Chapter 5

In a flask, colourless \(\mathrm{N}_{2} \mathrm{O}_{4}\) is in equilibrium with brown coloured \(\mathrm{NO}_{2}\) At equilibrium, when the flask is heated at \(373 \mathrm{~K}\), the brown colour deepens and on cooling it becomes less coloured. The change in enthalpy for this reaction is (a) negative (b) positive (c) zero (d) unpredictable

The word standard in molar enthalpy change implies (a) temperature \(298 \mathrm{~K}\) and pressure 1 atm (b) any temperature and pressure 1 atm (c) any temperature and pressure 1 bar (d) any temperature and pressure

\(2 \mathrm{MnO}_{4}^{-}+16 \mathrm{H}^{+}+10 \mathrm{Cl}^{-} \rightarrow 2 \mathrm{Mn}^{2+}\) \(+5 \mathrm{Cl}_{2}(\mathrm{~g})+8 \mathrm{H}_{2} \mathrm{O}\) Above reaction is endothermic and hence the actual temperature of the reaction vessel (isolated from the surrounding) may be different from that expected. Given that the initial temperature of the reaction vessel was used in the calculations, how would, this affect the predicted value of moles of \(\mathrm{Cl}_{2}(n)\) according to equation: \(n=P V / R T\) (a) It would be greater than the actual value (b) It would be less than the actual value (c) It would be the same as the actual value (d) This cannot be determined from the information given

The molar heat capacities of \(\mathrm{A}, \mathrm{B}\) and \(\mathrm{C}\) are in the ratio \(1: 2: 3 .\) The enthalpy change for the reaction \(\mathrm{A}+\mathrm{B} \rightarrow \mathrm{C}\) at temperature \(T_{1}\) is \(\Delta H_{1} .\) Assuming that the heat capacities do not change with temperature, the enthalpy change, \(\Delta H_{2}\), at temperature, \(T_{2}\left(T_{2}>T_{1}\right)\) will be (a) greater than \(\Delta H_{1}\) (b) equal to \(\Delta H_{1}\) (c) less than \(\Delta H_{1}\) (d) greater or less than \(\Delta H_{1}\), depending on the values of \(T_{2}\) and \(T_{1}\).

A quantity of \(1.6 \mathrm{~g}\) sample of \(\mathrm{NH}_{4} \mathrm{NO}_{3}\) is decomposed in a bomb calorimeter. The temperature of the calorimeter decreases by \(6.0 \mathrm{~K}\). The heat capacity of the calorimeter system is \(1.25 \mathrm{~kJ} / \mathrm{K}\). The molar heat of decomposition for \(\mathrm{NH}_{4} \mathrm{NO}_{3}\) is (a) \(7.5 \mathrm{~kJ} / \mathrm{mol}\) (b) \(-600 \mathrm{~kJ} / \mathrm{mol}\) (c) \(-375 \mathrm{~kJ} / \mathrm{mol}\) (d) \(375 \mathrm{~kJ} / \mathrm{mol}\)

A quantity that cannot be directly measured is (a) heat of formation of \(\mathrm{H}_{2} \mathrm{O}(\mathrm{l})\) (b) heat of formation of \(\mathrm{CH}_{4}(\mathrm{~g})\) (c) latent heat of fusion of ice (d) heat of combustion of ethyl alcohol

The heat capacity of bomb calorimeter is \(500 \mathrm{~J} /{ }^{\circ} \mathrm{C}\). A \(2{ }^{\circ} \mathrm{C}\) rise in temperature has been observed on the combustion of \(0.1 \mathrm{~g}\) of methane. What is the value of \(\Delta E\) per mole of methane? (a) \(1 \mathrm{~kJ}\) (b) \(160 \mathrm{~kJ}\) (c) \(-160 \mathrm{~kJ}\) (d) \(-1 \mathrm{~kJ}\)

