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No. of MCQs = 60
C13
MDCAT Total Marks = 60
Unit # 08 (Thermo-Chemistry)
Duration = 60 min
NOTE: Do not write or mark answers on the question paper. Carefully fill in the circle for answer of each question on the OMR answer sheet.

CHEMISTRY
1. The wrong statement among the following is A) Heat of formation B) Heat of reaction
A) An exothermic reaction is B) Electrolysis of water is C) Heat of transition D) All of these
that in which the reacting accompanied with 10. C(diamond) +O 2 ( g ) →C O 2 ( g ) ; ∆ H=−395 kJ
substances have more absorption of energy
energy than the products C(graphite) +O2 ( g ) →C O2 ( g ) ; ∆ H=−393.5 kJ
C) Evaporation of water is an D) The law of conservation of The ∆ H when diamond is formed from graphite
) endothermic change. energy states that the A) –1.5 kJ B) +3.0 kJ
internal energy of a system C) –3.0 kJ D) +1.5 kJ
is constant. 11. 1
2. The correct thermochemical equation is If C ( s )+ O 2 ( g ) → CO ( g ) ; ∆ H =S
2
A) C+ O 2 → CO2 ; ∆ H=−94B) kcal
C+ O2 → CO2 ; ∆ H=+ 94 kcal C ( s )+O ( g ) →C O ( g ) ; ∆ H=R
2 2
C) C (s )+ O (g ) → CO 2( g ) ; ∆ H =−94 ) + O ( g ) → CO 2( g ) ; ∆ H =+94Then,
D) C (skcal kcal the heat of formation of CO
3. Bomb calorimeter is used to determine the heat of reaction A) R + S B) R – S
at C) S – R D) R x S
A) constant pressure B) constant volume 12. Bond energies of (H – H), (O = O) and (O – H) are 105, 120
C) 298 K D) 373 K and 220 kcal/mol, respectively, then ∆ in the reaction is
4. The positive change in enthalpy occurs in equal to
A) 1 B) N 2 ( g ) +3 H 2 ( g ) →2 NH 3 ( g ) 2 H ( g ) +O ( g ) →2 H O(I )
H 2 ( g )+ O 2 ( g ) → H 2 ( g) 2 2 2
2 A) -115 B) -550
C) 1 D) MgCO 3 ( s ) → MgO ( s ) +CO 2(g)
C) -118 D) -130
H 2 ( g )+ O 2 ( g ) → H 2 O(I ) 13. On the basis of the thermochemical equations
2
5. Heat of solution is defined as H 2 O ( g ) +C ( s ) → CO ( g ) + H 2 ∆ H=131kJ
A) Heat required in dissolving B) Heat evolved when 1 mole 1
1 mole in excess of water. is dissolved in excess of CO ( g )+ O2 ( g ) → C O2 ( g ) ∆ H=−282 kJ
2
water.
1
C) Change in heat content of D) None of the above H 2 ( g )+ O 2 ( g ) → H 2 O ( g ) ∆ H =−242 kJ
the system when 1 mole of 2
the solute is dissolved in C ( s )+O2 ( g ) →C O2 ( g ) ∆ H= X kJ
excess of water so that The value of X will be
further dilution of solution A) 393 kJ B) -655 kJ
does not bring any heat C) -393 kJ D) 655 kJ
change 14. From the following data, the heat of formation of PCl5
6. When ammonium chloride is dissolved in water the solution 2 P ( s )+ 3C l2 ( g ) →2 PC l 3 ( g ) ; ∆ H =151.8 kcal
becomes cold because
A) Heat of solution of B) Heat of solution of PC l 3 +C l 2 ( g ) → PC l 5 ( g ) ; ∆ H=−32.8 kcal
ammonium chloride is ammonium chloride is A) -108.7 kcal B) -217.4 kcal
negative positive. C) +217.4 kcal D) +108.7 kcal
C) Heat of dilution of D) Heat of formation of 15. Molar heat capacity of water in equilibrium with ice at
ammonium chloride is ammonium chloride is - constant pressure is
positive positive. A) Zero B) 40.45 kJ/K – mol
7. ∆ H for the transition of carbon in the diamond form to C) infinity D) 75.48 J/k–mol
carbon in the graphite form is –453.5 cal. This suggests that 16.
A) Graphite is chemically B) Graphite is more stable than then what would be heat of formation of HCl?
different from diamond. diamond A) - 194 kJ B) + 194 kJ
C) Graphite is as stable as D) Diamond is more stable C) - 97 kJ D) + 97 kJ
diamond. than graphite. 17. The enthalpy changes for two reactions are given by the
8. Heat of neutralization of any strong acid by any strong base equations below:
is the same because
A) Basically it is the same B) Basically it is the reaction
−¿→ H O ¿
reaction taking place in all of H +¿+OH
2
¿
such cases What is the enthalpy change for the following reactions?
