212 Physical Chemistry for NEET g—$—= aa : Level(L) objective Problems 1. Out of molar entropy (I), specific volume (II), heat capacity (II), volume (Iv), Xtensip roperties are : ty nll (b) 1, I, 1V (©) U, I (d) MH, Iv 2. Out of internal energy (1), boiling point (II), pH (III) and E.M.E of the cell (IV) inten, properties are : (a) LU (b) Il, Il, IV (c) 1, IIL, IV (d) Alll of these 3. Thermodynamic equilibrium involves (a) Chemical equilibrium (b) Mechanical equilibrium (©) Thermal equilibrium (@) All the above simultaneously 4, Which has maximum internal energy at 290 K? (a) Neon gas () Nitrogen gas (c) Ozone gas (a) Equal 5. A 10 piece of iron (C = 0.45 J/g°C) at 100°C is dropped into 25 g of water (C = 4.2/¢C) x 27°C. Find temperature of the iron and water system at ghermal equilibrium. (a) 30°C (b) 33°C (c) 40°C (d) None of these 6. When freezing of a liquid takes place in a system : (a) may have q>0 or q<0 depending on the liquid (b) is represented by q>0 (©) is represented by q<0 (d) has q=0 7. Mechanical work is specially important in systems that contain: (a) gas-liquid (b) liquid-liquid (©) solid-solid (@) amalgam 8. Determine which of the following reactions taking place at constant pressure represen system that do work on the surrounding environment 1. Ag* (aq) +Cl- (aq) —> AgCl(s) Il. NH,C\(s) —> NH,(g) +HCI(g) II. 2NH,(g) —+ N2(g) +3H2(g) @ (b) (©) ‘and I (d) Tand 9. Determine which of the following reactions taking place at constant pressure represtt surrounding that do work on the system environment 1 4NH3(g) +702(g) —> 4NO2(g) + 6H ,0(g) MH. CO(g) +2H9(g) —> CH,OH() IML C(s, graphite) +H0(g) —> CO(g) +H(g) . H,0(s) —> H,0() (a) I, IV (b) and I (© Uv (d) Tand Il, IV A sample of liquid in a thermally insulated container (a calorimeter) is stirred for 2 ht: bY mechanical linkage to a motor in the surrounding, for this process : (a) w<0; q=0; AU =0 (b) w>0; q>0; AU>O (©) w<0; q>0; AU=0 (d) w>0; q=0; AU>0 11. A system undergoes a process in which AU = +300 J while absorbing 400 J of heat enetsY ant undergoing an expansion against 0.5 bar. What is the change in the volume (inL)? (a) 4 (b) 5 (2 (@) 3 10.12 %, .-Agiven mass of gas expands reversibly from the state A to the state THERMODYNAMICS 213 a ‘an ideal gas expands against a constant external pressure of 2.0 atmosphere from 20 litre to aplitre and absorbs 10 kJ of heat from surrounding. What is the change in internal energy of the system? (Given : 1 atm-litre =101.3 J) (a) 40525 (b) 5948 J (© 140525 (a) 9940 J ‘one mole of an ideal gas at 25°C expands in volume from 1.0L to 4.0L at constant temperature. What work (in J) is done if the gas expands against vacuum (Pexternal =0)? @ 4.0 x 10? (b) -3.0 x 107 (©) -1.0 x10? (d) Zero x 25°C, a 0.01 mole sample of a gas is compressed from 4.0 L to 1.0 L at constant temperature. What is the work done for this process if the external pressure is 4.0 bar? (@) 16x10° J (b) 8.0x107 5 (©) 4.0x107 5 @ 1.2109 J . Calculate the work done (in J) when 4.5 g of H,0, reacts against a pressure of 1.0 atm at 25°C 2H,0,() —> 0,(g)+2H,0() (a) -163 x 10? (b) 4.5x107 (© 3.2107 (d) -6.1x 10? . 2 mole of zinc is dissolved in HCl at 25°C. The work done in open vessel is : (a) -2.477kJ (b) -4.955 kJ) (©) 0.0489 kJ (d) None /. Temperature of 1 mole of a gas is increased by 2°C at constant pressure, work done is : @R (b) 2R (©) R/2 @ 3R A sample of an ideal gas is expanded 1m? to 3 m° ina reversible process for which P = KV?, with K =6 bar/m®. Work done by the gas is : (@ 5200 ky (b) 15600 ky (© 52k (d) 5267.6 kJ Ph Bby three paths 1, 2 and 3 as shown in the figure. If wy, w2 and w4 respectively be the work done by the gas along three paths then: (@ wy >w>W, . ©) w, 23. An ideal gas is at pressure P and temperature T in a box, which is kept in vacuum with ina Container. The wall ofthe box punctured. What happens as the gas occupies entire container’ (@) It’s temperature falls (b) Its temperature rises (©) Its temperature remains the same (d) Unpredictable 24. In diagrams (1 to 4), variation of volume wit th chang i . along the path ABCD. The change in internal eneray ere oes Shown. A gas ist energy of the gas will be : D. y c : (1) a A B (1)—>P D, ic y k 4 o | : (4) (3)—>P (a) Positive in all the cases (1) to (4) (b) Positive in cases (1), (2), (3) but zero in case (4) (©) Negative in cases (1), (2), (3) but zero in case (4) (d) Zero in all the casesTHERMODY' AMIS 215 in which the refrigerator is kept the door of a refrigerator is kept oj ets cooled Pt open, the room i ets heated @ neither gets cooled nor gets heated (a) gets cooled or heated depending on the initial temperature of the r ‘oom. 06 