When 1 g-equivalent of strong acid reacts with strong base, heat released is \(13.5 \mathrm{kcal}\). When 1 g-equivalent \(\mathrm{H}_{2} \mathrm{~A}\) is completely neutralized against strong base, \(13 \mathrm{kcal}\) is released. When 1 g-equivalent \(\mathrm{B}(\mathrm{OH})_{2}\) is completely neutralized against strong acid, 10 kcal heat is released. What is the enthalpy change when 1 mole of \(\mathrm{H}_{2} \mathrm{~A}\) is completely neutralized by \(\mathrm{B}(\mathrm{OH})_{2}\). (a) \(-27 \mathrm{kcal}\) (b) \(-10 \mathrm{kcal}\) (c) \(-20 \mathrm{kcal}\) (d) \(-19 \mathrm{kcal}\)

The enthalpy of neutralization of a strong monobasic acid by a strong monoacidic base is \(-13,700\) cal. A certain monobasic weak acid is \(10 \%\) ionized in a molar solution. If the enthalpy of ionization of the weak acid is \(+400 \mathrm{cal} / \mathrm{mole}\), what is the enthalpy of neutralization of one molar solution of the weak acid? (a) \(-13,700 \mathrm{cal}\) (b) \(-13,340 \mathrm{cal}\) (c) \(-13,660\) cal (d) \(-13,300\) cal

The enthalpy of formation of ammonia gas is \(-46.0 \mathrm{~kJ} / \mathrm{mol}\). The enthalpy change for the reaction: \(2 \mathrm{NH}_{3}(\mathrm{~g}) \rightarrow \mathrm{N}_{2}(\mathrm{~g})+3 \mathrm{H}_{2}(\mathrm{~g})\) is (a) \(46.0 \mathrm{~kJ}\) (b) \(92.0 \mathrm{~kJ}\) (c) \(23.0 \mathrm{~kJ}\) (d) \(-92.0 \mathrm{~kJ}\)

In biological cells that have a plentiful supply of \(\mathrm{O}_{2}\), glucose is oxidized completely to \(\mathrm{CO}_{2}\) and \(\mathrm{H}_{2} \mathrm{O}\) by a process called aerobic oxidation. Muscle cells may be deprived of \(\mathrm{O}_{2}\) during vigorous exercise and, in that case, one molecule of glucose is converted to two molecules of lactic acid, \(\mathrm{CH}_{3} \mathrm{CH}(\mathrm{OH}) \mathrm{COOH}\), by a process called anaerobic glycolysis. \(\mathrm{C}_{6} \mathrm{H}_{12} \mathrm{O}_{6}(\mathrm{~s})+6 \mathrm{O}_{2}(\mathrm{~g}) \rightarrow 6 \mathrm{CO}_{2}(\mathrm{~g})+6 \mathrm{H}_{2} \mathrm{O}(\mathrm{I})\) \(\Delta H^{\circ}=-2880 \mathrm{~kJ} / \mathrm{mol}\) \(\mathrm{C}_{6} \mathrm{H}_{12} \mathrm{O}_{6}(\mathrm{~s}) \rightarrow 2 \mathrm{CH}_{3} \mathrm{CH}(\mathrm{OH}) \mathrm{COOH}(\mathrm{s}) ;\) \(\Delta H^{\circ}=+2530 \mathrm{~kJ} / \mathrm{mol}\) Which of the following statements is true regarding aerobic oxidation and anaerobic glycolysis with respect to energy change as heat? (a) Aerobic oxidation has biological advantage over anaerobic glycolysis by \(5410 \mathrm{~kJ} / \mathrm{mol}\). (b) Aerobic oxidation has biological advantage over anaerobic glycolysis by \(350 \mathrm{~kJ} / \mathrm{mol}\) (c) Anaerobic glycolysis has biological advantage over aerobic oxidation by \(5410 \mathrm{~kJ} / \mathrm{mol}\). (d) Anaerobic glycolysis has biological advantage over aerobic oxidation by \(350 \mathrm{~kJ} / \mathrm{mol}\).

