Energetics Questions and Answers

56 For a reaction H g 2 g 2HI g AH 37 5 kJ mol and AS 150 JK mol the temperature at which the reaction will be at equilibrium is 1 200 K 3 300 K 2 250 K 4 350 K 6 6

Q 43 The enthalpy change states for the following processes are listed below Cl g 2C1 g 242 3 kJ mol 1 g 21 g 151 kJ mol 1 ICI g I g Cl g 242 3 kJ mol 1 s 1 g 62 76 kJ mol 1 on Given that the standard states for iodine chlorine are 1 s and Cl g the standard enthalpy of formation for ICI g is 1 244 8 kJ mol 1 2 14 6 kJ mol 1 3 16 8 kJ mol 1 4 16 8 kJ mol 1

Consider the reaction B k K The rate constant for two parallel reactions were found to be 10 2 dm mole s and 4 x 10 2 dm mole s k If the corresponding energies of activation parallel reactions are 80 kJ and 100 KJ respectively then apparent net overall energy of activation of given reaction in KJ is 16 x Then x is

Question 20 The rate constant of a certain reaction is given by 212 log10 K 5 4 T A B 2929Cal C A 2712Cal D 1744Cal B C 4218Cal 2 17 log10 T Calculate the activation energy at 177 C 4

Gasoline consists of 70 heptane and 30 octane by volume The combustion of 683 76 g heptane is given according to the equation below C7 H16 1 220 2 g 7CO 2 g 8H2 O 1 Calculate the quantity of energy released if the molar enthalpy for the reaction 4464 7 kJ mol

All the sub parts are compulsory a A jacketed stirred tank with a provision for heat removal is used to mix sulfuric acid and water in a steady state flow process H SOA 1 enters at a rate of 4 at 25 C and H O 1 enters at a rate of 6 what is the rate of heat removal ind The following data are available Specific heat capacity of water 4 2 kJ kg K 1 h at kg h 10 C If the mixed stream leaves at 40 C Specific heat capacity of aqueous solution of 40 mass H SO 2 8k J kg solution K Assume the specific heat capacities to be independent of temperature Based on reference states of H SOA 1 and H O 1 at 25 C the heat of mixing for aqueous solution of 40 mass H SO4 650 kJ kg H SO

A rigid tank of 1 5 kg steel holds 0 75 kg ammonia at 800 kPa as saturated vapor The tank is now heated to 260 degrees Celcius by heat transfer Determine the amount of work and the heat transfer in the process

Tollen s test is given by aldehydes Ag e Ag Ered 0 800V C6H O6 H O CH O 2H 2e E 0 05V 12 12 7 Ox Ag NH eAg 2NH FFF RT use 38 9V Answer the following questions On adding NH pH of the solution increases to 11 then identify the effect on potential of half E increased by Ex by 0 65 V OX B E decreased by E by 0 65 V OX OX C Ered increased by Ered by 0 65 V E 0 373V red D Ered decreased by Ered by 0 65 V

Board Competitive Exa DH 48 Latent heat of fusion of ice is 0 333 kJ g The increase in entropy when 1 mole water melts at 0 C will be 1 21 98 kJ K mol 2 21 98 kcal K mol 3 21 98 JK mol 4 21 98 cal K mol The bo oint

29 29 Correct statement about heat and work is that 1 Heat appears at surface only and work in bulk 2 Heat appears in bulk and work only at surface 3 Both heat and work appear in bulk of system 4 Both heat and work appear on surface only e

One mole of O g initially at a temperature of 120 K and under a pressure of 4 atm is expanded adiabatically to 1 atm in such a way that the temperature of the gas falls to 90 K just above its normal boiling point C of O g is 28 2 JK mol and is constant over the required temperature range O g is supposed to behave ideally Choose the correct options log 2 0 3010 log 3 0 4771 q 0 W 597J AH 846 J AS 342 18

Select the correct statement s A Compressibility factor for one mole of Vander Waal s gas at critical state is 3 8 B Compressibility factor for two moles of Vander Waal s gas at critical state is 3 C Vander Waal s gas molecule always exerts lower average force per collision or the wall than ideal gas molecule when mixture of one mole of each of them is taken in a container at same temperature D Mixture of two equimolar Vander Waal s gases has critical temperature less

The entropy of a crystal containing one mole of identical molecules was measured to 9 134 J K at OK How many orientations does each molecule have in the crystal b Draw a molecule which would be expected to exhibit such behavior

