the figure. Which of the following choice(s) is (are) correct? [Take `DeltaS` as change in entropy and `w` as work done] A. `DeltaS_(XtoZ)=DeltaS_(XtoY)+DeltaS_(YtoZ)`B. `w_(XtoZ)=w_(XtoY)+w_(YtoZ)`C. `w_(XtoYtoZ)=w_(XtoY)`D. `DeltaS_(XtoYtoZ)=DeltaS_(XtoY)`
Answer» Correct Answer - A::C `DeltaS` is a state function. So, it does not depend on path and only depends on initial and final stages. `DeltaS_(XtoZ)=Delta_(XtoY)+DeltaS_(YtoZ)` and `DeltaS_(YtoZ)` is not zero `:. DeltaS_(XtoYtoZ)!=DeltaS_(XtoY)` Work is not a state function and depends on path, `:. w_(XtoZ)=w_(XtoY)+w_(YtoZ)` `w_(XtoZ)=PdV` (`P` constant) `w_(YtoZ)=0` (`V` is constant) `w_(XtoZ)=2.303nRT"log"(V_(2))/(V_(1))` `w_(XtoYtoZ)=w_(XtoY)+w_(YtoZ)` As `w_(YtoZ)=0`, hence `w_(XtoYtoZ)=w_(XtoY)`

Discussion

1656.	The gas in a refrigerator causes cooling on expansion because:A. Work done by the gas is converted into heatB. Heat of the gas is lost as work is done by the gasC. The heat is spread over a large spaceD. None of the above
Answer» Correct Answer - B Heat of the gas is lost as work is done by the gas

Discussion

1657.	A reaction proceeds through two paths I and II to convert `X rarr Z`. What is the correct relationship between `Q. Q_(1) and Q_(2)` ?A. `Q=Q_(1)xxQ_(2)`B. `Q=Q_(1)+Q_(2)`C. `Q=Q_(2)-Q_(1)`D. `Q=Q_(1)//Q_(2)`
Answer» Correct Answer - B

Discussion

1658.	Which of the following expressions is correct to calculate enthalpy of a reaction ?A. `DeltaH_("reaction")=SigmaDelta_(f)H_("reactions")-SigmaDelta_(f)H_("products")`B. `DeltaH_("reaction")=SigmaB.E._("products")-Sigma B.E._("reactants")`C. `DeltaH_("reaction")=SigmaB.E._("reactants")-SigmaB.E._("products")`D. `DeltaH_("reaction")=DeltaH_(1)xxDeltaH_(2)xxDeltaH_(3)...`
Answer» Correct Answer - C

Discussion

1659.	Thermodynamics mainly deals with:A. interrelation of various forms of energy and their transformation from one form to anotherB. energy changes in the processes which depends only on initial and final states of the microscopic system containing a few moleculesC. how and at what rate these energy transformations are carried outD. the system in equilibrium state or moving from one equilibrium state to another equilibrium state
Answer» Correct Answer - A::D Thermodynamics deals with interrelation of various forms of energy and their transformation into each other. It also deals with thermal or mechanical equilibrium. However, it does not tell anything about the rate of reaction.

Discussion

1660.	Which of the following is the correct option for the free expansion of an ideal gas under adiabatic condition?A. `q=0, Delta T ne = 0, w = 0`B. `q ne 0, Delta T = 0, w = 0`C. `q = 0, Delta T = 0, w = 0`D. `q = 0, Delta T lt 0, w ne 0`
Answer» Correct Answer - C

Discussion

1661.	In an isothermal process the volume of an ideal gas is halved. One can say thatA. Internal energy of the system decreasesB. Work done by the gas is positiveC. Work done by the gas is negativeD. Internal energy of the system increases
Answer» Correct Answer - C

Discussion

1662.	A thermodynamic process in which temperature T of the system remains constant though other variable P and V may change, is calledA. Isochoric processB. Isothermal processC. Isobaric processD. None of these
Answer» Correct Answer - B

Discussion

1663.	`At298 K,DeltaH_("combustion")^(@)("sucrose")=-5737"kJ"//"mol"` and `DeltaG_("combustion")^(@)("sucrose")=-6333"kJ"//"mol."` Estimate additional non-PV work that is obtainced by raising bemperature to `310` K. Assume `Delta_(r)Cp=0` for this temperature change.
Answer» Correct Answer - 24

