Energetics Questions and Answers

1 mole of methanol when burnt in oxygen gives out 723 kJ mol heat If 1 mole of oxygen i used what will be the amount of heat evolved 2 964 kJ 1 723 kJ Ans 3 3 482 kJ 4 241 kJ

35 Ammonium chloride when dissolved in water leads to cooling sensation The dissolution of NH Cl at constant temperature is accompanied by 1 Increase in entropy 2 Decrease in entropy 3 No change in entropy 4 No change in enthalpy

A rigid container contain 1 Kg m N gas at 400 K if final temprature is 800 K then find change in entropy kJ K Given C 29 099 joule to doidW P OHO HD di 1 512 86 joule pitan 2 1025 736 joule 3 256 43 joule 4 170 9 joule

An ideal gas at temperature T and initial volume V is first expanded adiabatically to a volume 2V and then isothermally expanded to volume V It is now compressed adiabatically until its temperature becomes T again The final volume is 1 V 2

35 If a ground water contains H S at concentration of 2 mg l determine the pressure of H S in head space of a closed tank containing the ground water at 20 C Given that for H S Henry s constant is equal to 6 8 x 10 bar at 20 C Bark 36 sd har stor ei noitulo or to see C 553 Paibiloa asl D 55 10 Pa X A 720 Pa B 77 10 Paio A pressure cooker reduces cooking time for food because oz zalupsion

at would be the heat released in calorie when 200 cm of 0 1 M H SO4 is mixed 175 cm of 0 2 M KOH

In an irreversible process taking place at constant T and P and in which only pressure volume work is being done the change in Gibb s free energy dG and change in entropy Prouler sils ds satisfy the criteria 24 bi 0163 E T P V E T P a ds 0 dG p 0 b ds 0 dG p 0 d ds 0 dG p 0 V E c ds 0 dG p 0 TP

1 Calculate the C H bond energy in methane at 25 C from the data Heat of formation of methane is 17 9 kcal heat of sublimation of carbon is 171 1 cal and heat of formation of hydrogen atoms is 52 1 kcal mol 700 and 393 5 kcal

Calculate the maximum temperature for the following reaction carried out under adiabatic conditon at constant pressure Assume O g is present in stoichiometric amount Given CH g 20 g CO g 2H O 4H 890 kJ mol AHO vap H O 45 kJ mol CPM CH g 35 J k mol CPM CO g 36 J k mol CPM H O g 32 J k mol all data provided at 298 K B 7702 K C 8298 K A 308 K D None of these

d C In C In T T 4TT 2 Wildcom 70 Assuming ideal gas behaviour the AS for the isothermal mixing of 0 8 mole N and 0 2 mole of O is In 2 0 7 In 10 2 3 a 0 96 cal K b 0 32 cal K c 0 96 cal K d 0 32 cal K 6 If all the following gases are in monoatomic form which has great

39 The AH N O5 g in kJ mol on the bases of the following data is AH 114 kJ mol AH 102 6 kJ mol 1 15 1 2NO g O g 2NO g 4NO g O g 2N O5 g A H NO g 90 2 kJ mol 2 30 2 3 36 2 4 none of these

Rate of which reactions increases with temperature 1 Of any reaction 2 Of exothermic reaction 3 Of endothermic reaction 4 Of None

2 For a given reaction AH 35 5 kJ mol and AS 83 6 J K mol The reaction is spontaneous at Assume that AH and AS do not vary with temperature T 425 K c T 298 K b all temperatures d T 425 K NEFT 2017

26 Among the following the state function s is are 2009 a internal energy b irreversible expansion work c reversible expansion work d molar enthalpy

The bond dissociation enthalpies of H g and N g are 435 95 kJ mol and 941 8 kJ mol and enthalpy of 46 024 kJ mol 1 What is the formation of NH3 g is enthalpy of atomization of NH3 g a 0 170 MJ mol 1 c 1 170 MJ mol 1 b 1 70 MJ mol 1 d 2 130 MJ mol 1 faitric acid th

For the hypothetical reaction A g B g 2AB g A G and A S are 20 kJ mol and 20 JK mol respectively at 200 K If A Cp is 20 JK mol then A H at 400 K is a 20 kJ mol b 7 98 kJ mol c 28 kJ mol Revisie d None of these

In 1 L saturated solution of AgCIIK AgCl 1 6 x 10 01 0 1 mole of CUCI K CUCI 1 0 x 10 is added The resultant concentration of Ag in the solution is 1 6 x 10 The value of x is A 9 B 5 C 7 D 8

34 For the decomposition reaction NH COONH4 s 2NH3 g CO g the K Kp 2 9x105 atm The total pressure of gases at equilibrium when 1 0 mol of NH COONH 5 was taken to start with would be