The temperature of an ideal gas increases in an : (a adiabatic expansion , oO adiabatic compression fa pean expansion gy. Br two mole of an ideal gas : ae (a) Cy-Cp =R (b) C, -C, =2R : | (©) C,-C, =R - ap, ich of the following expressions is tue for an ideal gas ? on aw @ o(@)-0 OF) ofG)-2 le alt aad © wh, =0 (2) 0 99. Liquefied oxygen at 1 atmosphere is heated from 50 K to 300 K by supplyin g heat at a constant rate. The graph that correctly shows the relationship between temperature and time is : @" ow)" © | @" a t t , t t ‘ab, If w,,w,Ws and Ww, for an ideal gas are magnitude of work done in isothermal, adiabatic, isoburie and isochoric reversible expansion processes, the cormee’ order will be : (a) wy >W2>W3>W4 (b) wy>W2>W1 > M4 (© wy>Wo>Wa> 1 (@) wa> Wi >W2> 4 31. For a closed container containing 100 mole of an ideal gas fitted with movable, frictionless, weightless piston operating such that pressure of gas remains constant at 8.21 atm, which graph represents correct variation of log V vs. log T where V is in litre and T in kelvin. 7 s! , > Kas 'g @ 3| 3| ° i i (45° 30" —Tat rg Too V oT tog T 20 . . 32, A gas expands against a variable pressure given by? =) (where P in atm and V in L). During expansion from volume of 1 litre to 10 litre, the gas undergoes a change in internal energy of 400 J. How much heat is absorbed PY the gas au expan? — 5065. (a) 463 (p) 4660 J o : 33, 2 mole of an ideal gas at 27°C expands jsothermally and reversibly from a volume of 4 litre to ‘40 litre. The work done (in J) by the gas 18 * (a) w=-28.72) (b) w=- 11.488 (Q) w=-5.736 kd (a) w=- 4.9881)“FF NEBT Tre, 26 “Physical Chemistry for ally and reversibly from a pressure of 10 atm x isotherma J 01 erm rer ean lifted through a height of 100 meter?” !*™% *(b) 58.55 kg (c) 342.58 kg (4) None of thay mole of an ideal mono-atomic gas figure. Select the correct 34. 10 mole of ideal ga 300 K. What is the (a) 31842 kg : one 85. A heat engine carties ¢ afi" 800K around the cycle as shown in the option: (a) dag = 450 R and qe, =~ 450 R (b) gay = 450 R and gcy =~ 225R 375R (©) dap = 450 R and Qe (d) das =375R and dea 450R Volume——> What is the final temperature of 0.10 mole monoatomic ideal gas that performs 75 cal of wo 36. adiabatically if the initial temperature is 227°C? (use R =2 cal/K-mol) (a) 250K (b) 300 K (c) 350K (d) 750 K 37. The work done by the gas in reversible adiabatic expansion process is : V. -P,V, @* fo) mat) (© Peva=PVi —(@) None of these 5 : During an adiabatic process, the pressure of gas is found to be proportional to the cube fis absolute temperature. The ratio of (C pm /C,, m) for gas is : 5 4 S 9 Z ay 4 (b) a © 2 (d) 3 38. (a) a 39. A gas expands adiabatically at constant pressure such that T « V~!/2 The value of y (Cym/C,, m) of the gas will be : (a) 1.30 (b) 1.50 (© 1.70 (@ 2 40. For an ideal gas in adiabatic process : (a) Temperature remains constant in expansion process (b) Temperature remains constant in compression process (c) Temperature remains constant in free expansion process (qd) Temperature always decreases in adiabatic process 41. P-V plot for two gases (assuming ideal)during adiabati plot f ] 18 adiabatic processes are given in the Fig, Plot A and plot B should correspond respectively to: Hand Hs an ° (@) Hy and Cl, a a 42. Calculate the final tem; — perature of ic i i i: adiabatically from 16 Lto2L 5 ato] Cs esl ga thats a ™ @) 600K (b) 1044.6 K (©) 1200 K (a) 2400 K«47 50. 51, 52, a7 5 mole of an ideal gas expand isothermally and irreversibly from a pressure of 10 atm to | atm against a constant external pressure of 1 atm. w;,, at 300 K is : (a) 15.921 kJ (b) -11.224 kJ (c) -110.83 kJ (d) None of these with what minimum pressure (in kPa), a given volume of an ideal gas (C,_ =7/2R), originally at 400 K and 100 kPa pressure can be compressed irreversibly adiabatically in order to raise its temperature to 600 K : (a) 362.5 kPa (b) 275 kPa (c) 437.5 kPa (d) 550 kPa . The work done in adiabatic compression of 2 mole of an ideal monoatomic gas against constant external pressure of 2 atm starting from initial pressure of 1 atm and initial temperature of 300 K (R = 2 cal/mol-degree) (a) 360 cal (b) 720 cal (c) 800 cal (d) 1000 cal One mole of an ideal £88( Cy = 2 R) at 300 K and § atm is expanded adiabatically to a final pressure of 2 atm against a constant pressure of 2 atm. Final temperature of the gas is : (a) 270K (b) 273 K (©) 248.5 K (d) 200 K Select incorrect statement for an ideal gas in reversible adiabatic process : (a) AU =W (b) no energy in transferred as heat (©) energy is transferred as heat (d) AU =q 2 moles of an ideal monoatomic gas is expanded adiabatically