__Critical compressibility factor for all substances__

Vary as square of the absolute temperature

Are more or less constant (vary from 0.2 to 0.3)

Vary as square of the absolute temperature

Vary as square of the absolute pressure

__The equation DU = Tds - PdV is applicable to infinitesimal changes occuring in__

An open system of constant composition

A closed system of constant composition

An open system with changes in composition

A closed system with changes in composition

__In the ammonia synthesis reaction, N‚Äö√á√á + 3H‚Äö√á√á ‚Äö√°√£ 2NH‚Äö√á√â + 22.4 kcal, the formation of NH‚Äö√á√â will be favoured by__

Both low temperature and high pressure

__Pick out the wrong statement:__

Entropy change for a reversible adiabatic process is zero

The expansion of a gas in vacuum is an irreversible process

An isometric process is a constant pressure process

Entropy change for a reversible adiabatic process is zero

Free energy change for a spontaneous process is negative

_On opening the door of an operating refrigerator kept in a closed room, the temperature of the room will$?

Increase in summer and will decrease in winter

_Activity co-efficient is a measure of the$?

Departure of gas phase from idea] gas law

Departure from ideal solution behaviour

Departure of gas phase from idea] gas law

_The efficiency of a Carnot heat engine operating between absolute temperatures T‚Äö√á√Ö and T‚Äö√á√á (when, T‚Äö√á√Ö > T‚Äö√á√á) is given by (T‚Äö√á√Ö - T‚Äö√á√á)/T‚Äö√á√Ö. The co-efficient of performance (C.O.P.) of a Carnot heat pump operating between T‚Äö√á√Ö and T‚Äö√á√á is given by$?

T‚Äö√á√á/(T‚Äö√á√Ö-T‚Äö√á√á)

T‚Äö√á√Ö/(T‚Äö√á√Ö-T‚Äö√á√á)

T‚Äö√á√á/(T‚Äö√á√Ö-T‚Äö√á√á)

T‚Äö√á√Ö/T‚Äö√á√á

_The expression for entropy change given by, ≈í√ÆS = - nR ln (P‚Äö√á√á/P‚Äö√á√Ö), holds good for$?

Reversible isothermal volume change

_Which of the following is not a reversible process ?$?

Expansion of an ideal gas against constant pressure

Atmospheric pressure vaporisation of water at 100¬¨‚àûC

Solution of NaCl in water at 50¬¨‚àûC

_Which is an example of closed system?$?

Lquid cooling system of an automobile

_In which of the following reaction equilibria, the value of equilibrium constant Kp will be more than is Kc?$?

2SO‚Äö√á√á + O‚Äö√á√á ‚Äö√°√£ 2SO‚Äö√á√â

2HI ‚Äö√°√£ H‚Äö√á√á + I‚Äö√á√á

N‚Äö√á√áO‚Äö√á√ë ‚Äö√°√£ 2NO‚Äö√á√á

2SO‚Äö√á√á + O‚Äö√á√á ‚Äö√°√£ 2SO‚Äö√á√â

_The compressibility factor of a gas is given by (where, V‚Äö√á√Ö = actual volume of the gas V‚Äö√á√á = gas volume predicted by ideal gas law )$?

V‚Äö√á√á/V‚Äö√á√Ö

V‚Äö√á√Ö/V‚Äö√á√á

V‚Äö√á√á/V‚Äö√á√Ö

V‚Äö√á√Ö-V‚Äö√á√á

V‚Äö√á√Ö.V‚Äö√á√á

_Compressibility factor-reduced pressure plot on reduced co-ordinates facilitates$?

Use of only one graph for all gases

_Co-efficient of performance for a reversed Carnot cycle working between temperatures T‚Äö√á√Ö and T‚Äö√á√á (T‚Äö√á√Ö > T‚Äö√á√á) is$?

T‚Äö√á√Ö/(T‚Äö√á√Ö - T‚Äö√á√á)

T‚Äö√á√á/(T‚Äö√á√Ö - T‚Äö√á√á)

T‚Äö√á√Ö/(T‚Äö√á√Ö - T‚Äö√á√á)

(T‚Äö√á√Ö - T‚Äö√á√á)/T‚Äö√á√Ö

(T‚Äö√á√Ö - T‚Äö√á√á)/T‚Äö√á√á

_The partial pressure of each constituent present in an alloy is __________ the total vapor pressure exerted by the alloy.$?