A stationary mass of gas is compressed without friction from an initial state of 0 3 m and 0 105 M Pa to a final state of 0 15 m and 0 105 M Pa The pressure remaining constant During the process there is a transfer of 37 6 kJ of heat from the system During the process the amount of internal energy change is a 28 85 kJ c 21 85 MJ b 21 85 kJ d 53 35 kJ

23 The reversible expansion ob an ideal gas under adiabatic and isothermal conditions is shown in the figure Which of the following statement s is are correct 2012 Const a T 1 b T T c W P 0 V T isothermal W Isothermal Adiabatic adiabatic V P2 V2 T2 03 V3 T3

For gas A in a calorimeter heat evolved is 250 kJ mol For 0 2 mol of A temperature rise from 298 K to 300 K Find out heat capacity of calorimeter 1 12 5 kJ K 3 50 kJ K 2 25 kJ K 4 100 kJ K

In the reactions 1 H 2H H 1 0 20 H O III 2H O 11 AH 436 kJ AH 241 81 kJ 0 H O AH 2 H O can be formed either by II or III Ratio of enthalpy change in III to II is 1 2 8 2 0 36 3 1 2 4 0 82

Which has the highest entropy per mol of the substance 1 H at 25 C and 1 atm 2 H at STP 3 H at 100 K and 1 atm 4 H at 0 K and 1 atm

A its size B The magnitude of It s C The sign of the charge alone D Both magnitude and sign of its charge 42 A one litre vessel containing a gas at 27 C 6g of charcoal was introduced into it The pressure of the gas fall down from 700 mm to 400 mm Calculate the volume of the gas STP adsorbed per gm of charcoal density of charcoal 1 5 g cm A 50 5 g B 59 6 g C 62 3 g 43 Decomposition of H O can be prevented in presence of D 72 g

8 2Zn O 2ZnO AG 616 J 2Zn S 2ZnS AG 293 J S 202 2SO2 AG 408 J AG for the following reaction 2ZnS 30 2ZnO 2SO is 1 1462 J 3 501 J 2 1317 J bohovnco 4 731 J

If LPG cylinder contains mixture of butane and isobutane then the amount of oxygen that would be required for combustion of 1 kg of it will be 1 1 8 kg 2 3 58 kg 3 2 7 kg 4 4 5 kg

One mole of a non ideal gas undergoes a change of state 2 0 atm 3 0 L 95 K 4 0 atm 5 0 L 245 K with a change in internal energy AE 30 0L atm The change in enthalpy AH of the process in L atm is 2002 3M a 40 0 b 42 0 c 44 0 d not defined at constant

2 4 A rigid container contain 1 kg N gas at 400 K if final temeprature is 800 K then find change in entropy J K Given C 29 099 joule 2 1025 736 4 170 9 1 512 86 3 256 43

3 In an isulated container water is stirred with a rod to increase the temperature Which of the following is true 1 AU W 0 q 0 3 AU 0 W q 0 2 AU W q 0 4 W 0 AU A

21 Given the bond dissociation energies below in kcal mole estimate the AH for the ary carbon e quaternary carbon propagation step CH 3 2 CH Cl2 CH 3 2 CHCl Cl A 98 CH3CH2CH2 H CH3 2 CH H Cl Cl H Cl CH3CH2CH2 Cl CH3 2 CH Cl a 30 kcal mole c 40 kcal mole CM3 CM 2 95 58 103 aniq Indic 81 80 b 22 kcal mole d 45 kcal molo 45 We ala 85

cylindrical base 7 A container 821 cm fitted with frictionless massless piston consist of five valves such as I II III IV and V The distance of valves from the initial position of piston is 15 30 40 45 and 50 cm respectively The initial height of piston from the base of container was 60 cm These valves open automatically if pressure exceeds over 1 5 2 2 2 5 4 4 and 4 8 atm respectively Under the given conditions shown in the diagram the system is in state of equilibrium The piston is now compressed moved downward slowly and isothermally Neglect the volumes of valve connectors Valve I Valve III T Valve V P 1 atm T 300 K Valve II Valve IV in the container are area a Value II will be opened first b As the piston crosses the value which will be opened first the remaining number of moles 5 3 c Value V will be the second value which open d Number of moles will be zero as the piston

The initial pressure of COCl is 1000 torr The total pressure of the system becomes 1500 torr when the equilibrium COCI g attained at constant temperature of a reaction 1 1500 3 2500 prze 2 1000 4 500 CO g Cl g is The value of K

graphite 2 g CO g AH 393 kJ mol H O H g 1 2O2 g AH 286 kJ mol C H OH 30 g 2CO g 3H O l AH 1368 kJ mole The AH of C H OH will be 1 689 kJ 3 138 kJ 2 344 5 kJ 4 276 kJ