against constant external pressure 1 atm from 1L volume at 300K to 4L. volume, calculate final temperature of gas R= atmL/K mel] 2 (a) 410K (b) 312K (c) 288K (4) 250K Calculate change in internal energy of gas when 2 moles of monoatomic gas is compressed reversibly and adiabatically from 161 to 2L at 300K. (a) 3600cal (b) 2520 cal (d) 2700cal (a) 5400 cal Calculate average molar heat capacity at constant volume of gaseous mixture contained 2 3 5 mole of each of two ideal gases A(Com 5 ) and B(Com 2 R) : (@R (b) 2R (©) 3R (d) 8R 0.5 mole each of two ideal gases A ( Com 3 8) and B (Cy =3R) are taken in a container and expanded reversibly and adiabatically, during this process temperature of gaseous mixture decreased from 350 K to 250 K. Find AH (in cal/mol) for the process : (a) -100R (b) -137.5R (c) -375R (d) None of these A cyclic process ABCD is shown in P-V diagram for an ideal gas. Which of the following diagram represents the same process?53. 54. 55. 56. 57. 58. 59. 60. 61. Physical Chemistry for NEET A B Cy B @y cy A @y| @ v 8B! A > — + T T s 100 sec to evaporate from a 806 watt. The AH yaporization (c) 4.03 kJ/mol (d) None of these vessel and heater conne of H,0 is : 36 mL. of pure water tak ty, electric source which delive (a) 40.3 ki/mol ——_(b) 43.2 kJ/mol For the reaction : PCls(g) —> PCly() + Cla) § (a) AH = AU (b) AH > AU (o) AH < AU (A) None of these Consider the reaction at 300 K ope H,(g) + Cla(g) —> 2HCI(g); If 2 mole of H, completely react with 2 mole of Cl, to form HCl. What is AU° for this reactcg (a) 0 (b) -185 kJ (c) 370 kJ (d) None of these Which of the indicated relationship is correct for the following exothermic reaction carried ¢, at constant pressure? CO(g) + 3H2(g) —> CHy4(g) +H20(8) (a) AU =AH (b) AU> AH () w<0 (@) q>0 One mole of an ideal gas undergoes a change of state (2.0 atm, 3.0L) to (2.0 atm, 7.0L) wits change in internal energy (AU) =30 L-atm. The change in enthalpy (AH) of the proces Lamm : (a) 22 (b) 38 (c) 25 (d) None of these What is the change in internal energy when a gas contracts from 377 mL to 177 mL unde constant pressure of 1520 torr, while at the same time being cooled by removing 124 Jheat? (a) 40.52 J (b) -83.48 J (c) 248 J (d) None of these For the real gases reaction 2CO(g) +O2(g) —> 2CO,(g); AH = —560 kJ. In 10 litre rt vessel at 500 K the initial pressure is 70 bar and after the reaction it becomes 40 bat The change in internal energy is : (a) 557K (b) -530 kJ (©) 563 kJ (d) None of these One mole of a non-ideal gas undergoes a change of state from (1.0 atm, 3.0 L, 200 K) t0 (#2 atm, 5.0 L, 250 K) with a change in internal energy (AU) = 40 L- ‘1 Ipye! the process in L-atm : 8y (AU) = 40 L-atm. The change in enthalPy (a) 43 (b) 57 Or these Consider the reaction at 300 K (d) None of 15 CoH (D+ 5'Ox(8) —> 6 COn(g) +3H,0(); ay =—3271k) What is AU for the combustion of 1.5 mole of b () - 326728 1 0) 4900.88 (©) - 4906.5 ki , (@) -3274.75 ky For the reaction; FeCO,(s) —> Feoy 7 , ) at 25°C? ° ©OCS) + CO 2(g) | AH = 82.8 kJ at 25°C, what is (AE ox) (a) 82.8 ks (b) 80.32 ky (©) -2394.77 ky (d) 85.28 kJ63 67. 69, 70, 7 7 73, THERMODYNAMICS 219 coment 5x 10° bar Pressure density of diamond and graphite are 3 g/cc and 2 g/cc respectively, at certain temperature ‘7’, Find the value of AU — AH for the conversion of 1 mole of graphite to y mole of diamond at temperature ‘T” ; (a) 100 kJ/mol (b) 50 kmol (c) -100 kJ/mol (d) None of these predict which of the following reaction(s) has a positive entropy change? 1 Ag’ (ag) + Cl" (aq) —> Agcl(s) 1. NH,Cl(s) —> NH3(g) + HCI(g) I. 2NH,(g) —> N2(g) +3H2(g) (a) Land II (b) 1 (c) Wand Ut (d) 1 __ predict which of the following reaction(s) has a negative entropy change? 1. CH4(g) +202(g) —> CO,(g)+2H,0() I. NH3(g) + HCI(g) —+> NH,Cl(s) TI. 2KC10 4(s) —> 2KCIO,(s) + 0,(g) (a) (b) 0 (©) Land I @1 Which of the following reactions is associated with the most negative change in entropy? (a) 2802(g) +O2(g) —> 280,(g) (b) C,H4(g) +H2(g) —> C2H6(g) (© C(s, graphite) +02(g) —> CO,(@) (A) 3CsHa(g) —> CoH When two mole of an ideal gas (c am 3) heated from 300 K to 600 K at constant pressure. the change in entropy of gas (AS) is : @ $Rin2 (b) -3Rin2 (© 5Rin2 @ BRIn2 . Which of the following expression for an irreversible process ? ta as > 4 as = “4 (as< (a as =U T T T T Which of the following expressions is known as Clausius inequality? aq ie F 2PbO(s) [66.5] + 280 (g) [248.2] (a) -113.5 (b) -168.3, (© +725 (d) -149.2 Given 3,S°=~266 and the listed [S%, values] calculate $° for FeO 4(s): 4Fe30 (8) [......1+ 09g) [205] —> 6Fe,0,4(s) [87] @) #14 (b) +1224 (0145.75 (d) 248.25 The entropy change for a phase