100 ml of 0 1 M HCI is neutralised by 50 ml 0 2 M NaOH solution at 25 C The temperature of the final solution is increased by specific heat capacity of H O 4 2 JK g Assume density of final solution density of water and Mass of final solution Mass of water 1 0 2 K 2 9 K 3 09 K 4 4 2 K

1 mol of monoatomic ideal gas is compressed point A P 8 L 75 K to B P2 1 L T K in reversible adiabatic process If gas is expanded irreversibly and adiabatically from B to C P3 8 L and T K against the constant external pressure of 1atm Select the correct statement s Take 1atm L 101 3 J and R 8 31 J mol K 1 T3 T 75 K 2 T T 75 K 3 Magnitude of work done in A to B is more than that of B to C 4 Magnitude of work done in A to B is less than that of B to C

24 550 kJ cycle 1 work is done by 1 mol of an ideal gas in a cyclic process The amount of heat absorbed b the system in one cycle is 1 550 kJ 3 1100 kJ 2 550 kJ 4 Zero

of attraction between its particles The latent heat which we supply is used up in overcoming the forces of attraction between the particles of a substance during the change of state The latent heat does not increase the kinetic energy of the particles of the substance And since there is no increase in the kinetic energy of the particles the temperature of a substance does not rise during the change of state

Calculate the temperature of the system once equilibrium has been reached Assume that Cpm for H O 1 is constant at its values for 298 K 75 3 J mol K throughout the temperature range of interest A Hus for ice is 6010 J mol 1 Express the temperature in kelvins to three significant figures VAX

One quantum is absorbed per gaseous molecule of X for converting it into X atoms If light absorbed has wave length 1240A then bond energy of X will be 1 10 eV molecule 2 20 J mole 3 48 eV molecule 4 184 J mol

2 58 Fixed amount of an ideal gas contained in a sealed rigid vessel V 24 6 litre at 1 0 bar is heated reversibly from 27 C to 127 C The change in Gibb s energy is J AG in Joule if entropy of gas S 10 10 T J K

for which of the following processes reaction entropy change is negative A Stretching of rubber band B C D Boiling of egg BaCl Na SO BaSO 2NaCl aq q ppt aq Dissociation of 1 mole of dihdyrogen gas into

Q 58 Fixed amount of an ideal gas contained in a sealed rigid vessel V 24 6 litre at 1 0 bar is heated reversibly from 27 C to 127 C The change in Gibb s energy is J AG in Joule if entropy of gas S 10 10 T J K

12 In comparison to a 0 01 M solution of glucose the depression in freezing point of a 0 01 M MgCl2 solution is i the same O ii about twice O iii about three times O iv about six times

For a reaction AP the plots of A and P with time at temperatures T and T are given below 10 A mol L S T T B C AH 0 AS 0 10 AGO 0 AH 0 P mol L AGO 0 AS 0 5 Time Time If T T the correct statement s is are Assume AH and AS are independent of temperature and ratio T of nk at T to In K at T then 2 Here H S G and K are T FA enthalpy entropy Gibbs energy and equilibrium constant respectively T T 2

b 8 0 x 102 joules c 4 0 x 10 2 joules d 1 2 x 10 3 joules he work done in joules when 4 5 grams of H202 reacts at 25 C temperature and 1 atmosphere pressure as follows is 2H O 1 O g 2H O 1 b 4 5 10 a 1 63 x 10 c 3 2 x 10 moles of zinc is dissolved in HCI in an open vessel at 25 C Thou d 6 1 10

3 The oxygen in a high pressure cylinder is at 300 K and 100 atm pressure The valve of the cylinder is opened and the gas is allowed to expand to an atmospheric pressure of 1 atm Assuming that the expansion is adiabatic and conducted under condi tions of constant enthalpy estimate the final temper ature of O after expansion Do not assume O to be an ideal gas

2 5 a A piston cylinder arrangement filled with 25 g of ideal gas at 15 C The piston is displace y a distance of 50 mm by applying a mean force of 250 N During the compression process th emperature rises to 25 C Calculate the heat transfer during the process Assume Cy 720 J kg K

List I I Condensation at normal melting point 1 atm II Fusion at normal boiling point 1 atm III Vaporisation at triple point IV Freezing at normal melting point 1 atm List II P AG 0 Q AG 0 R AS 0 system S AS 0 Which is correctly matched for an endothermic process A I P S T B II P R T C II P R U D III Q R T system T AS system AS U AS system AS surrounding surroun

