MCQ ON THERMODYNAMICS & ELECTROCHEMISTRY

40 kJ/mole. If the system goes from A to B by a reversible path and returns to state A by an irreversible path what would be the net change in internal energy [CBSE PMT 2003] (a) 40 kJ (b) > 0 kJ (c) < 40 kJ (d) Zero The correct relationship is [DPMT 2002] (a) (b) (c) (d) None of these For ⇌ at ; kJ mol, then is [BVP 2003] (a) 180 kJ (b) 186.4 kJ (c) 165.6 kJ (d) 160 kJ Values of and for five different reactions are given below. Reaction I II III IV V +98.0 – 55.5 +28.3 – 40.5 + 34.7 +14.8 –84.6 –17.0 +24.6 0.0 On the basis of these values predict which one of these will be spontaneous at all tempeature [Kerala PMT 2004; KCET 1988,90] (a) Reaction I (b) Reaction II (c) Reaction III (d) Reaction IV (e) Reaction V Molar heat capacity of water in equilibrium with ice at constant pressure is [IIT JEE 1997] (a) Zero (b) Infinity (c) (d) Internal energy does not include [AIIMS 1999; CPMT 2000] (a) Nuclear energy (b) Rotational energy (c) Vibrational energy (d) Energy arising by gravitational pull Two moles of an ideal gas expand spontaneously into a vacuum. The work done is [AMU 2000] (a) 2 Joule (b) 4 Joule (c) Zero (d) Infinite Heat exchanged in a chemical reaction at constant temperature and constant pressure is called as [BHU 1998; Pb. PET 2000; MP PET 2002] (a) Internal energy (b) Enthalpy (c) Entropy (d) Free energy Which of the following statements is true [KCET 2002] (a) is always greater than (b) is always less than (c) may be lesser or greater or equal to (d) is always proportional to Mass and energy are conserved is demonstrated by [MH CET 2002] (a) First law of thermodynamics (b) Law of conservation of energy (c) Law of conservation of mass (d) Modified form of Ist law of thermodynamics The enthalpy of the reaction, is and that of is . Then [KCET 2004] (a) (b) (c) (d) A reaction occurs spontaneously if [MP PET 2002; CBSE PMT 2005] (a) and bothand are +ve (b) and bothand are +ve (c) and bothand are +ve (d) and is +ve and is –ve Which expression is correct for the work done in adiabatic reversible expansion of an ideal gas [AMU 2002] (a) (b) (c) (d) If an endothermic reaction is non-spontaneous at freezing point of water and becomes feasible at its boiling point, then [AIEEE 2002] (a) is , is +ve (b) and both are +ve (c) and both are –ve (d) is +ve, is –ve What is the entropy change (in ) when one mole of ice is converted into water at (The enthalpy change for the conversion of ice to liquid water is 6.0 kJ at ) [CBSE PMT 2003] (a) 21.98 (b) 20.13 (c) 2.013 (d) 2.198 One mole of (s) on melting absorbed of heat and its entropy is increased by . The melting point of is [DPMT 2004] (a) 1059 K (b) 30.5 K (c) 28.8 K (d) 28800 K The enthalpy change for the process in . If the bond energy of bond in ammonia is . What is the bond energy of bond is [MP PMT 2004] (a) (b) (c) (d) Liquid ammonia is used in refrigeration because of its [DCE 2003] (a) High dipole moment (b) High heat of vaporisation (c) High basicity (d) All of these A cylinder of gas supplied by Bharat Petroleum is assumed to contain of butane. It a normal family requires of energy per day for cooking, butane gas in the cylinder last for …. Days [Kerala PMT 2004] ( of ) (a) 15 days (b) 20 days (c) 50 days (d) 40 days (e) 32 days The heat of neutralization of by under certain condition is – 55.9 kJ and that of by is –12.1 kJ. the heat of ionization of is [MP PET 2001] (a) (b) (c) (d) Equilibrium constant of a reaction is related to [AIIMS 1991] (a) Standard free energy change (b) Free energy change (c) Temperature T (d) None The standard Gibbs free energy change is related to equilibrium constant as [MP PET/PMT 1998] (a) (b) (c) (d) The standard enthalpy or the decomposition of to is 58.04 and standard entropy of this reaction is . The standard free energy change for this reaction at is [DCE 2004] (a) –5.38 kJ (b) 5.38 kJ (c) 5.38 kJ (d) –538 kJ For the equilibrium ⇌ at 1 atm