transformation is : Al AT AH AH + AG (a) —_ 'b) — (c) — — oe or oF = if AH guson =9.95 kJ/mol and (©) 300K Py of fusion is 80 cal/g) at (©) -2.93 yk AS fusion =35.7 J/K-m0!? (d) 298K 0°C and 1 atm is: (@) ~12.25 /K What is the value of (a) 278.7°C (b) 278.7K AS for freezing of 10 8 of H,0(D) (enthal; (a) 12.25 J/K (b) -0.244 J/K Chloroform has AH vpszaion =29.2 ki/mol and boils at 612°. AS. purzauon for chloroform? (a) 87.3 J/mol-K (b) 477.1 J/mol-K (© -87.3 Jymol-K 90g water at 0°C is frozen at constant Presstire. (d) ~ 477.1 J/mol-K entropy change in the process is: ~Tentalby of fusion of ces 5.46 kyo, (a) 1800J/K (b) -100J/K (©) 10/K (@) ~205/K The entropy of vaporization of benzene is 85 JK-! mol'. When 117g benzene vaporizes at i's normal boiling point, the entro Py change of surrounding is : (a) -85JK ! (b) BSxLSIKY (6) 85x15 3K! (4) None of these Which is correct statement? (a) AS, sununding * 0 for endothermic reaction (b) AS yxy) =O for isothermal free expansion (0 AS,ya) <0 for reversible adiabatic expansion (d) None of these87. 89. 9 ai THERMODYNAMICS 221 identify the correct statement regarding entropy a) At absolute zero temperature, the entropy of perfectly crystalline substances is +ve (py atabsolute zero temperature entropy of perfectly crystalline substance is taken to be zero ‘9 at o°C the entropy of a perfectly crystalline substance is taken to be zero (g)Atabsolute zero temperature, the entropy of al crystalline substances is taken to be zero calculate AS for following process : x() —> XO wi00K 200K Given : Melting point of X(,) =100K ; AH pusion =20KJ/mol ; Cp, (X,0) = 10 J/mol.K (a) 26.93 J/K (b) 206.93 J/K (©) 203 JK (d) 206.93 ki/K Fora perfectly crystalline solid C, , = aT®, where a is constant. IfC,,,, is 0.42 J/K mol at 10 K, molar entropy at 20 K is : (@ 042 J/Kmol — (b) 0.14, /K mol (c) 112 /K mol (d) zero Consider the following spontaneous reaction 3X 9(g) > 2X3(g). What are the sign of AH, AS and AG for the reaction? (a) +ve, te, +ve (b) +ve,-ve,-ve —(c) -ve,+ve,-ve (dd) -ve,~ve,- ve For the reaction 2H(g) —> H.(g), the sign of AH and AS respectively are : (a) +,- (b) +, + © -4 (d) -- . Consider the following reaction. CoH + Fou —+ 6C0,(g) + 3H,0(8) signs of AH,, AS and AG for the above reaction will be @ ++ () —4,- O H+ (@) +4,- For the process H,0() S2===> H,0 (3) Select the correct option. (a) AH =-ve, AS = +ve, AV =-ve, AC (© AH =+ve, AS = +ve, AV Consider the following reaction at temperature"? : ve, AV = +ve, AG =0 ve, AV =-ve, AG=0 CH) =CH,(g) + Cla(g) —> CICH,CH,CI(g) A,H?=-2175ki/mol, A,S°=~233.9 J/K-mol Reaction is supported by : @ entropy (b) enthalpy (© both (@) & (b) (4) neither For a process to be spontaneous at constant T and P : (@) (AG) 5ecem Must be negative (b) (AG) system Must be positive (© (AS) sem Must be positive (@) (AS) system Must be negative For a reaction to occur spontaneously : (@) AS must be negative (b) (-AH +T AS) must be positive (© aH + TAS must be negative (d) AH must be negative Which ofthe following conditions regarding a chemical process ensures its spontaneity at all temperature?a (b) A <0, AS >0 0, when . <0,AS< (a) AW OAS 0 (c) AH<0,AS<0 — (d) MH > 0,454 97. The tree energy change AG (a) the system is at equilibrium (e) reactants are initially mixed th 98, Which of the following conditions will always (a) AW and AS both ve (e) AH and AS both ve 99. Which of following conditions will always (a) AM and AS both ¢ve (b) AH is -ve and AS is +ve (©) AM and AS both -ve (d) AH is +ve and AS is -ve 100. Suppose that a reaction has AH =~ 40 kJ and AS = ~ 50 J/K. At what temperature range yj, change from spontaneous to non-spontaneous? : (a) OS Kto1K (b) 799 Kto 800K = (c) 800 Kto 801K (d) 799 Kto 801x 101. For isothermal expansion in case of an ideal gas : (a) AG = AS (b) AG = AH (c) AG=-T.AS d) N =-T. lone of 102. What is the normal boiling point of mercury? ame Given : AH’ (Hg, =0; S° (Hg, 1) =77.4 J/K-mol AH; (Hg, g) = 60.8 kJ/mol; S° (Hg, g) = 174.4 J/K-mol son 2 624.8 K (b) 626.8 K © 6368 K (d) None of these 18am of ice is converted into water at 0°C and 1 atm, The entropies of H0(s) and H,0(0a 8.2 and 60 J/mol K respectively. The enthalpy change for thi nis! (a) 5951.4 J/mol (b) 595.14 J/ a ; 14 J/mol 104 (c) -5951.4 J/mol (d@) None of these - Using the listed [G°, values] calculate AG® for the reacti 27 nae 3H,S(g)[-33.6] + 2HNO,(0 [80.6] —s 2NO(g) [486.6] - (a) -513.2 (b) -1037.0 (© +433.4 oe 105. From the following AH® and AS? values, | ich Hose lioceial lues, predict which of reactions (b) catalyst is added horoughly (d) the reactants are completely cop, lead to a non-spontaneous change " (b) AH is -ve and