The enthalpy of formation of \(\mathrm{HCl}(\mathrm{g})\) from the following reaction: \(\mathrm{H}_{2}(\mathrm{~g})+\mathrm{Cl}_{2}(\mathrm{~g}) \rightarrow 2 \mathrm{HCl}(\mathrm{g})+44 \mathrm{kcal}\) is (a) \(-44\) kcal \(\mathrm{mol}^{-1}\) (b) \(-22\) kcal mol \(^{-1}\) (c) \(22 \mathrm{kcal} \mathrm{mol}^{-1}\) (d) \(-88\) kcal \(\mathrm{mol}^{-1}\)

The intermediate \(\mathrm{SiH}_{2}\) is formed in the thermal decomposition of silicon hydrides. Calculate \(\Delta H_{\mathrm{f}}^{\circ}\) of \(\mathrm{SiH}_{2}\) from the following reactions: \(\mathrm{Si}_{2} \mathrm{H}_{6}(\mathrm{~g})+\mathrm{H}_{2}(\mathrm{~g}) \rightarrow 2 \mathrm{SiH}_{4}(\mathrm{~g})\) \(\Delta H^{\circ}=-11.7 \mathrm{~kJ} / \mathrm{mol}\) \(\mathrm{SiH}_{4}(\mathrm{~g}) \rightarrow \mathrm{SiH}_{2}(\mathrm{~g})+\mathrm{H}_{2}(\mathrm{~g})\) \(\Delta H^{\circ}=+239.7 \mathrm{~kJ} / \mathrm{mol}\) \(\Delta H_{\mathrm{f}}^{\circ}, \mathrm{Si}_{2} \mathrm{H}_{6}(\mathrm{~g})=+80.3 \mathrm{~kJ} \mathrm{~mol}^{-1}\) (a) \(353 \mathrm{~kJ} / \mathrm{mol}\) (b) \(321 \mathrm{~kJ} / \mathrm{mol}\) (c) \(198 \mathrm{~kJ} / \mathrm{mol}\) (d) \(274 \mathrm{~kJ} / \mathrm{mol}\)

Formation of ozone from oxygen is an endothermic process. In the upper atmosphere, ultraviolet is the source of energy that drives the reaction. Assuming that both the reactions and the products of the reaction are in standard states, the standard enthalpy of formation of ozone from the following information: \(3 \mathrm{O}_{2}(\mathrm{~g}) \rightarrow 2 \mathrm{O}_{3}(\mathrm{~g}), \Delta H^{\circ}=286 \mathrm{~kJ}\), is (a) \(+143 \mathrm{~kJ} / \mathrm{mol}\) (b) \(-143 \mathrm{~kJ} / \mathrm{mol}\) (c) \(+286 \mathrm{~kJ} / \mathrm{mol}\) (d) \(-286 \mathrm{~kJ} / \mathrm{mol}\)

Study the following thermodynamic data given by E. H. P. Cordfunke, A. S. Booji and M. Y. Furkalionk. (i) \(\mathrm{DyCl}_{3}(\mathrm{~s}) \rightarrow \mathrm{DyCl}_{3}(\) aq., in \(4.0 \mathrm{M}-\mathrm{HCl}) ;\) \(\Delta H^{0}=-180.06 \mathrm{kJmol}^{-1}\) (ii) \(\mathrm{Dy}(\mathrm{s})+3 \mathrm{HCl}(\mathrm{aq}, 4.0 \mathrm{M}) \rightarrow \mathrm{DyCl}_{3}\) \((\mathrm{aq}\), in \(4.0 \mathrm{M}-\mathrm{HCl})+3 / 2 \mathrm{H}_{2}(\mathrm{~g})\) \(\Delta H^{\circ}=-699.43 \mathrm{~kJ} \mathrm{~mol}^{-1}\) (iii) \(1 / 2 \mathrm{H}_{2}(\mathrm{~g})+1 / 2 \mathrm{Cl}_{2}(\mathrm{~g}) \rightarrow \mathrm{HCl}_{\underline{\phantom{xxx}}}(\mathrm{aq},\), \(4.0 \mathrm{M}) ; \Delta H^{\circ}=-158.31 \mathrm{~kJ} \mathrm{~mol}^{-1}\) What is \(\Delta H_{\mathrm{f}}^{0}\) of \(\mathrm{DyCl}_{3}(\mathrm{~s})\) from these data? (a) \(-248.58 \mathrm{~kJ} \mathrm{~mol}^{-1}\) (b) \(-994.30 \mathrm{~kJ} \mathrm{~mol}^{-1}\) (c) \(-3977.2 \mathrm{~kJ} \mathrm{~mol}^{-1}\) (d) \(-1469.2 \mathrm{~kJ} \mathrm{~mol}^{-1}\)