Discussion

1664.	A gas expands from a valume of `3 dm^(3) " to " 30 dm^(3)` against a constant pressure of 7 bar at initially `27^(@)C`. The work done during expansion is used to heat, 50 moles of water. Calculate rise in temperature (K) of water. (Take specific heat capacity of `H_(2)O " as " 4.2 "J"//"gram-K"and 1 " litre bar" =100 J)`
Answer» Correct Answer - 5

Discussion

1665.	Calculate `DeltaG` (in bar-L) when a definite mass of a monoatomic ideal gas at 1 bar and `27^(@)C` is expanded adiabatically against vacuum from 10 L to 20 L (In 2=0.7).
Answer» Correct Answer - 7

Discussion

1666.	How much heat (in kJ) should be supplied to a rigid conducting vessel of volume V litres, so that 0.5 mole of C is formed in the reaction : `A(g)+B(g)to C(g),Delta H=+7.6kJ` Take `R= 8"J"//"K mole"`, T=300 K
Answer» Correct Answer - 5

Discussion

1667.	Which is a good fuel `CH_(4)` or `C_(2)H_(6)` ? The standard enthalpy of formation of`CH_(4),C_(2)H_(6),CO_(2)` and `H_(2)O` are -74.8, -84.6, -393.5 and -286kJ `mol^(-1)` respectively .
Answer» Correct Answer - `CH_(4)` Calculate `Delta H ` for `CH_(4) + 2O_(2) rarr CO_(2)+ 2H_(2)O` and `C_(2)H_(6) + ( 7)/( 2) O_(2) rarr 2CO_(2) + 3H_(2)O`. Then calculate `Delta H` per gram

Discussion

1668.	Calculate the enthalpy changewhen 2.38 g of carbonmonoxide ( CO) vaporize at its normal boiling point. Given that the enthalpy of vaporisation of carbon monoxide is6.04 kJ `mol^(-1)` at its normal boiling point of `82.0` K.
Answer» Correct Answer - `513.4J` `Delta_(vap) H ` for `CO = 6.04 kJ mol^(-1)`, i.e., = 6.04 kJ for28 g `:. `Enthalpy change for vaporisation of2.38 g `= ( 6.04) /( 28) xx2.38 kJ = 0.5134 kJ= 513.4 J`

Discussion

1669.	One mole of ideal gas expands freelt at 310 K from five litre volume to 10 litre volume. Then `Delta E` and `Delta H` of the process are respectivelyA. 0 and 5 calB. 0 and `5xx300` calC. 0 and 0D. 5 and 0 cal
Answer» Correct Answer - C Free expansion `W=0`. Since Temperature is constant `DeltaU=0, DeltaH=0`

Discussion

1670.	Red phosphorus reacts with liquid bromine in an exothermic reaction `2P(s) + 3 Br_(2) (l) rarr PBr_(3) (g), Delta_(r) H^(@) = - 243 kJ mol^(-1)` Calculated the enthalpy change when `2.63 g` of phosphorus reacts with an excess of bromine in this way.A. `10.3 kJ`B. `1536 kJ`C. `7.5 kJ`D. `20.3 kJ`
Answer» Correct Answer - A Calculate the number of moles of `P` and mulitply it with `Delta_(r) H^(@)` for 1 mol of `P`. `n_(P) = (Mass_(P))/(Molar mass_(P)) = (2.63 g)/(30.97 mol^(-1)) = 0.0849 of P` `Delta H = (0.0849 mol) ((-243 kJ)/(2 mol P))` `= 10.3 kJ`

Discussion

1671.	Define thermal efficiency of a heat engine.
Answer» The thermal efficiency, η of a heat engine is defined W as η = \(\frac{W}{Q_H}\), where W is the work done (output) by Q_H the working substance and Q_H is the amount of heat absorbed (input) by it. [Note : η has no unit and dimensions or its dimensions are [M°L°T°].]

1671.

Define thermal efficiency of a heat engine.