AS is +ve (d) AH is +ve and AS is -ve s lead to a spontaneous reaction? sion is : 20(D [-237.1] + 35(s) [0.0] (d) +225.0 1, Hi, and II would © AH® (kJ) AS® (J, ! +105 ae I +18 1 uu 126 at a) I 106 en E oe (© Wand i Calculate AL for UBry from the AG” of reaction and the $° vay eu values Us) + 2B) —> UB (9); AG? =-788.6 Ks $° G/Kmol Gee (a) -822.1 kJ/mol (b) -841,9 ol) 50.3, 152.3, 242.6 (©) -775.6 ki/mol ata ee 3 kd/mol 107. The entropies of H,() and H(g) are 130.6 and 114.6 J mol! x the data given below calculate the bond energy of Hl (in ku/m, respectively at 298 K. Usins ol) : H3(g) —> 2H(g); AG° = 406.6 kyPS: THERMODYNAMIOS 273 3772 (b) 436.0 (©) 425.5 (d) 430.5 consider the AG; and AH y (kJ/mol) for the following oxides. Which oxide can be most easily Le gecomposed t0 form the metal and oxygen gas? 318.4, AH® =~ 348.3) (b) Cu, (AG" = 146.0, AI 168.5) -58.5, AH® = -90.8) (d) PhO(AG" =— 187.9," 217.4) yop forthe reaction takes place at certain temperature NH ,COONH 4(s) = 2NH (4) 1 GO,(g). equilibrium pressure is 3X bar then A,G° would be (@ -RTIn9 -3RT InX (b) RT In 4 —3K1' In X () -3RTInX (d) None of these 10. Caleulate AG? (KJ/mol) at 127°C for a reaction with K gainhim = 10° (a) -38.294 (b) -16.628 (c) -9.16 (d) None of these 111. When reaction is carried out at standard states then at the equilibrium : (a) AH? =0 (b) As? =0 (©) equilibrium constant K =0 (@) equilibrium constant K = 1 112, At 25°C, AG° for the process H,O(l) =*H,0(g) is 8.6 kJ. The vapour pressure of water at this temperature, is nearly : (a) 24 torr (b) 285 torr (©) 32.17 torr (d) 100 torr 113. For the auto-ionization of water at 25°C, H,0() =® H"(aq) + OH (aq) equilibrium constant is10*. What is AG® for the process? (a) =8x104 5 (b) =3.5x104 J (©) =104J (d) None of these 114. The molar entropies of HI(g), H(g) and I(g) at 298 K are 206.5, 114.6, and 180.7 J mol | K ' respectively. Using the AG° given below, calculate the bond energy of HI. HI(g) —> H(g) +1(g); 4G° =271.8 kJ (a) 282.4 kJ mol (b) 298.3 kJ mol! (©) 290.1 kJ mol (d) 315.4 kJ mol! 115, Hess's law states that : . (a) the standard enthalpy of an overall reaction is the sum of the enthalpy changes in individual reactions. (b) enthalpy of formation of a compound is same as the enthalpy of decomposition of the compound into constituent elements, but with opposite sign. (c) at constant temperature the pressure of a gas is inversely proportional to its volume (@) the mass of a gas dissolved per litre of a solvent is proportional to the pressure of the gas in equilibrium with the solution 116. An imaginary reaction X —» Y takes place in three steps X —> A, AH=-%; B—+ A, AH=-q; B—+ Y, AH - ds If Hess’ law is applicable, then the heat of the reaction (X — Y) is: @ a -a2+% ) a2 - 43 - © a ~-d-4; (d) qy—4 117, The enthalpy change for a reaction does not depend upon a oon (a) the physical states of reactants and products224 Phigaical Chemistry for NEET inoae (b) use of different reactants for the same product (c) the number of intermediate reaction steps ; (d) the differences in initial or final temperatures of involved substances 118. The standard enthalpy of formation 298 Kis 241.82 kJ/mol. Caley at 373 K given the following values ©} the molar heat capaci at constant pressu; H,0(g) = 33.58 JK7 mol; H,(g) = 29.84 JK7 mol™; 02(g) = 29.37 JK™ mol-t Assume that the heat capacities are independent of temperature : (b) — 485.2 kJ/mol (a) -242.6 kJ/mol (d) - 286.4 kJ/mol (© -121.3 kJ/mol 119. Which of the following va t the product is least stable ? (b) -231.6 kcalmol™ (a) -94.0kcalmol™ (d) +64.8kcalmol™ (©) +214kcalmol™ 120. For which of the following substances the enthalpy of formation in the standard state is Jue of AH; represent that (a) Sucrose (b) Ethanol (© Aluminium (d) Calcium chlo 121. in which of the following reaction enthalpy of reaction is equal to enthalpy of format product? (a) CO(g) + Cl(g) —> COCI28) (b) Mg(s) + Bro(g) —> MgBra(9) © N2(9) +3H,(g) — 2NH3(8) , (d) P, (white) +50 9(g) — Py00) 122. Given the following thermochemical equations NO(g) + 05(g) —> NO 2(g) + 0(g); 4-H =-199ki/mol 3 03g) —> 5028); 4,H =-142ki/mol 09(g) —> 20(g); 4,H = 495kJ/mol What is the A,H for the reaction NO(g) + O(g) —> NO 2(g)? 29)? @ -304.5k3/mol eo ) -588.5ks/mol -552.5kJ/mol 123. Given the equations: (a) None of these 1 ° Gr) —> P(g); AH? = +74.2kcal 1 gHo@—>H(g); AH?=+52.1 kcal P(g) + 3H(g) —> . PH4(g); AH?= Determine the overall change in enthalpy a on =-2293kcal p, AH for (a) -48 keal ae —> Pal) + 6H2(8) 124. The value of A /H° for ra 2 2kcal (©) 4+2.2kcal @ ga2.ke#l Given: mo +6Cla(g) ——» 4PCl,(); AH =-1270 kJ (a) 772 peers PCI ;(9); AH =-137 1s (b) -498 kJ/mol (© ~454.5ky/mol 7” py!THERMO ee 125- z 126- 127. 