Energetics Questions and Answers

7 For the reaction 298 K 24 B C AH 100 kcal and AS 0 050 kcal K If AH and AS are assumed to be constant over the temperature range above what temperature will the reaction become spontaneous 1 1000 K 2 1500 K 3 2000 K 4 2500 K

30 For given following equations and AH values determine 90 the enthalpy of reaction at 298 K for the reaction C H g 6F g 2CF g 4HF g H g F g 2HF g AH 537 kJ C s 2F g CF 9 AHS 680 kJ 2C s 2H g C H g AH 52 kJ 1 1165 2 2486 3 1165 HAFT

0 For a reaction with AH 95 kJ mol decide if the following statement is true If the statement is false choose the statement that makes it true Select the single best answer The product is favored at equilibrium Assume the entropy term is small compared to the enthalpy term O The statement is false Neither the product nor the starting material is favored at equilibrium The statement is false The equilibrium position of the reaction cannot be approximated The statement is true The statement is false The starting material is favored at equilibrium O O

5 Over small temperature ranges heat capacities are often treated as if they were constant though they are not Over the range of 300 to 6000 K the constant pressure heat capacity for nitrogen gas can be modelled as CP m a bT cT dT e T a J K mol 26 09200 b J K mol 8 218801 x 10 3 c J K mol 1 976141 x 10 6 d J K4 mol 0 159274 x 10 How much heat is needed to heat three moles of N gas from 300 to 800 K e J K mol 0 044434 x 106 10 q 100 kJ

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

The enthalpy of formation of CH g H O l and CO g are 74 8 kJ mol 285 5 kJ mol and 393 5 kJ mol respectively Then the standard enthalpy of combustion of CH g is a 890 3 kJ mol c 604 5 kJ mol b 604 5 kJ mol d 890 3 kJ mol

270 Given C s O2 g CO2 AH 94 2 K Cal H g 1 2O2 g H OAH 68 3 K Cal CH4 8 202 g CO2 g 2H O AH 210 8 K Cal what will be heat of formation of CH in K Cal 1 45 9 2 20 0 3 47 8 4

When the formation of one mole HBr g takes place reversibely from gaseous H and liq Br2 at 300K and 1 atm increase in entropy of the surrounding is 170 J K What is change in entropy J K of the system if reaction 2HBr g H g Br2 1 is carried out reversibly at 300K in rigid container Given R 8 3 J mol K

The equilibrium constants of a reaction at 298 K and 308 K are 1 0 10 and 2 x 10 respectively the reaction is a Exothermic b Endothermic c May be endothermic or exothermic d Cannot be predicted

What will be the enthalpy of combustion of carbon to produce carbon monoxide on the basis of data given below C s O2 g CO2 g 393 4 kJ CO g 2O2 g CO2 g 283 0 kJ Question Type Single Correct Type 1 2 676 4 kJ 676 4 kJ

Freezing point lowering expression is AT Km molality Which of the following assumptions are considered for the validity of above equation A The solution is dilute B The AH latent heat of fusion of solvent is independent of temperature between the actual and normal freezing point C The solid phase consists of pure solvent when solution is allowed to cool D AT is not equal to 3K for 3 mol L solution

Choose the incorrect statement A The molar free energies of two phases of the same single substance in equilibrium with another at a given P and T are equal B At the boiling point of liquid entropy of vaporisation is the enthalpy of vaporisation per degree absolute temperature C In an endothermic reaction entropy of the universe increases D AUVs 0 at equilibrium

Lattice enthalpy of nacl is 788 kj mol and hydration enthalpy of nacl is 784 kj mol Now solution of enthalpy is 4 kj mol Then how I can identify bond of nacl may be dissociated or non dissociated 10 01 RM

d Ca 12 An electron that has the quantum number n 3 and dm 2 a must have spin value 1 2 b must have 1 1 c must have l 0 1 or 2 must have 1 2 5 The funda l nton 21 1912

Match List I with List II and select the correct answer using the codes given below the lists List I G P G A B C D T P H T A F a 5 b 5 c 3 P H D B C 1 2 4 3 2 4 5 2 1 List II 1 MJT 2 T 3 S 4 P 5 V 2010

EER INSTITUTE Atomic REThe heat of combustion of solid benzoic acid at constant 52 27 C Busch 3 olume is 321 30 kJ at 27 C The heat of combustion at 321 30 constant pressure is 1 321 30 300 R 2 321 30 300 R 3 321 30 450 R 4 321 30 150 R 2 321 30 300 R 321 30 7X RX B 1 321 30 300 R 3 321 30 450 R AH AEtang RT op cr R 8 3 321 3 8 3 4 321 30 150 R 53 FA St He cada que33