Answer»

The thermal efficiency, η of a heat engine is defined W as η = \(\frac{W}{Q_H}\), where W is the work done (output) by Q_H the working substance and Q_H is the amount of heat absorbed (input) by it.

[Note : η has no unit and dimensions or its dimensions are [M°L°T°].]

Discussion

1672.	In a cyclic process, the area enclosed by the loop in the P – V plane corresponds to (A) ∆U (B) W(C) Q – W (D) W – Q.
Answer» Correct option is (B) W

Discussion

1673.	The efficiency of a heat engine is given by η = (A) QH /W (B) W/QC (C) W/QH(D) QC /W.
Answer» Correct option is (C) W/Q_H

Discussion

1674.	In a cyclic process, (A) ∆U = Q (B) Q = 0 (C) W = 0 (D) W = Q
Answer» Correct option is (D) W = Q

Discussion

1675.	In an isobaric process, in the usual notation, (A) W = P (Vf – Vi) (B) W = Q (C) W = – ∆U (D) ∆T = 0.
Answer» (A) W = P (V_f – V_i)

Discussion

1676.	In an adiabatic process, in the usual notation, W =(A) \(\frac{P_iV_i-P_fV_f}{\gamma-1}\)(B) \(\frac{nR∆T}\gamma\)(C) nR\(\gamma\)(Ti - Tf)(D) \(\frac{P_iV_i-P_fV_f}{\gamma}\)
Answer» (A) \(\frac{P_iV_i-P_fV_f}{\gamma-1}\)

Discussion

1677.	In an adiabatic process, in the usual notation, (A) TVγ = constant (B) PTγ = constant (C) W = 0 (D) PVγ = constant.
Answer» (D) PV^γ = constant.

Discussion

1678.	In an adiabatic process, in the usual notation, (A) ∆ P = 0 (B) ∆ V = 0 (C) Q = 0 (D) ∆U = 0.
Answer» Correct option is (C) Q = 0

Discussion

1679.	In an isobaric process, in the usual notation, (A) W = nCv (Tf – Ti) (B) Q = nCp (Tf – Ti) (C) ∆U = nR (Tf – Ti) (D) W = 0.
Answer» (B) Q =_nC_p (T_f – T_i)

Discussion

1680.	In the usual notation, the isothermal work, W = (A) P(Vf – Vi) (B) nRT(Pi/ Pf) (C) nRT ln(Pi/Pf) (D) nRT(Pf/Pi).
Answer» (C) nRT ln(P_i/P_f)

Discussion

1681.	In an isothermal process, in the usual notation, (A) W = nRT (V /V ) (B) W = ∆ U (C) W = Q (D) W = 0.
Answer» Correct option is (C) W = Q

Discussion

1682.	In an isothermal process, in the usual notation, (A) W = P(Vf – Vi)(B) W = 0 (C) W = V(Pf – Pi) (D) W = nRT In(Vf/Vi).
Answer» (D) W = nRT In(V_f/V_i).

Discussion

1683.	In an isothermal process, in the usual notation, (A) PV = constant(B) V/T = constant (C) P/T = constant (D) Q = 0.
Answer» (A) PV = constant

Discussion

1684.	According to the first law of thermodynamics, in the usual notation, (A) Q = ∆U + W (B) Q = ∆U – W (C) Q = W – ∆U (D) Q= -(∆ U + W).
Answer» (A) Q = ∆U + W

Discussion

1685.	In isothermic process, which statement is wrongA. Temperature is constantB. Internal energy is constanC. No exchange of energyD. (a) and (b) are correct
Answer» Correct Answer - C

Discussion

1686.	The external pressure `2` atm is applied on frictionless movable piston, fitted in a vessel containing `100` g of X(g) at `450` K. now heat is sulplied keeping pressure constant till `40` g of Xis evaporated to to from X(g) at `500` K (boinling poing ). Calculate change in internal `(DeltaU)` energy in kJ for overall process. Assume vapour of X (l) behaves like an ideal gas. Given : Molar hect capacity of X (l) =`60` J/mol K: `DeltaH_("vaporisation")`=30kJ/mol,`DeltaH_("vaporisation")`=30kJ/mol,R=8.3J/mol-K At weight of X = `20 g//mol`.
Answer» Correct Answer - 6670

Discussion

1687.	Explain heat of neutralisation with an example.
Answer» Heat of neutralisation is the change in enthalpy produced when one gram equivalent weight of an acid is neutralised by one gram equivalent weight of a base in dilute solution. Example : HCl(aq) + NaOH(aq) → NaCl(aq) + H₂O;= ΔH – 57.3 kJ

1687.