128. 129. 130. 131, calutate heat of formation (in eal) of acetic acid from the following data: 1 cH,COOH(D +2028) 2 4() + 2Hz0(); AH? = -200 kcal 1. o(8.gr) + O29) > CO,(g); AH? = -94 kcal 1g (g) > H,0(D, AH? = ~68kcal m1. H2(9) + 5 (a) -100 (b) -124 (c) -150 (d) -200 Calculate the standard enthalpy of reaction for the following reaction using the listed enthalpies of reaction : 3Co(s) +202(g) —> Cos04(s) 2Co(s) +O2(g) —> 260065); AH; --475.8kI 6C00(s) + 09(g) —> 2.C004(s); AH 2 =~355.0 kJ (a) 891.215 (b) -120.8 kJ (©) +891.2 kJ (@) -830.8 kJ From given following equations and AH® values, determine the enthalpy of reaction at 298 K for the reaction : CoH, (g) + 8F2(g) —> 2 CE,(g) + 4HF(g) H,(g) +Fa(g) —> 2HF(@); AH? =—537 KI C(s) + 2F2(g) —> CF4(g)s AH} =— 680 kJ 2C(s) +2Hy(g) —> Cotty(g); AH =S2kI (a) -1165 (b) -2486 (©) +1165 (d) +2486 Given : (diamond) +O, —> CO2; AH (graphite) +O, —> CO; AH The enthalpy of formation of diamond from graphite is nar ©) -15k5 (©) ~788K) (a) 788k i iar i following equations represents a reaction that provides the enthalpy of formation (a) Cls) +HCK(g) +H2(g) —> CH3Cl(s) (b) C(s) +3H(g) + Cite) —> CH3Cl(g)— * (©) C(s) +3/2H2(g) + 1/2Cla(g) —> CHCl) (d) CH4(g) + Cl2(g) —> CH,CI(g) + HCICg) Use the given standard enthalpies of formation (in ; reaction of the following reaction : {in kdymol) to determine the enthalpy of . NH,(g) + 3F2(g) —> NF3(g) + 3HF(g) AHG (NHq,g)=- 46.2; AH} (NFy,g)=-113.0, AH} (HF, g) =~ 269.0 ® -335.8 kJ/mol (b) -873.8 ki/mol_ (©) -697.2 ki/mol (A The standard enibalpy of formation of octane (CgH yg) is -250 kJ/mol ° len 0.4 ki/mol of combustion of CoH, The enthalpy of formation of CO,(@) and H1,O() are Soe yea (a) - 5200 ‘kJ/mol (b) - 5726 kJ/mol 1 (©) ~ 5476 kJ/mol (4) - 5310 kJ/mol22% Physical Chemistry for NEET. . 132. Determine the enthalpy of formation of BH ¢(g) in kJ/mol of the following Teaction . BHg(g) +3028) —> B,0,(s) + 3H,0(g); Given : A,H°=-1941kJ/mol; AH; (Bz03,s) =- 1273 kJ/mol; AH (H,0, g) =- 241.8 kJ/mol (a) -75.6 (b) +75.6 (©) -57.4 (d) -28.4 133. Consider the following reactions : Cs) +O2(g) —> CO2(g) + xkJ CO(g) + }02(g) —> CO2(g) + ¥ KI The heat of formation of CO(g) is : (a) -(x+ y) ki/mol (b) (x - y) kJ/mol © (y-») ky/mol (d) None of these 134. If A H° (CjH,) and A ¢H° (CH) are x, and x, kcal mol”, then heat of hydrogenation ¢ CoH, is: (a) x +22 (b) x, -x2 © x2.-x, (d@) x, +2x, 135. What amount of energy (kJ) is released in the combustion of 5.8 g of CyH4o(g)? 2C4Hio(g) + 1302(g) —> 8CO,(g)+10H,0(D; AH°=-5756k) (a) 575.6 (b) 287.8 » © 182 (@) 57.56 136. The enthalpy of the reaction forming PbO according to the following equation is 438 kJ. Wht heat energy (kJ) is released in formation of 22.3 g PbO(s)? (Atomic weights : Pb =207,0 =16.0) 2Pb(s) +O2(g) —> 2PbO(s) (a) 21.9 (b) 28.7 © 146 137. The fat, Cs7H 940 6(s), is metabolized via the formation, calculate the A,H® (kJ) when 1.0 g (d) 34.2 following reaction. Given the enthalpies o of this fat reacts, Cs7Hi40 6(8) + 800218) —+ 5700, (g) +52H,0(0 4 pH? (Cs7H 040 6,5) =-70870 ki/mol; A r#H° (30,1) = —285.8 k/mol: A fH? (CO2, g) =-393.5 kJ/mol , (a) AH? =37.98 (©) AH?=33.4 138.The A,;H° of NH,(g) is -46kJ mol. 2NH,(g) —> N2(g) +3H2(g) is : (a) 46 (b) -46 © 92 139. Consider the following reaction: (a) -92 (b) AH? = 40.4 (@) AH? = 30,2 The AH (in kJ mol!) of the reacio® , H200 — H,0(8); aH, = 4445 2CH,OHJ + 30,8) —> 41,000 + 260,09). ayy What i the value of Af! for second reaction if water vapour ingren, product? | | (a) -1409 kJ ©) ~1629 kg (© 12771 BBN None of these 2=-1453 kJ « of liquid water is formedTHERMODYNAMICS 227 40. The standard enthalpy change for the following reaction is 436.4 kJ : H2(g) —> H(g) +H(g) What is the A yH® of atomic hydrogen (H)? (a) 872.8 kJ/mol (b) 218.2 kJ/mol (0 -218.2 kJ/mol (d) - 436.9 kJ/mol 141. Determine enthalpy of formation for HO (I), using listed enthalpies of reaction : NH,( +2H,0,(0 —> N2(g)+4H,0(0; A,H{ =-818 kJ/mol N2H,(D +09(g) —> N,(g)+2H,0(); A,H} =-622 kJ/mol H,(g) +1/202(g) —> H,0(0; A,H3 =-285 kJ/mol (a) -383 kJ/mol (b) -187 kJ/mol (c) -498 kJ/mol (d) None of these 142. Heat of combustion of ethanol at constant pressure and at temperature T K is found to be -qJmol). Hence, heat of combustion (in J mol”) of ethanol at the same temperature at constant volume will be : (@ RT-q (b) -(q+ RT) (© q-RT (d) q+RT 143. The difference between heat of reaction at constant volume and heat of reaction at constant pressure for the formation of 1 mole of CgH;COOH (J at 300K, will be: (a) 24x10 cal (b) -24 x 10? cal (©) 18 x10? cal (d) -3 x 107 cal 144. The molar enthalpy of formation for two oxides of nitrogen at 1000K are NO,(g) =32kJmol™? and NO(g) =90 kJ mol? For the reaction 2NO 2(g) —> 2NO(g) + 0(8) AU at 1000K would be: (Given: R =8 J/K - mol ) (@) 108ks (b) -108KJ (©) 124k (@ 116k 148. AH for vaporization of a liquid at its normal boiling point 227°C is 4.0 kcal mol~. Calculate change in internal energy (in kcal) of 2 moles of the liquid under these conditions. (@) 6 (b) 12 4 (d) 10 146. 