The \(\Delta_{f} H^{\circ}\) for \(\mathrm{CO}_{2}(\mathrm{~g}), \mathrm{CO}(\mathrm{g})\) and \(\mathrm{H}_{2} \mathrm{O}(\mathrm{g})\) are \(-393.5,-110.5\) and \(-241.8 \mathrm{~kJ} \mathrm{~mol}^{-1}\), respectively. The standard enthalpy change (in \(\mathrm{kJ}\) ) for the reaction: \(\mathrm{CO}_{2}(\mathrm{~g})+\mathrm{H}_{2}(\mathrm{~g}) \rightarrow \mathrm{CO}(\mathrm{g})+\mathrm{H}_{2} \mathrm{O}(\mathrm{g})\) is (a) \(524.1\) (b) \(41.2\) (c) \(-262.5\) (d) \(-41.2\)

The value of \(\Delta_{\mathrm{f}} H^{\circ}\) of \(\mathrm{U}_{3} \mathrm{O}_{8}(\mathrm{~s})\) is \(-853.5 \mathrm{~kJ}\) \(\mathrm{mol}^{-1} . \Delta H^{\circ}\) for the reaction: \(3 \mathrm{UO}_{2}(\mathrm{~s})\) \(+\mathrm{O}_{2}(\mathrm{~g}) \rightarrow \mathrm{U}_{3} \mathrm{O}_{8}(\mathrm{~s})\), is \(-76.00 \mathrm{~kJ} .\) The value of \(\Delta_{\mathrm{f}} H^{\circ}\) of \(\mathrm{UO}_{2}(\mathrm{~s})\) is (a) \(-259.17 \mathrm{~kJ}\) (b) \(-310.17 \mathrm{~kJ}\) (c) \(+259.17 \mathrm{~kJ}\) (d) \(930.51 \mathrm{~kJ}\).

The enthalpy of neutralization of a strong acid by a strong base is \(-57.32 \mathrm{~kJ}\) \(\mathrm{mol}^{-1} .\) The enthalpy of formation of water is \(-285.84 \mathrm{~kJ} \mathrm{~mol}^{-1}\). The enthalpy of formation of aqueous hydroxyl ion is (a) \(+228.52 \mathrm{~kJ} / \mathrm{mol}\) (b) \(-114.26 \mathrm{~kJ} / \mathrm{mol}\) (c) \(-228.52 \mathrm{~kJ} / \mathrm{mol}\) (d) \(+114.2 \mathrm{~kJ} / \mathrm{mol}\)

Given enthalpy of formation of \(\mathrm{CO}_{2}(\mathrm{~g})\) and \(\mathrm{CaO}(\mathrm{s})\) are \(-94.0 \mathrm{~kJ}\) and \(-152 \mathrm{~kJ}\), respectively, and the enthalpy of the reaction: \(\mathrm{CaCO}_{3}(\mathrm{~s}) \rightarrow \mathrm{CaO}(\mathrm{s})+\mathrm{CO}_{2}(\mathrm{~g})\) is \(42 \mathrm{~kJ}\). The enthalpy of formation of \(\mathrm{CaCO}_{3}(\mathrm{~s})\) is (a) \(-42 \mathrm{~kJ}\) (b) \(-202 \mathrm{~kJ}\) (c) \(+202 \mathrm{~kJ}\) (d) \(-288 \mathrm{~kJ}\)