Explain heat of neutralisation with an example.

Answer»

Heat of neutralisation is the change in enthalpy produced when one gram equivalent weight of an acid is neutralised by one gram equivalent weight of a base in dilute solution.

Example : HCl(aq) + NaOH(aq) → NaCl(aq) + H₂O;= ΔH – 57.3 kJ

Discussion

1688.	Assertion: Specific heat of a body is always greater than its thermal capacity. Reason: Thermal capacity is the heat required for raising temperature of unit mass of the body through unit degreeA. If both, Assertion and Reason are true and Reason is the correct explanation of the Asserrion.B. If both,Assertion and Reason are true but Reason is not a correct explanation of the Assertion.C. If Assertion is true but the Reason is false.D. If both, Assertion and Reason are false.
Answer» Correct Answer - D Infact,specific heat of a body is the amount of heat required to raise the temperature of unit mass of the body through unit degree. When mass of a body is less than unity, its thermal capacity is less than its specific heat and vice-versa.

Discussion

1689.	For is process involiving solids `and//or` liquids,A. `Delta H gt Delta U`B. `Delta H lt Delta U`C. `Delta H = Delta U = 0`D. `Delta H ~= Delta U`
Answer» Correct Answer - D Because `Delta H = Delta U + P Delta V` and for a process involving solids and/or liqiuds, `Delta V ~= 0`.

Discussion

1690.	Knowing the viscosity coefficient of helium under standard conditions, calculate the effective diameter of the helium atom.
Answer» `eta = (1)/(3) sqrt((8 kT)/(pi m)) (m)/(sqrt(2) pi d^2) = (2)/(3) sqrt((m kT)/(pi^3)) (1)/(d^2)` or `d = ((2)/(3 eta))^(1//2) ((mkT)/(pi^3))^(1//4) = ((2)/(3 xx 18.9) xx 10^6)^(1//2) ((4 xx 8.31 xx 273 xx 10^-3)/(pi^3 xx 36 xx 10^46))^(1//4)` =`10^10 ((2)/(3 xx 18.9))^(1//2) ((4 xx 83.1 xx 273)/(pi^3 xx .36))^(1//4) ~~ 0.178 nm`.

Discussion

1691.	Which of the following statements is correct?A. The presence of reacting species in a covered beaker is an example of open system.B. There is an exchange of energy as well as matter between the system and the surroundings in a closed system.C. The presnce of reactants in a closed vessel made up of copper is an example of a closed system.D. The presence of reactants in a thermos flask or any other closed insulated vessel is an example of a closed system.
Answer» Correct Answer - C In a closed system (e.g., the presence of reactants in a closed vessel made of conducting material i.e. copper ) there is no exchange of matter, but exchange of energy is possible between system and the surroundings.

Discussion

1692.	A system consists of a gas contined in a thin ballon. If the ballon deflates as the temperature of the gas changes from `90^(@)C "to"25^(@)C`, then:A. Heat is transferred out of the system and work is done on the system.B. Heat is transferred out of the system and work is done by the system.C. Heat is transferred into the system and work is done by the system.D. Heat is transferred into the system and work is done the system
Answer» Correct Answer - A

Discussion

1693.	Thermodynamics is not concerned about ________.A. energy changes involved in a chemical reactionB. the extent to which a chemical reaction proceedsC. the rate at which a reaction proceedsD. the feasibility of a chemical reaction
Answer» Correct Answer - C Thermodynamics is not concerned about how and at what rate chemical reactions are carried out, but is based on initial and final states of a system undergoing the change.