24.631 of CH, gas is combusted at 1atm pressure & 300°C temperature, then heat released at constant pressure due to combustion is 280kJ, then calculate heat of combustion of 1gm of CoH, (g) (a) 10K (b) 20 kJ (© 280k (@) 5kI 147, Stearic acid [CH ,(CH 2),5CO 2H] is a fatty acid, the part of fat that stores most of the energy. 1.0 g of stearic acid was burned in a bomb calorimeter. The bomb had a heat capacity of 652 IPC. If the temperature of 500 g water (c = 4.18 J/g °C) increase from 25.0 to 39.3°C, how much heat was released when the stearic acid was burned? [Given C, (H0) = 4.18 J/e°C] (@) 39.21 (b) 29.91 kJ © 108 kg (a) 9.3210 148. Gasoline has an enthalpy of combustion 24000 kiJ/ gallon. When gasoline burns in an automobile engine, approximately 30% of the energy released is used to produ i work. The remainder is lost as heat transfer to the engine's § eee estimating how much heat transfer is required, calculate what fone eed bbe heated from 25°C to 75°C by the combustion of 1.0 gallon of gasoline in an auromobile? (Given : C (1,0) = 4-18 J/g°C) : (eo 3445 kg (b) 80.383 kg © 22 kg (@) 224 kgbe a] Physical Chemistry for NEET ic acid is added to 0.05 L of 0.2 chloric acid is a d 0.2 M a, 149. A 0.05 1 sample of 0.2 M aqueous pa of entire calorimeter system is 489 yet * ammonia in a calorimeter. Pas ‘He in ki/mol for the following reaction.” temperature increase is 1.09 K. Calcul r NH,Cl(aq.) HCI(aq.) + NH3(aq.) ©) 611 (c) -55.8 (d) -58.2 (a) -52.32 ae is d beaker of mass 92g made ci ists of an insulate: UP of g, 150. A constant pressure calorimeter ae aker contains 100mL of 1M HCl at 23¢¢,° vhs with heat capacity 0.75 JK “'g7'. _ is he final temperature after the reaction is complete 100mL of 1M NaOH at 23°C is added. The final | t is 29. $C What is AH per mole for this neutralisation reaction? Assume that the heat capacities 29.3°C. ifi = “le of all solutions are equal that of same volume of water. [Specific heat of water 4.184 Jg-l¢-1 ) (a) -S7.06kJ (b) -56.5kJ (c) -55kJ (d) -52ky . 151. A coffee cup calorimeter initially contains 125 g of water, at a temperature of 24.2°C, 8 of ammonium nitrate (NH ,NO 3), also at 24.2°C, is added to the water, and the final temperature 's 18.2°C. What is the heat of solution of ammonium nitrate in kJ/mol? The specific heat capacity of the solution is 4.2 J/°C g. (a) 33.51 kJ/mol (b) 39.5 kJ/mol (©) 32.2 kJ/mol (d) 37.3 kJ/mol 152. Read following statement(s) carefully and select the right option : (© The enthalpy of solution of CaCl-6H,0 in a large volume of water is endothermic to the extent of 3.5 keal/ mol. If AH =~ 23.2 kcal for the reaction, CaCl, (s) + 6H,0() —, CaCly.6H,0(s) then heat of solution of CaCl, (anh (I) For the reaction 2CI(g) + Ci. (a) statement I and II both are wrong ©) both are correct (©) only J is correct () only 11 is correct 153. If the enthalpy of formation and enthalpy of solution of Hck -75.14 ‘Gym respectively then find enthalpy of fonmerien OIC) re 923 kY/mol and ~75. (a) -17.16 kJ/mol (b) ~167, (©) 17.16 kJ/mol @ None of a 154. At 25°C, 1 mole of MgSO, was dissolved in water, th One mole of MgSO, -7H30 on dissolution gives Se saved cele aa accompanied by an absorption of 13.8 kJ, The enthalpy of hy cdratio of the same composi vi cl MgSO 4(s) +7H,0@) —_, ME80 714,04 be, AH for the rea (2) 105 kiymol_ (6) ~7.4 kYmol—_() 105 mo 155. If the heat of dissolution of anhydrous CuSO, and Cuso 2.8 kcal/mol respectively then the hi drous) ina large volume of water is — 19.7 kcal/mol (d) None of these eat of hydration of ie 120 is -15.89 keal/mol and of , (a) +1869 keal ©) ~18.69 o,,4 °° form Cuso, -5H,0 is: (©) +13.69 cal () ~13.