Either B or C; depends on the type of alloy

_High pressure steam is expanded adiabati-cally and reversibly through a well insulated turbine, which produces some shaft work. If the enthalpy change and entropy change across the turbine are represented by ≈í√ÆH and ≈í√ÆS respectively for this process:$?

≈í√Æ H ‚Äö√¢‚Ä 0 and ≈í√ÆS ‚Äö√¢‚Ä 0

≈í√Æ H = 0 and ≈í√ÆS = 0

≈í√Æ H ‚Äö√¢‚Ä 0 and ≈í√ÆS = 0

≈í√Æ H ‚Äö√¢‚Ä 0 and ≈í√ÆS ‚Äö√¢‚Ä 0

≈í√Æ H = 0 and ≈í√ÆS ‚Äö√¢‚Ä 0

_As the time is passing, entropy of the universe$?

Data insufficient, can't be predicted

_Which one is true for a throttling process?$?

The inversion temperature is same for all gases

A gas may have more than one inversion temperatures

The inversion temperature is different for different gases

The inversion temperature is same for all gases

The inversion temperature is the temperature at which Joule-Thomson co-efficient is infinity

_The third law of thermodynamics states that the$?

Heat transfer from low temperature to high temperature source is not possible without external work

Heat capacity of a crystalline solid is zero at absolute zero temperature

Heat transfer from low temperature to high temperature source is not possible without external work

Gases having same reduced properties behave similarly

_The energy of activation of exothermic reaction is$?

Very large compared to that for en-dothermic reaction

_Equilibrium constant decreases as the temperature$?

Decreases, for an exothermic reaction

Increases, for an exothermic reaction

Decreases, for an exothermic reaction

Increases, for an endothermic reaction

469 + Mcqs in Chemical Engineering Thermodynamics in Chemical Engineering Page 6 McqOptions

251.	__Critical compressibility factor for all substances__
A.	Are more or less constant (vary from 0.2 to 0.3)
B.	Vary as square of the absolute temperature
C.	Vary as square of the absolute pressure
D.	None of these
Answer» B. Vary as square of the absolute temperature

Discussion

252.	__In an irreversible process__
A.	Tds = dE - dW = 0
B.	DE - dW - Tds = 0
C.	Tds - dE + dW< 0
D.	Tds - dT + dW< 0
Answer» D. Tds - dT + dW< 0

Discussion

253.	__In a reversible process__
A.	Tds = dE + dW
B.	DE - dW = Tds
C.	DW - dE = Tds
D.	Tds - dW + dE >0
Answer» B. DE - dW = Tds

Discussion

254.	__The chemical potential for a pure substance is __________ its partial molal free energy.__
A.	More than
B.	Less than
C.	Equal to
D.	Not related to
Answer» D. Not related to

Discussion

255.	__The equation DU = Tds - PdV is applicable to infinitesimal changes occuring in__
A.	An open system of constant composition
B.	A closed system of constant composition
C.	An open system with changes in composition
D.	A closed system with changes in composition
Answer» E.

Discussion

256.	__In the ammonia synthesis reaction, N‚Äö√á√á + 3H‚Äö√á√á ‚Äö√°√£ 2NH‚Äö√á√â + 22.4 kcal, the formation of NH‚Äö√á√â will be favoured by__
A.	High temperature
B.	Low pressure
C.	Low temperature only
D.	Both low temperature and high pressure
Answer» E.

Discussion

257.	__If the internal energy of an ideal gas decreases by the same amount as the work done by the system, then the__
A.	Process must be isobaric
B.	Temperature must decrease
C.	Process must be adiabatic
D.	Both B and C
Answer» E.