46 A Decrease of free energy during the process under 146 A fer a la constant temperature and pressure provides a measure of 11 T PQ its spontaneity R A spontaneous change must have ve sign of AS system AS trupo2 R Uchad fa system Tas block and 14 4

Calculate the enthalpy change accompanying the freezing of 1 00 mol water at 10 0 C to ice at 10 0 C AH 1 435 kcal mol at 0 C O 1 435 kcal mol 1 343 kcal mol O O 1 343 kcal mol 1 435 kcal mol

11 In isothermal free expansion of an ideal gas NCERT Pg 1667 1 AH 0 2 AU 0 3 AW 0 4 All of these 12 Intensive property among the following

For the reaction of one mole of zinc dust with one mole of sulphuric acid in a bomb calorimeter AU and w correspond to a AU 0 w 0 c AU 0 w 0 b AU 0 w 0 d AU 0 w 0 2005 2015

51 Which of the following expressions is true 1 1 A H CO 9 4 H CO 9 2 4 H CO g 4 H C graphite 4 H 0 9 1 3 A H CO g A H CO 9 4 H 0 9 2 4 AFHO CO g A combH C graphite Acomb H CO g 41 51 f Ah Het H10 W 90 which 2 1 K 2 Nie 1 AH CO 9 4 H CO 2 9 CH02 3 Bot 4 No 2 AH CO g A H C graphite 4 H which 1 Hig 2 3 A H CO 9 A H CO 9 A H H 3 ox 4 A H CO g A combH C graphite AcombH 4 A 1

Atomic Structure Chemical Arithmetics Solution Thermodynamics fe aliquise alegien gravfer Fe O s 3 H g 2 Fe s 3H O AHO 35 kJ 1 af fag f AHD 26 KJ TITUTE 65 For reduction of ferric oxide by hydrogen Fe O s 3 65 H g 2 Fe s 3H O AHO 300 35 kJ The reaction was found to be too exothermic To be convenient it is desirable that AHO should be at the most 26 kJ At what temperature is it possible C Fe O3 105 C Fe s 25 C H O 75 C H 9 29 all are in J mol 1 480 43 K 2 508 43 K 3 580 43 K 4 408 43 K plo of an idal gas A C 3R and 2 mole of an ideal 66 C3R 1 mole s 300 C Fe 0 105 C Fe s 25 CH O 0 75 CH Q 29 J mol 1 480 43 K 2 508 43 K 3 580 43 K 4 408 43 K

8 For a given reaction energy of activation for forward E is 80 kJmol 1 reaction AH 40 kJmol 1 for the reaction A catalyst lowers E by 20 kJ mol 1 The ratio of energy of activation for reverse reaction before and after addition of catalyst is 1 1 0 Quin 2 0 5 prib1000A 3 1 2 tspol att bido 4 2 0 nitido ad

C3H8 5 020 When this reaction is considered for thermodynamic studies what is the partial pressure of oxygen gas in the standard mixture state a 0 2500 atm b 0 304 atm c 1 000 atm d 7 000 atm correct answer

We may now formulate another postulate n an isolated system there is always a endency for the systems energy to become nore disordered or chaotic and this could be criterion for spontaneous change

1 mole of an ideal gas y 1 5 taken through a series of processes as shown in following in P V curve Adiabatic C WAR 600 cal AB D WBC 300 In2 cal D B Isothermal C Information I The temperature at state A is 300 K Information II The reversible isothermal expansion form B to C doubles the volume Information III The entropy change of the system from C to D is 4 n16 cal K Select the correct option s using the above information A The entropy change of the system from D to A is 3R In8 B The temperature at point D is 2400 K

59 The enthalpy changes at 298 K in successive breaking of O H bonds of water are H O H g OH g A H 498 kJ mol OH g H g O g AH 428 kJmol the bond enthalpy of O H bond is 1 498 kJ mol 2 428 kJ mol 3 70 kJ mol 4 463 kJ mol e

8 When a certain process is carried out at in a sealed rigid container the heat flow is 50 6 joules When the same process is carried out at a constant pressure of 1 25 atm the heat flow is 72 2 joules What is the value of AH at constant volume process a 21 6 J b 72 2 J c 72 2 J d 21 6 J correct answer

Calculate the of radiant energy converted into kinetic energy of x atoms x atom forms afte dissociation of X molecules by the absorption of 5 quantum of radiation having wave lengt 5000 A If bond energy of X molecules is 250 KJ mol

Consider the following spontaneous reaction 3X g 2X3 g What are the sign of AH AS and AG for the reaction SUF AUFT 1 ve ve ve 2 ve ve ve 3 ve ve ve 4 ve Ave ve 16 3 3X g 2X3 9 AH AS AG fara at 83 1 ve ve ve 2 ve ve ve 3 ve ve ve 4 ve ve ve 8 1 to 3 m 2 3 DS