A system undergoes a process in which AU 300 J while absorbing 400 J of heat energy and undergoing an expansion against 0 5 bar What is the change in the volume in L a 4 b 5 e 2 d 3 AU 3005 OJ bar

c 3 2 x 10 6 2 moles of zinc is dissolved in HCI in an open vessel at 25 C The work done is a 2 477 kilojoules c 0 0489 kilojoules b 4 955 kilojoules d none d 6

on No 13 40 Then 2 moles of liquid A are mixed with 2 moles of liqui nolar Gibb s free energy of the solution is 1 5 kJ mol The comm value of Gibb s free energy of mixing in kJ is closest to R 8 31 CA O 12 9 200 6469 96 202 900202 900

Consider the following reaction between zinc and oxygen and choose the 3 points correct options out of the options given below 2 Zn s O2 g 2 ZnO s AH 693 8 kJ mol 1 O The enthalpy of two moles of ZnO is more than the total enthalpy of two moles of Zn and one mole of oxygen by 693 8 kJ O The enthalpy of two moles of ZnO is less than the total enthalpy of two moles of Zn and one mole of oxygen by 693 8 kJ O 693 8 kJ mol 1 energy is evolved in the reaction O 693 8 kJ mol 1 energy is absorbed in the reaction

3 For a given reaction energy of activation for forward reaction E is 80 kJmol 1 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 3 1 2 2 0 5 4 2 0

2 33 Calculate the work involved when 1 mol of an ideal gas is compressed reversibly from 1 00 bar to 5 00 bar at a constant temperature of 300 K 1 14 01 kJ 3 4 01 kJ 2 18 02 kJ 4 8 02 kJ

A light source of frequency 6 x 1015 Hz is subjected to a metal sheet having work function equal to 22 6 eV Then the velocity of photo electrons emitted having maximum kinetic energy will be Planck constant h 6 626 x 10 34 J s 1 4 43 x 105 m s 2 3 21 x 107 m s 3 8 89 x 105 m s 4 8 73 x 106 m s

The standard enthalpies of formation of H O 1 and CO g are respectively 286 kJ mol and 394 kJ mol If the standard heat of combustion of CH4 g is 891 kJ mol then the standard enthalpy of formation of CH4 g is A 75 kJ mol B 75 kJ mol C 211 kJ mol D 211 kJ mol E 1571 kJ mol

The surface of copper gets tarnished by the formation of copper oxide N2 gas was passed to prevent the oxide formation during heating of copper at 1250 K However the N gas contains 1 mole of water vapour as impurity The water vapour oxidises copper as per the reaction given In PH PM 0 below 2Cu s H O g Cu O s H g PH is the minimum partial pressure of H in bar needed to prevent the oxidation at 1250 K The value of In PH is Given total pressure 1 bar R universal gas constant 8 J K 1 mol In 10 2 3 Cu s and Cu O s are mutually immiscible At 1250 K 2Cu s 2O2 g Cu O s AG 78 000 J mol 1 H2 g O2 g H O g AGe 1 78 000 J mol G is the Gibbs energy 2018

x 100 J of energy was supplied to a system in an isothermal manner at constant pressure What is the work done during 8 a the process nobl a W 0 c W 100 J qete gninimatab 10 b A d W 200 J MOTOR

1 Pressure of 0 210 bat ar 37 C The vapour pressure of pure liquid vapour pressure of water at 37 C 0 198 bar in bar is 1 0 448 3 0 224 2 44 8 4 2 24

A reversible cyclic process for an ideal gas is shown below Here P V and T are pressure volume and temperature respectively The thermodynamic parameters q w H and U are heat work enthalpy and internal energy respectively RY D Volume V A QAC AUBC and WAB P2 V V A P1 V1 T1 WBC P2 V2 V and qBC AHAC AHCA AUCA and QAC AUBC QBC AHAC and AHCA AUCA B P2 V2 T1 Temperature T C P2 V2 T2

21 rms 3PV M u rms P 1 2 Here P 800 mm 80 cm V 22 600 mL M 71 g mol 273 80 13 6 981 dyn cm 800 3 80 13 6 981 22 600 71 0 1018 x 105 cm s 22 600 12 llustration 5 86 Two flasks A and B have equal volume A is maintained at 300 K and B at 600 K While A contains H gas B has an equal mass of CH4 gas Assuming ideal behaviour for both the gases which of the following statement is true about the velocities of molecules a The molecules in flasks A and B are moving with the same velocity b The molecules in flask A are moving two times faster