Discussion

258.	__For an isothermal reversible compression of an ideal gas__
A.	Only ≈í√ÆE = 0
B.	Only ≈í√ÆH =0
C.	≈í√ÆE = ≈í√ÆH = 0
D.	DQ = dE
Answer» D. DQ = dE

Discussion

259.	__Water on heating from 1 to 4¬¨‚àûC__
A.	Contracts
B.	Expands
C.	Has same volume
D.	May contract or expand
Answer» B. Expands

Discussion

260.	__Work done is a__
A.	Property of the system
B.	Path function
C.	Point function
D.	State description of a system
Answer» C. Point function

Discussion

261.	__Pick out the wrong statement:__
A.	The expansion of a gas in vacuum is an irreversible process
B.	An isometric process is a constant pressure process
C.	Entropy change for a reversible adiabatic process is zero
D.	Free energy change for a spontaneous process is negative
Answer» C. Entropy change for a reversible adiabatic process is zero

Discussion

262.	__A/an __________ system is exemplified by a vessel containing a volatile liquid in contact with its vapor.__
A.	Isolated
B.	Closed
C.	Open
D.	None of these
Answer» D. None of these

Discussion

263.	__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 compounds each at 1 atm is__
A.	-2 RT ln 0.5
B.	-RT ln 0.5
C.	0.5 RT
D.	2 RT
Answer» C. 0.5 RT

Discussion

264.	_On opening the door of an operating refrigerator kept in a closed room, the temperature of the room will$?
A.	Increase
B.	Decrease
C.	Remain same
D.	Increase in summer and will decrease in winter
Answer» B. Decrease

Discussion

265.	_During a reversible isothermal expansion of an ideal gas, the entropy change is$?
A.	+ve
B.	0
C.	-ve
D.	‚Äö√ √ª
Answer» B. 0

Discussion

266.	_The principle applied in liquefaction of gases is$?
A.	Adiabatic expansion
B.	Joule-Thomson effect
C.	Both A and B
D.	Neither A nor B
Answer» D. Neither A nor B

Discussion

267.	_Activity co-efficient is a measure of the$?
A.	Departure from ideal solution behaviour
B.	Departure of gas phase from idea] gas law
C.	Vapour pressure of liquid
D.	None of these
Answer» B. Departure of gas phase from idea] gas law

Discussion

268.	_The four properties of a system viz. P, V, T, S are related by __________ equation.$?
A.	Gibbs-Duhem
B.	Gibbs-Helmholtz
C.	Maxwell's
D.	None of these
Answer» D. None of these

Discussion

269.	_With increase in compression ratio, the efficiency of the otto engine$?
A.	Increases
B.	Decreases
C.	Remains constant
D.	Increases linearly
Answer» B. Decreases

Discussion

270.	_The efficiency of a Carnot heat engine operating between absolute temperatures T‚Äö√á√Ö and T‚Äö√á√á (when, T‚Äö√á√Ö > T‚Äö√á√á) is given by (T‚Äö√á√Ö - T‚Äö√á√á)/T‚Äö√á√Ö. The co-efficient of performance (C.O.P.) of a Carnot heat pump operating between T‚Äö√á√Ö and T‚Äö√á√á is given by$?
A.	T‚Äö√á√Ö/(T‚Äö√á√Ö-T‚Äö√á√á)
B.	T‚Äö√á√á/(T‚Äö√á√Ö-T‚Äö√á√á)
C.	T‚Äö√á√Ö/T‚Äö√á√á
D.	T‚Äö√á√á/R1
Answer» B. T‚Äö√á√á/(T‚Äö√á√Ö-T‚Äö√á√á)

Discussion

271.	_Heat is added at constant pressure in an ideal __________ cycle.$?
A.	Stirling
B.	Brayton
C.	Rankine
D.	Both B and C
Answer» E.

Discussion

272.	_Gibbs free energy (F) is defined as$?
A.	F = E - TS
B.	F = H - TS
C.	F = H + TS
D.	F = E + TS
Answer» C. F = H + TS

Discussion

273.	_The expression for entropy change given by, ≈í√ÆS = - nR ln (P‚Äö√á√á/P‚Äö√á√Ö), holds good for$?
A.	Expansion of a real gas
B.	Reversible isothermal volume change
C.	Heating of an ideal gas
D.	Cooling of a real gas
Answer» C. Heating of an ideal gas

Discussion

274.	_Which of the following is not a reversible process ?$?
A.	Expansion of an ideal gas against constant pressure
B.	Atmospheric pressure vaporisation of water at 100¬¨‚àûC
C.	Solution of NaCl in water at 50¬¨‚àûC
D.	None of these
Answer» D. None of these