The standard enthalpies of formation of \(\mathrm{NH}_{3}(\mathrm{~g}), \mathrm{CuO}(\mathrm{s})\) and \(\mathrm{H}_{2} \mathrm{O}(\mathrm{l})\) are \(-46\), \(-155\) and \(-285 \mathrm{~kJ} / \mathrm{mol}\), respectively. The enthalpy change when \(6.80 \mathrm{~g}\) of \(\mathrm{NH}_{3}\) is passed over cupric oxide is (a) \(-59.6 \mathrm{~kJ}\) (b) \(+59.6 \mathrm{~kJ}\) (c) \(-298 \mathrm{~kJ}\) (d) \(-119.2 \mathrm{~kJ}\)

The standard enthalpies of formation of \(\mathrm{H}_{2} \mathrm{O}(\mathrm{l}), \mathrm{Li}^{+}(\mathrm{aq})\) and \(\mathrm{OH}^{-}(\mathrm{aq})\) are \(-285.8\), \(-278.5\) and \(-228.9 \mathrm{~kJ} / \mathrm{mol}\), respectively. The standard enthalpy change for the reaction is \(2 \mathrm{Li}(\mathrm{s})+2 \mathrm{H}_{2} \mathrm{O}(\mathrm{l}) \rightarrow 2 \mathrm{Li}^{+}(\mathrm{aq})+2 \mathrm{OH}^{-}(\mathrm{aq})\) \(+\mathrm{H}_{2}(\mathrm{~g})\) (a) \(+443.2 \mathrm{~kJ}\) (b) \(-443.2 \mathrm{~kJ}\) (c) \(-221.6 \mathrm{~kJ}\) (d) \(+221.6 \mathrm{~kJ}\)

The enthalpies of formation of \(\mathrm{FeO}(\mathrm{s})\) and \(\mathrm{Fe}_{2} \mathrm{O}_{3}(\mathrm{~s})\) are \(-65.0\) and \(-197.0 \mathrm{kcal} /\) mol, respectively. A mixture of the two oxides contains \(\mathrm{FeO}\) and \(\mathrm{Fe}_{2} \mathrm{O}_{3}\) in the mole ratio \(2: 1 .\) If by oxidation it is changed in to a \(1: 2\) mole ratio mixture, how much of thermal energy will be released per mole of the initial mixture? (a) \(13.4 \mathrm{kcal}\) (b) \(67 \mathrm{kcal}\) (c) \(47.2 \mathrm{kcal}\) (d) 81 kcal

The heat evolved in the combustion of glucose, \(\mathrm{C}_{6} \mathrm{H}_{10} \mathrm{O}_{6}\) is \(-680 \mathrm{kcal} / \mathrm{mol}\). The mass of \(\mathrm{CO}_{2}\) produced, when \(170 \mathrm{kcal}\) of heat is evolved in the combustion of glucose is (a) \(45 \mathrm{~g}\) (b) \(66 \mathrm{~g}\) (c) \(11 \mathrm{~g}\) (d) \(44 \mathrm{~g}\)

Standard molar enthalpy of formation of \(\mathrm{CO}_{2}\) is equal to (a) zero (b) the standard molar enthalpy of combustion of gaseous carbon (c) the sum of standard molar enthalpies of formation of \(\mathrm{CO}\) and \(\mathrm{O}_{2}\) (d) the standard molar enthalpy of combustion of carbon (graphite)

In an ice calorimeter, a chemical reaction is allowed to occur in thermal contact with an ice-water mixture at \(0^{\circ} \mathrm{C}\). Any heat liberated by the reaction is used to melt some ice; the volume change of the ice-water mixture indicates the amount of melting. When solutions containing \(1.0\) millimole each of \(\mathrm{AgNO}_{3}\) and \(\mathrm{NaCl}\) were mixed in such a calorimeter, both solutions having been pre-cooled to \(0^{\circ} \mathrm{C}\), \(0.20 \mathrm{~g}\) of ice melted. Assuming complete reaction in this experiment, what is \(\Delta H\) for the reaction: \(\mathrm{Ag}^{+}(\mathrm{aq})+\mathrm{Cl}^{-}(\mathrm{aq})\) \(\rightarrow\) AgCl(s)? Latent heat of fusion of ice at \(0{ }^{\circ} \mathrm{C}\) is \(80 \mathrm{cal} / \mathrm{g}\). (a) \(-16 \mathrm{kcal}\) (b) \(+16 \mathrm{kcal}\) (c) \(-16\) cal (d) \(+16\) cal