Discussion

1694.	The specific heat capacities of three metals are given below. If 1.00g of each metal is heated to `100^(@)C` and added to `10.0g` of `H_(2)O` at `25.0^(@)C`, what is the order of the temperatures of the final mixtures form the lowest to the highest?A. `FeltZnltPb`B. `PbltZnltFe`C. `ZnltPbltFe`D. `ZnltFeltPb`
Answer» Correct Answer - B

Discussion

1695.	Enthalpy change when a solution is diluted from 4 M to 2 M is -1.6 KJ/mol . Enthalpy change when 5 litre of such a solution is diluted, is:A. `-1.6KJ`B. `-3.2KJ`C. `-32Kj`D. `-16KJ`
Answer» Correct Answer - c

Discussion

1696.	A mixture of hydrogen gas and theortical amount of air at `25^(@)` C and a total pressure of 1atm , is exploded in a closed right vessel . If the process ossurs under adiabatic conditions then using the given data anwer the question that follow : Given : `C_(p)(N_(2))and C_(p)(H_(2)O)"are" 8.3 and 11.3 caldeg^(-1)mol^(-1)` not necessarily in the same order. `DeltaH_(f)[H_(2)O(g)]=-57.8kcal` `["take air as" 80% N_(2),20%O_(2)"by volume".]` the value of `C_(p)of N_(2)and H_(2)O` inthe order `N_(2),H_(2)O` will be : (in cal`deg^(-1)mol^(-1)`A. 8.3,8.3B. 8.3,11.3C. 11.3,11.3D. 11.3,8.3
Answer» Correct Answer - b

Discussion

1697.	When `MgO` reacts with `H_(2)O` at `25^(@)C` and 1 atm, the volume change is `-4.6mL. mol^(-1).` `MgO(s)+H_(2)O(l)toMg(OH)_(2)(s)` What is the value of `deltaH- deltaE` for this reaction?A. `-4.7xx10^(-1)J.mol^(-1)`B. `-4.7xx10^(-2)J.mol^(-1)`C. `4.7xx10^(-2)J.mol^(-1)`D. `4.7xx10^(-1)J.mol^(-1)`
Answer» Correct Answer - A

Discussion

1698.	A mixture of hydrogen gas and theortical amount of air at `25^(@)` C and a total pressure of 1atm , is exploded in a closed right vessel . If the process ossurs under adiabatic conditions then using the given data anwer the question that follow : Given : `C_(p)(N_(2))and C_(p)(H_(2)O)"are" 8.3 and 11.3 caldeg^(-1)mol^(-1)` not necessarily in the same order. `DeltaH_(f)[H_(2)O(g)]=-57.8kcal` `["take air as "80% N_(2),20%O_(2)"by volume".]` What will be the final pressure in atm?A. `~=8.5`B. `~=7.6`C. `~=5.46`D. `~=0.85`
Answer» Correct Answer - a

Discussion

1699.	A mixture of hydrogen gas and theortical amount of air at `25^(@)` C and a total pressure of 1atm , is exploded in a closed right vessel . If the process ossurs under adiabatic conditions then using the given data anwer the question that follow : Given : `C_(p)(N_(2))and C_(p)(H_(2)O)"are" 8.3 and 11.3 caldeg^(-1)mol^(-1)` not necessarily in the same order. `DeltaH_(f)[H_(2)O(g)]=-57.8kcal` `["take air as "80% N_(2),20%O_(2)"by volume".]` What will be the maxiimum temperature attained if the process occurs in adiabatic container?A. `~=2940 K`B. `~=2665K`C. `~=1900K`D. `~=298K`
Answer» Correct Answer - a