Discussion

275.	_Which is an example of closed system?$?
A.	Air compressor
B.	Lquid cooling system of an automobile
C.	Boiler
D.	None of these
Answer» C. Boiler

Discussion

276.	_No work is done by the system, when a reaction occurs at constant$?
A.	Volume
B.	Temperature
C.	Pressure
D.	None of these
Answer» B. Temperature

Discussion

277.	_First law of thermodynamics is mathematically stated as$?
A.	dQ = dE + dW
B.	dQ = dE - dW
C.	dE = dQ + dW
D.	dW = dQ + dE
Answer» B. dQ = dE - dW

Discussion

278.	_Trouton's ratio of __________ liquids is calculated using Kistyakowsky equation.$?
A.	Polar
B.	Non-polar
C.	Both A & B
D.	Neither A nor B
Answer» C. Both A & B

Discussion

279.	_For a thermodynamic system containing 'x' chemical species, the maximum number of phases that can co-exist at equilibrium is$?
A.	X
B.	X + 1
C.	X + 2
D.	X + 3
Answer» D. X + 3

Discussion

280.	_For an ideal gas, the chemical potential is given by$?
A.	RT dlnP
B.	R dlnP
C.	R dlnf
D.	None of these
Answer» B. R dlnP

Discussion

281.	_In which of the following reaction equilibria, the value of equilibrium constant Kp will be more than is Kc?$?
A.	2HI ‚Äö√°√£ H‚Äö√á√á + I‚Äö√á√á
B.	N‚Äö√á√áO‚Äö√á√ë ‚Äö√°√£ 2NO‚Äö√á√á
C.	2SO‚Äö√á√á + O‚Äö√á√á ‚Äö√°√£ 2SO‚Äö√á√â
D.	None of these
Answer» C. 2SO‚Äö√á√á + O‚Äö√á√á ‚Äö√°√£ 2SO‚Äö√á√â

Discussion

282.	_The compressibility factor of a gas is given by (where, V‚Äö√á√Ö = actual volume of the gas V‚Äö√á√á = gas volume predicted by ideal gas law )$?
A.	V‚Äö√á√Ö/V‚Äö√á√á
B.	V‚Äö√á√á/V‚Äö√á√Ö
C.	V‚Äö√á√Ö-V‚Äö√á√á
D.	V‚Äö√á√Ö.V‚Äö√á√á
Answer» B. V‚Äö√á√á/V‚Äö√á√Ö

Discussion

283.	_Compressibility factor-reduced pressure plot on reduced co-ordinates facilitates$?
A.	Use of only one graph for all gases
B.	Covering of wide range
C.	Easier plotting
D.	More accurate plotting
Answer» B. Covering of wide range

Discussion

284.	_Those solutions in which there is no volume change upon mixing the components in the liquid state and which, when diluted do not undergo any heat change (i.e. heat of dilution is zero), are called __________ solutions.$?
A.	Ideal
B.	Real
C.	Isotonic
D.	None of these
Answer» B. Real

Discussion

285.	_The equation, Cp - Cv = R, is true for __________ gas.$?
A.	No
B.	Any real
C.	Only ideal
D.	Both B and C
Answer» D. Both B and C

Discussion

286.	_Co-efficient of performance for a reversed Carnot cycle working between temperatures T‚Äö√á√Ö and T‚Äö√á√á (T‚Äö√á√Ö > T‚Äö√á√á) is$?
A.	T‚Äö√á√á/(T‚Äö√á√Ö - T‚Äö√á√á)
B.	T‚Äö√á√Ö/(T‚Äö√á√Ö - T‚Äö√á√á)
C.	(T‚Äö√á√Ö - T‚Äö√á√á)/T‚Äö√á√Ö
D.	(T‚Äö√á√Ö - T‚Äö√á√á)/T‚Äö√á√á
Answer» B. T‚Äö√á√Ö/(T‚Äö√á√Ö - T‚Äö√á√á)

Discussion

287.	_Sound waves propagation in air exemplifies an __________ process.$?
A.	Adiabatic
B.	Isothermal
C.	Isometric
D.	None of these
Answer» B. Isothermal

Discussion

288.	_The partial pressure of each constituent present in an alloy is __________ the total vapor pressure exerted by the alloy.$?
A.	Less than
B.	Equal to
C.	More than
D.	Either B or C; depends on the type of alloy
Answer» B. Equal to