The enthalpy of combustion of methane is \(-890 \mathrm{~kJ}\). The volume of methane at \(0{ }^{\circ} \mathrm{C}\) and 1 atm to be burnt to produce \(2670 \mathrm{~kJ}\) heat is (a) \(33.61\) (b) \(67.21\) (c) \(7.471\) (d) \(11.21\)

Assume that for a domestic hot water supply, \(160 \mathrm{~kg}\) of water per day must be heated from \(10^{\circ} \mathrm{C}\) to \(60^{\circ} \mathrm{C}\) and gaseous fuel propane, \(\mathrm{C}_{3} \mathrm{H}_{8}\), is used for this purpose. What volume of propane gas at STP would have to be used for heating domestic water, with efficiency of \(40 \%\) ? Heat of combustion of propane is \(-500 \mathrm{kcal} / \mathrm{mol}\) and specific heat capacity of water is \(1.0 \mathrm{cal} / \mathrm{K}-\mathrm{g}\). (a) \(896 \mathrm{~L}\) (b) \(908 \mathrm{~L}\) (c) \(896 \mathrm{~m}^{3}\) (d) \(908 \mathrm{~m}^{3}\)

For a specific work, on an average a person requires \(5616 \mathrm{~kJ}\) of energy. How many kilograms of glucose must be consumed if all the required energy has to be derived from glucose only? \(\Delta H\) for combustion of glucose is \(-2808 \mathrm{~kJ} \mathrm{~mol}^{-1}\). (a) \(0.720 \mathrm{~kg}\) (b) \(0.36 \mathrm{~kg}\) (c) \(0.18 \mathrm{~kg}\) (d) \(1.0 \mathrm{~kg}\)

As a \(0.1\) mole sample of solid \(\mathrm{NH}_{4} \mathrm{Cl}\) was dissolved in \(50 \mathrm{ml}\) of water, the temperature of the solution decreased. A small electrical immersion heater restored the temperature of the system by passing \(0.125 \mathrm{~A}\) from a \(15 \mathrm{~V}\) power supply for a period of 14 min. \(\Delta H\) for the process: \(\mathrm{NH}_{4} \mathrm{Cl}(\mathrm{s}) \rightarrow \mathrm{NH}_{4} \mathrm{Cl}(\mathrm{aq})\) is (a) \(-15.75 \mathrm{~kJ}\) (b) \(+15.75 \mathrm{~kJ}\) (c) \(-787.5 \mathrm{~J}\) (d) \(+787.5 \mathrm{~J}\)

The enthalpy of combustion at \(25^{\circ} \mathrm{C}\) of \(\mathrm{H}_{2}(\mathrm{~g})\), cyclohexane(l) and cyclohexene(l) \(\begin{array}{lllll}\text { are }-241, & -3920 & \text { and } & -3800 & \mathrm{~kJ} / \mathrm{mol} \text { , }\end{array}\) respectively. \(\quad\) The enthalpy of hydrogenation of cyclohexene(1) is (a) \(-121 \mathrm{~kJ} / \mathrm{mol}\) (b) \(+121 \mathrm{~kJ} / \mathrm{mol}\) (c) \(-242 \mathrm{~kJ} / \mathrm{mol}\) (d) \(+242 \mathrm{~kJ} / \mathrm{mol}\)