¢6 i 186. The enthalpies of neutralization of a weak b. a vel WOH and a ~12250 cal/mal and -13000 cal/mol Tespectively. When, Strong containing 1 mole of AOH and 1 mole of BOM, che enthor® Mole what ratio is the acid distribution between AOH and B (@) 2:1 (b) 2:3 © lig base BOH by HCl a chase HClis added toa solutiet OH? M8 was ~12509 cal/ mol-MERRIE EE eer: THERMODYNAMICS 229 casera 157. The magnitude of enthalpy change for neutralization of the reactior Mg0(9) + 2HCKaq) —> MgCl,(aq) +400) Given H* (aq) + OH" (aq) —> H,0(); -57 kJ/mol) will be : (a) less than 57kJ mol : (b) -57kJ mol! (c) greater than 57 kJ mol! (d) 57kJ mol! 158. Enthalpy of neutralization of HCl by NaOH is -55.84 kJ/mol and by NH The enthalpy of ionization of NH,OH is : {a) 107.18 kJ/mol (b) 4.5 kJ/mol (©) -4.5 kJ/mol (d) None of these 159. Enthalpy of neutralisation of H,PO, acid is -106.68kJ/mol using NaOH. Enthalpy of neutralization of HCI by NaOH is ~55.84kJ/mol. Calculate AH jgnicaion Of H4PO 3 into its ions: (a) 50.84kJ/mol (b) SkJ/mol (c) 2.5kJ/mol (d) None of these 160. Which of the following acid will release maximum amount of heat when equal volume of acid is completely neutralised by strong base NaOH? (a) 1M HCl (b) 1M HNO, (1M HClO, (@ 1MH,80, 161. The enthalpy of solution of KCl at 25°C is 17.2kJ/mol and standard enthalpy of formation of KCl(s) is -435.9kJ/mol. If A pH? (Cl ,aq) =s-163.5kJ. Calculate standard enthalpy of formation of K* (aq) ion. 4OH is -51.34 kJ/mol. (a) 255.2kJ/mol (b) +288.7kJ/mol (©) -2552kJ/mol (d) Zero 162. Which of the following reaction is endothermic ? (a) CaCO, —> Cad + CO, (b) Fe +S —> FeS (©) NaOH + HC1—> NaCl +H,0 @ CH, +20, > CO, +2H,0 163. Which of the following is not correct ? (a) Dissolution of a salt in excess of water may be endothermic process (b) Neutralisation is always exothermic (©) The absolute value of enthalpy (H) can be determined by calorimeter (d) The heat of reaction at constant volume is denoted by AE 164. Substance A,B(g) can undergoes decomposition to form two set of products : >> A2(8) + B(g); AH° = 40 kJ/mol A,B(g)— —* A(g) + AB(g); AH° =50 kJ/mol If the molar ratio of A2(g) to A(g) is 5 : 3 in a set of product gases, then the energy involved in the decomposition of 1 mole of A2B(g) is : (a) 48.75 kJ/mol (b) 43.73 kJ/mol (©) 46.25 kJ/mol (d) None of these 165, Boron can undergo the following reactions with the given enthalpy changes : 3 2B(s) + 502(8) —> B,05(9; AH =-1260 1s 2B(s) + 3H2(g) —> BH,(g); AH =30kI"Pil chan or SET Assume no other reactions are ee ee i i ‘ating at const If in a container (operat © SUtroung A of H, (gas) and O, (gas) are passed over excess of ao then calculate the Molt mixture of Hy iner do not change : 7 if the container a aro (© 1:42 (@) 1:84 166. The enthalpy change for the following reaction is 368 kJ. Calculate the average O_p in enerey. OF(g) —> O(g) + 2F(g) (a) 184 kJ/mol (b) 368 kJ/mol (©) 536 kJ/mol (d) 736 kiymol 167. The enthalpy change for the reaction, CxH6(g) —> 2C(g) + 6H(g) is X kJ. The bond enery of C—H bond is : = ps ee (@) data insuticen @> (b) 5 © 6 168. The table given below lists the bond dissociation energy (E gis) for single covalent bonds formed between C and atoms A, B,D,E. Bond E diss (keal mol!) Cc—A 240 ‘ c—B 382 c—D 276 CE 486 Which of the atoms has smallest size ? @bD O)E OA 169. Calculate P—c] bond enthalpy (d) D Given : 45H (PCl3, g) =306 kJ/mol; 4H stomization (P, §) = : 4H (Cl, 8) =121 k/mol mason (9) =314 ki/mol; (a) 123.66 kJ/mol © 19 k4/mol a Nome gat 170. The heat of atomisation OfPH (8) is 228 keal mo|-1 dthat «se. nm energy of the P—P bond is (in kcal); St OF P2H 4(g) is 355 keal mol”. (a) 102 (b) 51 © 26 171. Given: Bond energy (in kJ mol~ By (d) 204 C—H: 410; C—0:350; O—H: 460 4 vapH (CH 30H) (I) = 35k) mol”! The enthalpy of atomisation of CH 3OH() is (in kg mol~1 (a) -2005 (b) 2005 (©) 2049 172. Given : Bond Energy (in kJ mol"!) (4) 2075 Bond H—H o=0 Oy Bond Energy 435 498 464 O46 Enthalpy of vaporisation of H20,()) =52 kJ mol”, 142THERMODYNAMICS 231 ae the enthalpy of formation of H,0,(0 is (in kJ mol”!) (a) -85 (b) +47 (c) -189 (d) -127 178. Calculate the enthalpy for the following reaction using the given bond energies (kJ/mol) (C-H = 414; H—O = 463; HCl = 431, C—Cl =326; C—O =335) CH ,—OH(g) + HCI(g) —> CH,—Cl(g) + H20(g) (a) -23 kJ/mol (b) -42 kJ/mol (¢) -S9 kJ/mol (d) -511 kJ/mol 174. Based on the values of B.E. given, A ;H° of NjH,(g) is : Given: NN = 159 kJ mol; H—H = 436k mol” NEN = 941 kJ mol"?; N-H = 398 kJ mol" (a) 711 kJ mol (b) 62 kJ mol (©) -98 kJ mol *(d) -711kJ mol 175. Calculate free energy change when 1 mole of NaCl is dissolved in water at 300K. Given: Lattice energy of NaCl =778kJ/mol Hydration energy of NaC] =-774.3kJ/mol Entropy change at 300K = 43 J/mol (a) -92kJ/mol (b) 9.2kJ/mol (©) 9200 kJ/mol (d) -39.3 kJ/mol(a) 104. (a) 105. (a) 114 (b) 115. . (a) 12% (c) 125. . (c) 134, 35. (a) (a) 145, . © ‘154, (a) 155. (c) WBA. (b) 165. (a) = (a) ww (2) 194. tb) 175, @ 1% ©) (b) 28 ©) (c) 36, (@) () a ©) @ 56 ©) () 66. (d) () 76. (b) (@) 8% ©) (bo) 98 (bd (b) 136. (a) (a) 146. (b) (b) 156. (a) a (c) (a) . (a) () (b) 103. 113. 123. 139. 148. (c) 158. (b) 189. (d) 168. (b) 169. 140. (t) 150. (2) 160. (d) 470. (0)