Discussion

289.	_High pressure steam is expanded adiabati-cally and reversibly through a well insulated turbine, which produces some shaft work. If the enthalpy change and entropy change across the turbine are represented by ≈í√ÆH and ≈í√ÆS respectively for this process:$?
A.	≈í√Æ H = 0 and ≈í√ÆS = 0
B.	≈í√Æ H ‚Äö√¢‚Ä 0 and ≈í√ÆS = 0
C.	≈í√Æ H ‚Äö√¢‚Ä 0 and ≈í√ÆS ‚Äö√¢‚Ä 0
D.	≈í√Æ H = 0 and ≈í√ÆS ‚Äö√¢‚Ä 0
Answer» C. ≈í√Æ H ‚Äö√¢‚Ä 0 and ≈í√ÆS ‚Äö√¢‚Ä 0

Discussion

290.	_As the time is passing, entropy of the universe$?
A.	Is increasing
B.	Is decreasing
C.	Remains constant
D.	Data insufficient, can't be predicted
Answer» B. Is decreasing

Discussion

291.	_The internal energy of a gas obeying P (V - b) RT (where, b is a positive constant and has a constant Cv), depends upon its$?
A.	Pressure
B.	Volume
C.	Temperature
D.	All of the above
Answer» D. All of the above

Discussion

292.	_Fugacity co-efficient of a substance is the ratio of its fugacity to$?
A.	Mole fraction
B.	Activity
C.	Pressure
D.	Activity co-efficient
Answer» D. Activity co-efficient

Discussion

293.	_Internal energy is equal to the heat absorbed in case of a/an __________ process.$?
A.	Constant volume
B.	Polytropic
C.	Adiabatic
D.	Constant pressure
Answer» B. Polytropic

Discussion

294.	_Which one is true for a throttling process?$?
A.	A gas may have more than one inversion temperatures
B.	The inversion temperature is different for different gases
C.	The inversion temperature is same for all gases
D.	The inversion temperature is the temperature at which Joule-Thomson co-efficient is infinity
Answer» C. The inversion temperature is same for all gases

Discussion

295.	_The temperature at which both liquid and gas phases are identical, is called the __________ point.$?
A.	Critical
B.	Triple
C.	Freezing
D.	Boiling
Answer» B. Triple

Discussion

296.	_In the equation, PVn = constant, if the value of n = ¬¨¬± ‚Äö√ √ª, then it represents a reversible __________ process.$?
A.	Adiabatic
B.	Isometric
C.	Isentropic
D.	Isothermal
Answer» C. Isentropic

Discussion

297.	_The third law of thermodynamics states that the$?
A.	Heat capacity of a crystalline solid is zero at absolute zero temperature
B.	Heat transfer from low temperature to high temperature source is not possible without external work
C.	Gases having same reduced properties behave similarly
D.	None of these
Answer» B. Heat transfer from low temperature to high temperature source is not possible without external work

Discussion

298.	_The energy of activation of exothermic reaction is$?
A.	Zero
B.	Negative
C.	Very large compared to that for en-dothermic reaction
D.	Not possible to predict
Answer» E.

Discussion

299.	_Equilibrium constant decreases as the temperature$?
A.	Increases, for an exothermic reaction
B.	Decreases, for an exothermic reaction
C.	Increases, for an endothermic reaction
D.	None of these
Answer» B. Decreases, for an exothermic reaction

Discussion

300.	_Which of the following is an extensive property of a system?$?
A.	Heat capacity
B.	Molal heat capacity
C.	Pressure
D.	Concentration
Answer» B. Molal heat capacity

Discussion

Explore topic-wise MCQs in Chemical Engineering.

__Critical compressibility factor for all substances__

__In an irreversible process__

__In a reversible process__

__The chemical potential for a pure substance is __________ its partial molal free energy.__

__The equation DU = Tds - PdV is applicable to infinitesimal changes occuring in__

__In the ammonia synthesis reaction, N‚Äö√á√á + 3H‚Äö√á√á ‚Äö√°√£ 2NH‚Äö√á√â + 22.4 kcal, the formation of NH‚Äö√á√â will be favoured by__

__If the internal energy of an ideal gas decreases by the same amount as the work done by the system, then the__

__For an isothermal reversible compression of an ideal gas__

__Water on heating from 1 to 4¬¨‚àûC__

__Work done is a__

__Pick out the wrong statement:__

__A/an __________ system is exemplified by a vessel containing a volatile liquid in contact with its vapor.__

__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 compounds each at 1 atm is__

_On opening the door of an operating refrigerator kept in a closed room, the temperature of the room will$?