and 298 K [AIIMS 2004] (a) Standard free energy change is equal to zero (b) Free energy change is less than zero (c) Standard free energy change is less than zero (d) Standard free energy change is greater than zero For reaction the value of and . Temperature at which free energy change for reaction will be zero, is [MH CET 1999] (a) 373 K (b) 413 K (c) 463 K (d) 493 K The mass of copper deposited from a solution of by passage of 5 A current for 965 second is (Mol. wt. of Copper = 63.5) [AIIMS 2001] (a) 15.875 g (b) 1.5875 g (c) 4825 g (d) 96500 g The current in a given wire is 1.8 A. The number of coulombs that flow in 1.36 minutes will be [AIIMS 2001] (a) 100 C (b) 147 C (c) 247 C (d) 347 C A solution of a salt of a metal was electrolysed for 150 minutes with a current of 0.15 amperes. The weight of metal deposited was 0.783 gm. The equivalent weight of the metal is [AFMC 2001] (a) 55.97 gm (b) 65.97 gm (c) 75.97 gm (d) 85.97 gm The resistance of 0.01N solution at is 200 (. Cell constant of conductivity cell is 1 cm–1. The equivalent conductance is [CBSE PMT 1999] (a) (b) (c) (d) Which of the following reaction is possible at anode [AIEEE 2002] (a) (b) (c) (d) None of these What is the standard cell potential for the cell for [AIIMS 1980] (a) (b) (c) (d) Normal aluminium electrode coupled with normal hydrogen electrode gives an of . So the standard electrode potential of aluminium is [KCET 1987] (a) – 1.66 V (b) + 1.66 V (c) – 0.83 V (d) + 0.83 V Which one among the following is the strongest reducing agent [BHU 1998] (a) (b) (c) (d) The cell reaction of the galvanic cell is [EAMCET 2003] (a) (b) (c) (d) The specific conductivity of N/10 solution at is and the resistance of cell containing this solution at is 55 ohm. The cell constant is [AIIMS 1999] (a) 1.166 (b) 2.173 (c) 3.324 (d) 4.616 The oxide which is not reduced by hydrogen is [JIPMER 1999] (a) (b) (c) (d) ANS. 1. (d) . 2. (b) . 3. (c) 4. (d) A spontaneous process is accompanied by decrease in enthalpy and increase in entropy means is negative and is positive. 5. (b) , At equilibrium T is constant i.e. thus . 6. (d) . 7. (c) An ideal gas under going expansion in vacuum shows, and . 8. (b) . 9. (c) may be greater or lesser or equal to . 10. (d) It is a modified form of Ist law of thermodynamics. It is a conservation law of mass and energy. 11. (a) for reaction (i) for reaction (ii) So, 12. (b) For spontaneous reaction should be negative If then will be negative and reaction will be spontaneous. 13. (b) . 14. (b) and both are +ve than reaction is spontaneous. 15. (a) 16. (a) ⇌ Given that : By using 17. (a) (So, bond present) means their energy so the bond energy of in 18. (b) Ammonia has high heat of vaporisation hence is used in refrigeration. 19. (e) Calorific value of butane Cylinder consist of butane means of butane gives gives Family need So gas full fill the requirement for 20. (d) 21. (a) 22. (d) . 23. (d) 24. (b) For reaction ⇌ means positive so when is positive then . 25. (c) at equilibrium or . 26. (b) Current (I) = 5A and time (t) = 965 sec. We know that equivalent weight of copper and quantity of electricity passed in coulomb = current × time = 5 × 965 = 4825C. Since 96500 coulombs will deposit of copper therefore 4825 coulombs will deposit = . 27. (b) ; . 28. (a) Time (t) = 150 min = 9000 sec Current (I) = 0.15 A Weight of metal (w) = 0.783 g. We know =. Since 1350 C of electricity will deposited 0.783 g of metal, so, 96500 C of electricity will deposited . 29. (a) 30. (a) Oxidation always occurs at anode. 31. (c) ;. 32. (a) or . 33. (a) The reduction potential of Fe is very high, so it is a strongest reducing agent. 34. (b) . 35. (a) cell constant . 36. (b) On the basis of electrochemical series is not reduced by hydrogen.  THERMODYNAMICS & ELECTROCHEMISTRY Mrs. SHALLU JINDAL AGGARWAL M; 9815208983 SURFACE CHEMISTRY & REDOX REACTION 6 *** Mrs Shallu Aggarwal Mobile #. 98786-08983 *** Reduction Oxidation