Discussion

1700.	`H_(2)` gas is mixed with air at `25^(@)C` under a pressure of 1 atmosphere and exploded in a closed vessel. The heat of the reaction, `H_(2(g))+(1)/(2)O_(2(g))rarrH_(2)O_((v))` at constant volume, `DeltaU_("298 K")=-"240.60 kJ mol"^(-1)` and `C_(V)` values for `GH_(2)O` vapour and `N_(2)` in the temperature range `"298 K and 3200 K are 39.06 JK"^(-1)"mol"^(-1) and "26.40 JK"^(-1)"mol"^(-1)` respectively. The explosion temperature under adiabatic conditions is (Given : `n_(N_(2))=2)`A. 2900 KB. `2900^(@)C`C. 2917 KD. `3000^(@)C`
Answer» Correct Answer - C If the process is carried out adiabatically and isochorically, `DeltaU=DeltaU_("heating")+DeltaU_("298 K")=0` or `DeltaY_("heating")=-DeltaU_(298K)` `=int_(298K)^(T_(f))n SigmaC_(v)dT=+240.60" kJ mol"^(-1)` `SigmanC_(v)=n.C_(v(H_(2)O_((v)))+nC_(v(V_(2(g))))` `=(39.06+2xx26.40)=91.86JK^(-1)mol^(-1)` by using the value of `SigmanC_(v)` in the above equation `(91.86)(T_(f)-298)=240600"J mol"^(-1)` `T_(f)-298=(240600)/(91.86)=2619K` `T_(f)=2619+298=2917K`

Discussion

Explore topic-wise InterviewSolutions in .

Gas with in a chamber, passes through the cycle shown in (figure). Determine the net heat added to the system during process AB is `Q_(AB)= 20J`. No heat is transferred during process BC and net work done during the cycle is `15J`

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

Predict in which of the following, entropy increases:A. A liquid crystallizes into a solid.B. Temperature of a crystalline solid raised from 0 K to 115 K.C. `2NaHCO_(3)(s) rarr Na_(2)CO_(3)(s)+CO_(3)(g)+H_(2)O(g)`D. `H_(2)(g) rarr 2H(g)`

The gas in a refrigerator causes cooling on expansion because:A. Work done by the gas is converted into heatB. Heat of the gas is lost as work is done by the gasC. The heat is spread over a large spaceD. None of the above

A reaction proceeds through two paths I and II to convert `X rarr Z`. What is the correct relationship between `Q. Q_(1) and Q_(2)` ?A. `Q=Q_(1)xxQ_(2)`B. `Q=Q_(1)+Q_(2)`C. `Q=Q_(2)-Q_(1)`D. `Q=Q_(1)//Q_(2)`

Which of the following is the correct option for the free expansion of an ideal gas under adiabatic condition?A. `q=0, Delta T ne = 0, w = 0`B. `q ne 0, Delta T = 0, w = 0`C. `q = 0, Delta T = 0, w = 0`D. `q = 0, Delta T lt 0, w ne 0`

In an isothermal process the volume of an ideal gas is halved. One can say thatA. Internal energy of the system decreasesB. Work done by the gas is positiveC. Work done by the gas is negativeD. Internal energy of the system increases

A thermodynamic process in which temperature T of the system remains constant though other variable P and V may change, is calledA. Isochoric processB. Isothermal processC. Isobaric processD. None of these

`At298 K,DeltaH_("combustion")^(@)("sucrose")=-5737"kJ"//"mol"` and `DeltaG_("combustion")^(@)("sucrose")=-6333"kJ"//"mol."` Estimate additional non-PV work that is obtainced by raising bemperature to `310` K. Assume `Delta_(r)Cp=0` for this temperature change.

Calculate `DeltaG` (in bar-L) when a definite mass of a monoatomic ideal gas at 1 bar and `27^(@)C` is expanded adiabatically against vacuum from 10 L to 20 L (In 2=0.7).

How much heat (in kJ) should be supplied to a rigid conducting vessel of volume V litres, so that 0.5 mole of C is formed in the reaction : `A(g)+B(g)to C(g),Delta H=+7.6kJ` Take `R= 8"J"//"K mole"`, T=300 K

Which is a good fuel `CH_(4)` or `C_(2)H_(6)` ? The standard enthalpy of formation of`CH_(4),C_(2)H_(6),CO_(2)` and `H_(2)O` are -74.8, -84.6, -393.5 and -286kJ `mol^(-1)` respectively .

Calculate the enthalpy changewhen 2.38 g of carbonmonoxide ( CO) vaporize at its normal boiling point. Given that the enthalpy of vaporisation of carbon monoxide is6.04 kJ `mol^(-1)` at its normal boiling point of `82.0` K.