57 Bond dissociation enthalphies of H g and N g are 436 0 kJ mol and 941 8 kJ mol respectively and enthalpy of formation of NH3 g is 46 kJ mol What is enthalpy of atomization of NH g 1 390 3 kJ mol 3 590 kJ mol 2 1170 9 kJ mol 4 720 kJ mol

73 Given NO g O g NO g O g AH 198 9 kJ mol O g 3 2 0 g AH 142 3 kJ mol O g 20 g AH 495 0 kJ mol The enthalpy change AH for the following reaction is NO g 0 g NO g a 304 1 kJ mol b 304 1 kJ mol c 403 1 kJ mol d 403 1 kJ mol

The standard enthalphy of formation of NH3 is 46 0 kJ mol 1 If the enthalpy of formation of H from its atoms is 436 kJ mol 1 and that of N is 712kJ mol 1 the average bond enthalpy of N H bond in NH3 is 1 1102 kJ mol 1 2 964 kJ mol 1 3 352 kJ mol 1 4 1056 kJ mol 1

Determine enthalpy of formation for H O 1 using listed enthalpies of reaction N H 1 2H O 1 N g 4H O 1 A H 818kJ mol N H 1 O g N g 2H O 1 AH 622kJ mol H g 1 20 g H O 1 AH 285 kJ mol A 383 kJ mol B 187 kJ mol C 498 kJ mol D None of these

The efficiency of an ideal gas with adiabatic exponent y for the shown cyclic process would be a y 1 2 In 2 1 1 y 1 2ln 2 21n 2 1 y 1 y 1 2ln 2 1 Vo 2V0 b d B A 2T T y 1 1 21n 2 y 1 2 In 2 1 2ln 2 1 Y Y 1

4 both magnitude and sign of charge 3 The equilibrium constant for A g B g Structure of AB is like H O If bond energy of B bond is 200 kJ mol and that of B B bond is 100 kJ mol the find ASO of above reaction 1 0 53 J mol K A Bg AB 2 d 2 536 J mol K gr 3 550 J mol K 4 5 36 J mol K Alloy is 3 AB g K 100 at 522 Koferi 100 Pep 4 522 K 3 A g B g den ende fa ata 3 100 kJ mol 3 for Kp 100 AB A B200 kJ mol B B 1 0 53 J mol K 2 536 J mol K 3 550 J mol K 4 5 36 J mol K AB g T 522 K p 100 e gro

KJ T too 317 d g 1 AB LCD 3 BC ve Potential o energy ve 4 Both AB and CD C 1 U BC AB le 85 F 1 A 2 3 4

Standard enthalpy of neutralization for strong acid HCI and weak acid HCN with strong base NaOH is given as follows HCI NaOH NaCl H O AH 57 1 kJ mole AH 51 1 kJ mole Find standard heat of dissociation ionization of weak acid HCN in units HON NaOH NaCN H O kJ mole

Two moles of a monoatomic ideal gas C 1 5 R initially at 400 K in an isolated 1 0 L piston is allowed to expand against a constant pressure of a 1 0 atm till the final volume reaches to 10 L Which of the following conclusions regarding the above change s is are true 00 The final temperature of the gas is 363 K If the same process were carried out to the same final volume but under reversible conditions final temperature would have been less than 363 K In the above process the initial and final temperatures and volumes are related as A 357

75 Which is correct for following transition E E E 2 1 E3 1 E3 2 E 1 2 2 2 3 v V V 4 all of these 76 Consider three electra 2 2 3 40 1 25 2065 I 6x5 18 1071 9 75 E E E 2 1 E3 1 E3 12 21 2 3 V3 V V 4 2 0 54 0 62 3 4 2 13 1 21

Simplified absorption spectra of three complexes i ii and iii of M ion are provided below their max values are marked as A B and C respectively The correct match between the complexes and their max values is Absorption B M A max max Wavelength nm JEE Main 2020 2 September Shift II ii MF 6 n M NCS 61 6 1 i iii M NH3 61 max a A iii B i C ii R ii C 1 b A ii B i C iii d A i B ii C iii

6 Calculate heat capacity of 40 gm triatomic nonlinear gas M 20 gm mol If it is subjected to a process such that pressure exerted is directly proportional to square of volume at under normal conditions 10 C R 20 B R D

34 When lead II nitrate is heated it decomposes into lead II oxide and two gases Nitrogen dioxide gas and oxygen gas are released What is the coefficient of nitrogen dioxide upon balancing the chemical reaction A 3 B 2 C 4 D 1