IIT JEE Hydroxylamine reduces iron III according to following reaction 20MG 2NH OH Fe N O g T H O 4Fe2 4H Iron II thus produced is estimated by titration w standard permanganate solution The reaction is MnO 5Fe 8H Mn 5Fe 4H O A 10 mL sample of hydroxylamine solution was dilute L When 50 mL of this diluted solution was boiled w excess of iron III solution the resulting solution re 12 mL of 0 02 M KMnO4 solution for complete oxi of iron II Calculate the weight of hydroxylamine of the original solution H 1 N 14 0 16 K 39 Mn 55 Fe 56 IIT JEE An organic compound CH O was burnt with the amount of oxygen needed for complete com to CO and H O The hot gases when cooled to 0 atm pressure measured 2 24 L The water collected cooling weighs 0 9 g The vapour pressure of pure 20 C is 17 5 mm Hg and is lowered by 0 104 mm g of the organic compound is dissolved in 1000 g organic comp

Q 66 following A RO BBT C NH D R OH Q 67 Chloronium ion is formed by the reaction of Alkyl chloride on aluminium chloride B Chlorine on ferric chloride C HCI on AICI D HCI on HNO Q 68 CH CH C Br KOH ag dailt CH Q 67 0 68 A RO B Bf C NH D R OH A AICI TE B dfas a C AICI E D HNO T CH

When 1 0gm equivalent of each acid HA and HB are neutralized separately by NaOH the amount of heat released are 43kJ and 27 kJ respectively Which of the following is incorrect Question Type Single Correct Type 1 2 3 4 Both HA and HB are weak acids Ionisation constant of HA is greater than HB Enthalpy of ionisation of HB is greater than HA Enthalpy of ionisation of HA is greater than HR

1 Topic 1 First Law and Basie Fundamentals Thermodynamics of The correct option for free expansion of an ideal gas under adiabatic condition is a q 0 AT 0 and w 0 2020 b q 0 AT 0 and w 01 c q 0 AT 0 and w 0 d q 0 AT 0 and w 0 2 An ideal gas expands isothermally from 10 m to 102 m at 300 K against a constant pressure of 105 Nm 2 The work done on the gas is INEET Odisha 2019 b 270 kJ d 900 kJ Reversible expansion of an ideal gas under isothermal and adiabatic conditions are as shown in the figure NEET Odisha 2019 a 900 kJ c 900 J 4 APA VA TA B PVT C Pc Vc Tc AB Isothermal expansion AC Adiabatic expansion Which of the following options is not correct 9 a T TA b AS AS othermal nothermal c T TB d W W Under isothermal condition a gas at 300 K expands front 0 1 L to 0 25 L against a constant external pressure of 2 bar The work done by the gas is Given that 1 L bar 100 J 2019 a 30 J b 5 kJ c 25 J d 30 J Three moles of ar spontaneously into va be a Zero c 3 Joules 10 Which of the follow 1 q w 111 w a 1 and IV c I II and C 11 In a closed insula with a paddle to of the followin a AE W c AE 0 W When I mol volume temp If heat suppl statement is a q w b q AU c q v d AU 12

4 None of the above 3 1 mole Al C reacts with H O in a closed vessel at 27 C against atmospheric pressure Work done is 1 1800 cal 3 1800 cal 2 600 cal 4 zero

5 In a vessel containing SO3 SO and O at equilibri some helium gas is introduced so that total pres increases while temperature and volume remain the sa According to Le Chatelier s principle the dissociatio SO

Illustration 6 73 150 mL of 0 5 N nitric acid solution at 25 35 C was mixed with 150 mL of 0 5 N sodium hydroxide Solution at the same temperature The final temperature was recorded to be 28 77 C Calculate the heat of neutralisation of nitric acid with sodium hydroxide

The enthalpy and entropy change for the reaction Br 1 Cl2 g 2BrCl g are 30kJ mol 1 105 JK mol respectively the temperature at which the reaction will be in equilibrium is 1 300 K 2 285 7 K 3 273 K 4 450 K

For a c MK A potass K3A H A solution potassium salt of a tribasic acid a2 az Dissociation constants of acid are K K K h 1 a pH 1 2 pK PK log c az b pH 1 PK PK log c pKw 2 W a2 1 c pH d pH pK pk log c W pK pK log c 2 a1