The enthalpy change involved in the oxidation of glucose is \(-2880 \mathrm{~kJ} / \mathrm{mol}\). Twenty five per cent of this energy is available for muscular work. If \(100 \mathrm{~kJ}\) of muscular work is needed to walk \(1 \mathrm{~km}\), what is the maximum distance that a person will be able to walk after eating \(120 \mathrm{~g}\) of glucose? (a) \(19.2 \mathrm{~km}\) (b) \(9.6 \mathrm{~km}\) (c) \(2.4 \mathrm{~km}\) (d) \(4.8 \mathrm{~km}\)

A geyser, operating on LPG (liquefied petroleum gas) heats water flowing at the rate of \(3.0\) litres per minutes, from \(27^{\circ} \mathrm{C}\) to \(77^{\circ} \mathrm{C}\). If the heat of combustion of LPG is \(40,000 \mathrm{~J} / \mathrm{g}\), how much fuel, in \(\mathrm{g}\), is consumed per minute? (Specific heat capacity of water is \(4200 \mathrm{~J} / \mathrm{kg}-\mathrm{K}\) ) (a) \(15.25\) (b) \(15.50\) (c) \(15.75\) (d) \(16.00\)

Equal volumes of one molar hydrochloric acid and one molar sulphuric acid are neutralized completely by dilute \(\mathrm{NaOH}\) solution by which \(X\) and \(Y\) kcal of heat are liberated, respectively. Which of the following is true? (a) \(X=Y\) (b) \(2 X=Y\) (c) \(X=2 Y\) (d) none of these

The reaction of zinc metal with hydrochloric acid was used to produce \(1.5\) moles of hydrogen gas at \(298 \mathrm{~K}\) and 1 atm pressure. The magnitude work done in pushing back the atmosphere is (a) \(596 \mathrm{cal}\) (b) \(894 \mathrm{cal}\) (c) \(447 \mathrm{cal}\) (d) \(298 \mathrm{cal}\)

The enthalpy of formation of \(\mathrm{KCl}(\mathrm{s})\) from the following data is (i) \(\mathrm{KOH}(\mathrm{aq})+\mathrm{HCl}(\mathrm{aq}) \rightarrow \mathrm{KCl}(\mathrm{aq})\) \(+\mathrm{H}_{2} \mathrm{O}(1) ; \Delta H=-13.7 \mathrm{kcal}\) (ii) \(\mathrm{H}_{2}(\mathrm{~g})+1 / 2 \mathrm{O}_{2}(\mathrm{~g}) \rightarrow \mathrm{H}_{2} \mathrm{O}(\mathrm{l}) ; \Delta H\) \(=-68.4 \mathrm{kcal}\) (iii) \(1 / 2 \mathrm{H}_{2}(\mathrm{~g})+1 / 2 \mathrm{Cl}_{2}(\mathrm{~g})+\mathrm{aq} \rightarrow \mathrm{HCl}(\mathrm{aq})\) \(\Delta H=-39.3 \mathrm{kcal}\) (iv) \(\mathrm{K}(\mathrm{s})+1 / 2 \mathrm{O}_{2}(\mathrm{~g})+1 / 2 \mathrm{H}_{2}(\mathrm{~g})+\mathrm{aq}\) \(\rightarrow \mathrm{KOH}(\mathrm{aq}) ; \Delta H=-116.5 \mathrm{kcal}\) (v) \(\mathrm{KCl}(\mathrm{s})+\mathrm{aq} \rightarrow \mathrm{KCl}(\mathrm{aq}) ; \Delta H=+4.4 \mathrm{kcal}\) (a) \(+105.5 \mathrm{kcal} / \mathrm{mol}\) (b) \(-105.5 \mathrm{kcal} / \mathrm{mol}\) (c) \(-13.7 \mathrm{kcal} / \mathrm{mol}\) (d) \(-18.1 \mathrm{kcal} / \mathrm{mol}\)