C) Strong acids and strong D) All the above
bases ionize completely in
water. A) + 712 kJ mol-1 B) + 492 kJ mol-1
-1
9. Hess’s law is used in the determination of C) - 492 kJ mol D) - 712 kJ mol-1
18. Some enthalpy changes of combustion are given below:
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 C) D) H+ + H₂O H3O+
H2(g) + → H₂O(l)
- 283
31. 1
Given that, S (s)+6 O 2 ⟶ 4 S O 3 (g) AH = -1590 kJ ,
- 286
2 8
the enthalpy of combustion of sulphur is
- 715 A) -1590 kJ mol-1 B) -3180 kJ mol-1
-1
C) +1590 kJ mol D) -795 kJ mol-1
What is the enthalpy change of the following reaction? 32. The enthalpy change of a reaction does not depend on
A) State of reactants and B) Nature of reactants and
products products
A) - 146 kJ mol-1 B) - 140 kJ mol-1 C) Different intermediate D) Initial and final enthalpy
C) + 140 kJ mol-1 D) + 146 kJ mol-1 reactions change of reaction.
19. What will be the value of for the following 33. The bond dissociation energies of H2, Cl2 and HCI are 104,
reaction at NTP. 58 and 103 kcal respectively. The enthalpy of formation of
MnO2+4HCl MnCl2+Cl2+2H2O HCl gas will be
A) 3RT B) -2RT A) - 44 kcal B) - 88 kcal
C) -RT D) +RT C) - 22 kcal D) - 11 kcal
20. Heat of combustion of C3H8, hydrogen, carbon are -2200 34. For the reaction,
KJ mol-1, -300 KJ mol-1, -400 KJ mol-1 respectively. What is 1
CO ( g )+ O2 ( g ) → C O2 (g) ; Which of the following
standard enthalpy of formation of C3H8? 2
A) - 200 KJ mol-1 B) - 300 KJ mol-1 statements is correct at constant T and P?
C) + 200 KJ mol-1 D) + 300 KJ mol-1 A) B)
21. Which of the following reactions can the bond energy of the C) D) H is independent of the
C – F bond be determined by using only the standard physical states of reactants
enthalpy change of the reaction? 35. Which of the following holds good to the laws of
A) B) thermodynamics for the reaction,
C) D) C H ( g ) +3 O ( g ) → 2 C O ( g)+ 2 H O(l)
2 4 2 2 2
22. If Hf of water is –X kJmol-1. The heat of decomposition of A) B)
water into hydrogen and oxygen gases should be +X kJmol -1. C) D)
The statement forms the basis of 36. The heat absorbed at constant volume is equal to the
A) Ist law of Thermodynamics B) 2nd law of Thermodynamics system's change in
C) Ist law of Thermochemistry D) 2nd law of A) Enthalpy B) Entropy
Thermochemistry C) Free energy D) Internal energy
23. Enthalpy of combustion of a substance is always 37. Mechanical work is specially important in systems which
A) 0 B) 0 contain
C) 0 D) 0 A) Solid-liquid B) Liquid-liquid
24. The value of H for the process C) Solid-solid D) Gases
I(g) + e-(g) I-1(g) is 38. If a reaction involves only solids. and liquids, which of the
A) 0 B) 0 following is true?
A) B)
C) 0 D) 0
C) D)
25. Enthalpy of neutralization of acetic acid with KOH will be
numerically 39. If bond enthalpies of H--H, Br--Br and H--Br bonds are
A) = 57.1 kJ B) > 57.1 kJ 433, 192 and 364 kJ mol-1 respectively. The Ho for the
C) < 57.1 kJ D) Unpredictable reaction H2(g) + Br2(g) → 2HBr(g) is
26. One mole of H2SO4 is completely neutralized with 2 moles of A) - 261 kJ B) + 103 kJ
NaOH in dilute solutions. The amount of heat evolved C) + 261 kJ D) - 103 kJ
during the process is 40. If H+ (aq) + OH- (aq)  H₂O(l) ; H = -57.1 kJ the
A) 57.1 kJ B) > 57.1 kJ neutralization of 1 gram equivalent of H3PO4 acid in dilute
C) < 57.1 kJ D) > 114.0 kJ solutions with KOH will yield heat energy
27. Given the reaction A) = 57.1 kJ B) > 57.1 kJ
C) < 57.1 kJ D) Unpredictable
CO2(g) + H2(g) → CO(g) + H2O(g) ; H = 40 kJ
41. Which of the following equation represents the standard
The H is specifically called heat of formation?