One mole of ideal gas expands freelt at 310 K from five litre volume to 10 litre volume. Then `Delta E` and `Delta H` of the process are respectivelyA. 0 and 5 calB. 0 and `5xx300` calC. 0 and 0D. 5 and 0 cal

Red phosphorus reacts with liquid bromine in an exothermic reaction `2P(s) + 3 Br_(2) (l) rarr PBr_(3) (g), Delta_(r) H^(@) = - 243 kJ mol^(-1)` Calculated the enthalpy change when `2.63 g` of phosphorus reacts with an excess of bromine in this way.A. `10.3 kJ`B. `1536 kJ`C. `7.5 kJ`D. `20.3 kJ`

Define thermal efficiency of a heat engine.

In a cyclic process, the area enclosed by the loop in the P – V plane corresponds to (A) ∆U (B) W(C) Q – W (D) W – Q.

The efficiency of a heat engine is given by η = (A) QH /W (B) W/QC (C) W/QH(D) QC /W.

In a cyclic process, (A) ∆U = Q (B) Q = 0 (C) W = 0 (D) W = Q

In an isobaric process, in the usual notation, (A) W = P (Vf – Vi) (B) W = Q (C) W = – ∆U (D) ∆T = 0.

In an adiabatic process, in the usual notation, W =(A) \(\frac{P_iV_i-P_fV_f}{\gamma-1}\)(B) \(\frac{nR∆T}\gamma\)(C) nR\(\gamma\)(Ti - Tf)(D) \(\frac{P_iV_i-P_fV_f}{\gamma}\)

In an adiabatic process, in the usual notation, (A) TVγ = constant (B) PTγ = constant (C) W = 0 (D) PVγ = constant.

In an adiabatic process, in the usual notation, (A) ∆ P = 0 (B) ∆ V = 0 (C) Q = 0 (D) ∆U = 0.

In an isobaric process, in the usual notation, (A) W = nCv (Tf – Ti) (B) Q = nCp (Tf – Ti) (C) ∆U = nR (Tf – Ti) (D) W = 0.

In the usual notation, the isothermal work, W = (A) P(Vf – Vi) (B) nRT(Pi/ Pf) (C) nRT ln(Pi/Pf) (D) nRT(Pf/Pi).

In an isothermal process, in the usual notation, (A) W = nRT (V /V ) (B) W = ∆ U (C) W = Q (D) W = 0.

In an isothermal process, in the usual notation, (A) W = P(Vf – Vi)(B) W = 0 (C) W = V(Pf – Pi) (D) W = nRT In(Vf/Vi).

In an isothermal process, in the usual notation, (A) PV = constant(B) V/T = constant (C) P/T = constant (D) Q = 0.

According to the first law of thermodynamics, in the usual notation, (A) Q = ∆U + W (B) Q = ∆U – W (C) Q = W – ∆U (D) Q= -(∆ U + W).

In isothermic process, which statement is wrongA. Temperature is constantB. Internal energy is constanC. No exchange of energyD. (a) and (b) are correct

Explain heat of neutralisation with an example.

For is process involiving solids `and//or` liquids,A. `Delta H gt Delta U`B. `Delta H lt Delta U`C. `Delta H = Delta U = 0`D. `Delta H ~= Delta U`

Knowing the viscosity coefficient of helium under standard conditions, calculate the effective diameter of the helium atom.

Thermodynamics is not concerned about ________.A. energy changes involved in a chemical reactionB. the extent to which a chemical reaction proceedsC. the rate at which a reaction proceedsD. the feasibility of a chemical reaction

Enthalpy change when a solution is diluted from 4 M to 2 M is -1.6 KJ/mol . Enthalpy change when 5 litre of such a solution is diluted, is:A. `-1.6KJ`B. `-3.2KJ`C. `-32Kj`D. `-16KJ`

When `MgO` reacts with `H_(2)O` at `25^(@)C` and 1 atm, the volume change is `-4.6mL. mol^(-1).` `MgO(s)+H_(2)O(l)toMg(OH)_(2)(s)` What is the value of `deltaH- deltaE` for this reaction?A. `-4.7xx10^(-1)J.mol^(-1)`B. `-4.7xx10^(-2)J.mol^(-1)`C. `4.7xx10^(-2)J.mol^(-1)`D. `4.7xx10^(-1)J.mol^(-1)`