_During a reversible isothermal expansion of an ideal gas, the entropy change is$?

_The principle applied in liquefaction of gases is$?

_Activity co-efficient is a measure of the$?

_The four properties of a system viz. P, V, T, S are related by __________ equation.$?

_With increase in compression ratio, the efficiency of the otto engine$?

_Heat is added at constant pressure in an ideal __________ cycle.$?

_Gibbs free energy (F) is defined as$?

_The expression for entropy change given by, ≈í√ÆS = - nR ln (P‚Äö√á√á/P‚Äö√á√Ö), holds good for$?

_Which of the following is not a reversible process ?$?

_Which is an example of closed system?$?

_No work is done by the system, when a reaction occurs at constant$?

_First law of thermodynamics is mathematically stated as$?

_Trouton's ratio of __________ liquids is calculated using Kistyakowsky equation.$?

_For a thermodynamic system containing 'x' chemical species, the maximum number of phases that can co-exist at equilibrium is$?

_For an ideal gas, the chemical potential is given by$?

_In which of the following reaction equilibria, the value of equilibrium constant Kp will be more than is Kc?$?

_The compressibility factor of a gas is given by (where, V‚Äö√á√Ö = actual volume of the gas V‚Äö√á√á = gas volume predicted by ideal gas law )$?

_Compressibility factor-reduced pressure plot on reduced co-ordinates facilitates$?

_Those solutions in which there is no volume change upon mixing the components in the liquid state and which, when diluted do not undergo any heat change (i.e. heat of dilution is zero), are called __________ solutions.$?

_The equation, Cp - Cv = R, is true for __________ gas.$?

_Co-efficient of performance for a reversed Carnot cycle working between temperatures T‚Äö√á√Ö and T‚Äö√á√á (T‚Äö√á√Ö > T‚Äö√á√á) is$?

_Sound waves propagation in air exemplifies an __________ process.$?

_The partial pressure of each constituent present in an alloy is __________ the total vapor pressure exerted by the alloy.$?

_High pressure steam is expanded adiabati-cally and reversibly through a well insulated turbine, which produces some shaft work. If the enthalpy change and entropy change across the turbine are represented by ≈í√ÆH and ≈í√ÆS respectively for this process:$?

_As the time is passing, entropy of the universe$?

_The internal energy of a gas obeying P (V - b) RT (where, b is a positive constant and has a constant Cv), depends upon its$?

_Fugacity co-efficient of a substance is the ratio of its fugacity to$?

_Internal energy is equal to the heat absorbed in case of a/an __________ process.$?

_Which one is true for a throttling process?$?

_The temperature at which both liquid and gas phases are identical, is called the __________ point.$?

_In the equation, PVn = constant, if the value of n = ¬¨¬± ‚Äö√ √ª, then it represents a reversible __________ process.$?

_The third law of thermodynamics states that the$?

_The energy of activation of exothermic reaction is$?

_Equilibrium constant decreases as the temperature$?

_Which of the following is an extensive property of a system?$?

Critical compressibility factor for all substances

In an irreversible process

In a reversible process

The chemical potential for a pure substance is ______ its partial molal free energy.

The equation DU = Tds - PdV is applicable to infinitesimal changes occuring in

In the ammonia synthesis reaction, N‚Äö√á√á + 3H‚Äö√á√á ‚Äö√°√£ 2NH‚Äö√á√â + 22.4 kcal, the formation of NH‚Äö√á√â will be favoured by

If the internal energy of an ideal gas decreases by the same amount as the work done by the system, then the

For an isothermal reversible compression of an ideal gas

Water on heating from 1 to 4¬¨‚àûC

Work done is a

Pick out the wrong statement:

A/an ______ system is exemplified by a vessel containing a volatile liquid in contact with its vapor.

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 compounds each at 1 atm is