19 Although q is a path dependent function but q is independent P of path because a AH is independent of path b U P and V are state functons and H depends on them c both a and b A d none of these 9000 b

For an ideal gas consider only P V work in going from an initial state X to the final state Z The fina 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 AS as change in entropy and w as work done P atmosphere X Z V litre a ASx z ASX y ASy Z b wx z Wx y Wy Z c WX Y Z Wx Y

A cylinder fitted with a piston contains 0 10 moles of air at room temperature 20 C The piston is pushed so slowly that the air within the cylinder remain essentially in thermal equilibrium with the surroundings The work done by the air within the O cylinder if the final volume is one half the initial volume

Latent heat of vaporisation of a liquid at 500 K and 1 atm pressure is 10 0 kCal mol What will be the change in internal energy of 3 mol of liquid at same temperature and pressure 1 13 0 kCal AV AH Ang RT 3 27 0 kCal X 3H O l 3H Ocg 2 13 0 kCal 31 n 3 4 27 0 kCal 3x10 3 X 2 3x10 g tooo Nool

The heat of combustion of CH is 2878 kJ mot If the heats of formation of CO and H 0 a 393 5 kJ moland 285 8 kJ mol then the hea of formation of CH is 1 125 0 kJ mol 2 126 75 kJ mol 4 402 3 402 5 kJ mol

Anf of 348 3 318 4 168 8 146 0 90 8 58 5 187 9 217 8 Which of the following oxide can be converted to metal easily ZnO Cu O HgO PbO 1 ZnO 3 PbO 2 HgO 4 Cu O

Heat of atomisation of NH and N H are x kcal mol and y kcal mot respectively Calculate average bond energy of N N bond 4y 3x 1 kcal mol 2 2y 3x kcal mol 3 4y 3x 4 3y 4x kcal mol 4 3 kcal mol 1

3 For the allotropic change represented by the equation C graphite C diamond the enthalpy change AH 1 9 kJ If 6 g of diamond and 6 g of graphite are separately burnt to yield CO the heat liberated in first case is a less than in the second case by 1 9 kJ Vogrine s MISTURIN b more than in second case by 11 4 kJ Insa takto pie Oct c more than in the second case by 0 95 kJ EL CURST d less than in the second case by 11 4 kJ Consbl BIA 6

The heats of combustion of hydrogen car bon monoxide and methane are 285 284 and 890 kJ mor The calorific value is maximum for a H b CO c CH d Cannot be redicted as information is incomplete

37 For the reaction X O4 l 2XO g AU 2 1 kCal AS 20 cal K 1 at 300 K Hence AG is 1 2 7 kCal 3 9 3 kCal 2 2 7 kCal 4 9 3 kCal

2 moles of an ideal monoatomic gas undergoes reversible expansion from 4 L 400 K to 8 L such that TV2 constant The change in enthalpy of the gas is b 3000R d 3000R a 1500R c 1500R

The heat of atomization of methane and ethane are 360 kJ mol and 620 kJ mol respectively The longest wavelength of light capable of breaking the C C bond is Avogadro number 6 02 x 1023 h 6 62 10 34 J s 1 49 103 nm 1 2 3 4 2 48 103 nm 2 48 104 nm 1 49 x 104

1 1 182 2 0 182 3 0 818 26 For the reaction A g B g C g D g AHO and ASO are respectively 29 8 kJ mol 1 and 0 100 kJ K 1 mol 1 at 298K The equilibrium constant for the reaction at 298K is JEE Main Online 20161 1 1 0 x 10 10 3 1 0 x 1010 2 10 4 1 nposition to form a mixture of gases

133 Which of the following thermodynamic conditions at constant pressure and temperature is necessary for the spontaneity of a process live en is oldierstommad a d U TS PV 0 d U TS PV 0 e b d U TS PV 0 d d TS PV 0

The pressure in a bulb dropped from 2000 to 1500 mm of Hg in 47 min when the contained oxygen leaked through a small hole The bulb was then evacuated A mixture of oxygen and another gas of molar mass 79 in the molar ratio of 1 1 at a total pressure of 4000 mm of Hg was introduced Find the molar ratio of two gases remaining in IIT 81 the bulb after a period of 75 min

c In the reactions where enthalpy value determination is difficult by experiments the enthalpy value can be calculated by a Kirchoff s equation b Hess s law ROT c Henry s law d van t Hoff law ai norism to 10 baste sil

D 3 1 the synthesis ciation of HI D 0 02 s 81 When NaNO is heated in a closed vessel O is liberated and NaNO is left behind At equilibrium A addition of NaNO favours reverse reaction B addition of NaNO favours forward reaction C increasing temperature favours forward reaction D increasing pressure favours forward reaction