6 In which of the following reactions heat is known as standard heat of formation of CO liberated 1 2CO g O2 g 2CO2 g 0 2 8 2 C diamond 135 6 kcals CO 94 5 kcals 2 g 3 C graphite 2 g 0 CO 2 8 4 CH 202 g 2CO2 g 2H O 1 2128 kcals 94 05 kcals

A sample contain only hydrog minimum number of atoms required if total seven lines are observed in emmission spe Electron in a single electron species having atomic number Z make a transition from 2 to 1 The emitted photon 2n 3n 6Z Given 5 is absorbed by excited electron of Li in n orbit and further excite to n orbit The energy of atom is 13 6 Z n eV atom in nth orbit e following statements and identify how many statements are correct

Which of the following statements is correct for the spontaneous adsorption of a gas Question Type Single Correct Type 1 AS is negative and therefore AH should be highly positive 2 AS is negative and therefore AH should be highly negative 3 AS is positive and therefore AH should be negative AS is positive and therefore AH should also 4

false for following itement CaCO aragonite For the reaction CaCO3 Calcite given A G298 Calcite 1128 8 then Calcite form is more stable at standard conditions For the reaction kJ mol A G298 aragonite 1127 75 kJ mol C diamond 2H g CH g AH C g 4H g CH g AH a b then more heat is evolved in reaction b AH L g AH 1 s at 25 C For the exothermic reaction 2Ag s 1 2O g FTTT B TTFT C TFTT 2Ag O s at 298 K AH AU D TTTT

Two flasks A and B have equal volumes The molecules in flask A are moving two times faster than the molecules in flask B The number of molecules in flask A is eight times the number of molecules in flask B Which of the following is true about the number of collisions with the walls a The number of collisions with the walls in flask A is four times that in flask B b The number of collisions with the walls in flask B is four times that in flask A c The number of collisions with the walls in flask A is 16 times that in flask B d The number of collisions with the walls in flask B is 16

Calculate the enthalpy of formation of cane sugar C12H22011 5650 kJmor 390 kJmol 1 290 kJmol Given AcHGHz2011 ACH C ACHH 300 kJ mol 1 O 670 kJ mol 1 O 1280 kJ mol 1 O 2220 kJ mol 1

1 In the Hall process aluminium is produced by the electrolysis of molten Al O3 by the following reactions How many second would it take to produce enough aluminum by the Hall process to make a case of 24 cans of aluminium soft drink if each can uses 5 0 g of Al a current of 9650 amp is employed and the current efficiency of the cell is 90 0 1 203 2 2 148 14 3 333 4 6 17 2 Contact Number 9667591930 8527521718 0 066 1 1 230 V 2 0 858 V 3 0 80 V 4 0 8274 V 5 A fuel cell develops an electrical potential from the combustion of butane at 1 bar and 298 K C4H10 g 6 502 g 4 CO2 g 5H O 1 What is E of a cell 1 4 74 V 2 0 547 V 3 4 37 V 4 1 09 V The electrolysis of acetate solution produces ethane according to reaction 2 CH3COOC H6 g 2 CO g 2e 6 The current efficiency of the process is 80 What volume of gases would be produced at 27 C and 740 torr if the current of 0 5 amp is passed through the solution for 96 45 min 1 6 0 L 2 0 60 L 3 1 365 L 4 0 91 L 2 303 RT F For cell reaction 2H g O g 2H O 1 A S298 0 32 kJ K What is the value of AH 8 H O 1 298 Given O2 g 4H aq 4e2H O 1 E 1 23 V 1 285 07 kJ mol 2 570 14 kJ mol 3 285 07 kJ mol 4 None of these 3 100 mL of 0 05 M CuSO4 aq solution was electrolyzed using inert electrodes by passing current till the pH of the resulting solution was 2 The solution after electrolysis was neutralized and then treated with excess KI and 7 formed 1 titrated with 0 04 M Na2S O3 The standard reduction potential of normal calomel electrode and reduction potential of saturated calomel electrodes are 0 27 and 0 33 volt respectively What is the concentration of CI in saturated solution of KCI Calculate the required volume in mL of Na S O3 1 112 5 mL 2 100 mL 3 125 mL 4 None of these 4 reaction 8 If the equilibrium constant for the H aq OH aq H O 1 is 10 3 at certain temperature then what is the E for the reaction 2H O 1 2e H g 2OH aq Given 1 0 1 M 2 0 01 M 3 0 001 M 4 None Copper reduces NO into NO and NO depending upon concentration of HNO3 in solution Assuming Cu 0 1 M and PNo PNO 10 bar At which concentration of HNO3 thermodynamic tendency