A) Heat of formation of CO B) Heat of combustion A) C(diamond) B) C(graphite)
C) Heat of reaction D) Heat of hydrogenation of +2H2(g)CH4(g) +2H2(g)CH4(g)
C = O bond. C) C(diamond) D) C(graphite)
28. The most random state of H2O system is +4H(g)CH4(g) +4H(g)CH4(g)
A) Ice B) H2O(l) at 80oC ; 1 atm 42. A monoatomic helium molecule possesses
C) Steam D) H2O(l) at 25oC ; 1 atm A) Only potential energy B) Potential as well as
29. Which of the following process should be endothermic? vibrational energy
A) C(s) + O2(g) → CO2(g) B) A+(g) +X-(g) AX(s) C) Vibrational as well as D) Translational as well as
C) O (g) +e O (g)
- - 2-
D) Na+ (g) + e-  Na(g) translational energy potential energy
30. The neutralization of strong acid-strong base in aqueous 43. Change in enthalpy is defined as
solutions can be best represented as A) The change in heat content B) The total energy change at
A) H+ + OH-  H₂O B) Na+ + Cl- → NaCl constant pressure and
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 temperature C) Watson- Crick D) Lowry-Bronsted
C) The heat change at constant D) All are correct 52. The amount of heat absorbed by one mole of solid at 1 atm
volume if ∆n = 0 when it melts into liquid form is denoted by ____________
44. Which of the following statements is wrong? A) Hv B) Hf
A) An endothermic reaction B) During the exothermic C) Hi D) Hs
must absorb energy before it reaction heat is evolved.
can take place.
C) If heat of formation of a D) After an endothermic
53.
compound is negative, the reaction, there is no change
compound is more stable in the temperature of the
than its elements. reaction mixture. What will be the enthalpy change in the above reaction?
45. From the reaction Pwhite  Pred ; ∆H = –18.4 kJ follows that A) 205.5 kJ/mol B) Zero kJ/mol
A) Red P is readily formed B) White P is readily formed C) – 205.5 kJ/mol D) 1 kJ/mol
from white P. from red P. 54. Which of the equations shows the same "twice" the enthalpy
C) White P cannot be D) White P can be converted
converted to red P. into red P and red P is more change of neutralization as the HCl + NaOH NaCl
stable. + H2O
46. Hess’s law of heat summation is an application of A) B)
MgCO3 + 2HCI KOH + HCl KCI +
A) Entropy B) Kirchoff’s law
MgCl2 + CO2 + H2 H2O
C) First law of thermodynamics D) Second law of
C) D)
thermodynamics NH4Cl + NaOH H2SO4 + Mg(OH)2
47. Born Haber cycle enables us to calculate the lattice energy NaCl + H2O + NH3 MgSO4 + 2H2O
of ionic compounds of the type: 55. Which enthalpy change is relevant in the following process:
A) M+X– B) M2X A) Enthalpy of atomization B) Enthalpy of vaporization
C) MX2 D) All of these C) Enthalpy of fusion D) None of these
48. Which of the following processes is endothermic? 56. The Crucible which is used in Bomb Calorimeter is made up
A) the condensation of steam B) the electrolysis of water of
C) the freezing of water D) Ca(s) + 2H2O(l) A) Glass B) Copper
Ca(OH)2(aq) + H2(g) C) Gold D) Platinum
49. Why does the exothermic reaction 57. Given that
(i) C + O2  CO₂ ; H° = -x kJ
C (diamond) C (graphite) H = -3 kJ mol-1 not occur (ii) 2CO + O2  2CO₂ ; H° = -y kJ
spontaneously? The enthalpy of formation of carbon monoxide will be
A) A tetrahedral configuration B) Diamond has only strong A) B)
is always more stable than a covalent bonds whereas
planar one. graphite has both covalent
bonds and van der Waals' C) D)
forces.
C) Graphite has delocalised D) The change from diamond 58.
electrons to graphite has high
activation energy kcal
50. Which statement helps to explain why calcium and chlorine
form CaCI2 rather than CaCI? kcal
A) Less energy is required to B) More energy is released in Find out the heat of formation of SO2
remove one electron from forming chloride ions from A) (y - 2x) B) (2x – y)
the calcium atom than to chlorine molecules in the C) (x + y) D) 2x/y
remove two electrons formation of CaCI2(s) than 59. Energy of activation for the forward reaction is higher
in the formation of CaCI(s) than backward reaction in
C) The lattice energy of D) When CaCI(s) is formed A) Exothermic reactions B) Endothermic reactions
CaCI(s) is less exothermic from its elements, more C) Redox reactions D) Spontaneous reaction
than that of CaCI2(s) energy is released than 60. H 2 +C l 2 ⟶ 2 HCl ; H - 194 kJ. Then, the heat of
when CaCI2(s) is formed
formation of HCl is
from its elements
A) + 194 kJ B) + 97 kJ
51. Lattice energy of binary ionic compounds can be calculated
C) - 97 kJ D) - 194 kJ
by:
A) Born – Haber B) Sidgwick-powel

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