Enthalpy of neutralization of \(\mathrm{H}_{3} \mathrm{PO}_{3}\) by \(\mathrm{NaOH}\) is \(-106.68 \mathrm{~kJ} / \mathrm{mol}\). If the enthalpy of neutralization of \(\mathrm{HCl}\) by \(\mathrm{NaOH}\) is \(-55.84 \mathrm{~kJ} / \mathrm{mol}\). The \(\Delta H_{\text {ionization }}\) of \(\mathrm{H}_{3} \mathrm{PO}_{3}\) into its ions is (a) \(50.84 \mathrm{~kJ} / \mathrm{mol}\) (b) \(5 \mathrm{~kJ} / \mathrm{mol}\) (c) \(10 \mathrm{~kJ} / \mathrm{mol}\) (d) \(2.5 \mathrm{~kJ} / \mathrm{mol}\)

The standard heat of combustion of propane is \(-2220.1 \mathrm{~kJ} / \mathrm{mol}\). The standard heat of vaporization of liquid water is \(44 \mathrm{~kJ} / \mathrm{mol}\). What is the \(\Delta H^{\text {o }}\) of the reaction: \(\mathrm{C}_{3} \mathrm{H}_{8}(\mathrm{~g})+5 \mathrm{O}_{2}(\mathrm{~g}) \rightarrow 3 \mathrm{CO}_{2}(\mathrm{~g})+4 \mathrm{H}_{2} \mathrm{O}(\mathrm{g}) ?\) (a) \(-2220.1 \mathrm{~kJ}\) (b) \(-2044.1 \mathrm{~kJ}\) (c) \(-2396.1 \mathrm{~kJ}\) (d) \(-2176.1 \mathrm{~kJ}\)

Calculate \(\Delta_{\mathrm{f}} H\) for \(\mathrm{ZnSO}_{4}(\mathrm{~s})\) from the following data: \(\mathrm{ZnS}(\mathrm{s}) \rightarrow \mathrm{Zn}(\mathrm{s})+\mathrm{S}\) (rhombic), \(\Delta H_{1}\) \(=44 \mathrm{kcal} / \mathrm{mol}\) \(2 \mathrm{ZnS}(\mathrm{s})+3 \mathrm{O}_{2}(\mathrm{~g}) \rightarrow 2 \mathrm{ZnO}(\mathrm{s})+2 \mathrm{SO}_{2}(\mathrm{~g})\) \(\Delta H_{2}=-221.88 \mathrm{kcal} / \mathrm{mol}\) \(2 \mathrm{SO}_{2}(\mathrm{~g})+\mathrm{O}_{2}(\mathrm{~g}) \rightarrow 2 \mathrm{SO}_{3}(\mathrm{~g}), \quad \Delta H_{3}\) \(=-46.88 \mathrm{kcal} / \mathrm{mol}\) \(\mathrm{ZnSO}_{4}(\mathrm{~s}) \rightarrow \mathrm{ZnO}(\mathrm{s})+\mathrm{SO}_{3}(\mathrm{~g}), \Delta H_{4}\) \(=55.1 \mathrm{kcal} / \mathrm{mol}\) (a) \(-233.48 \mathrm{kcal} / \mathrm{mol}\) (b) \(-343.48 \mathrm{kcal} / \mathrm{mol}\) (c) \(-434.84 \mathrm{kcal} / \mathrm{mol}\) (d) \(-311.53 \mathrm{kcal} / \mathrm{mol}\)

The value of \(\Delta H_{\text {sol }}\) of anhydrous \(\begin{array}{lllll}\text { copper (II) sulphate } & \text { is } & -66.11 & \mathrm{~kJ}\end{array}\) Dissolution of 1 mole of blue vitriol, [Copper (II) sulphate pentahydrate] is followed by absorption of \(11.5 \mathrm{~kJ}\) of heat. The enthalpy of dehydration of blue vitriol is (a) \(-77.61 \mathrm{~kJ}\) (b) \(+77.61 \mathrm{~kJ}\) (c) \(-54.61 \mathrm{~kJ}\) (d) \(+54.61 \mathrm{~kJ}\)

Study the following thermochemical data: \(\mathrm{S}+\mathrm{O}_{2} \rightarrow \mathrm{SO}_{2} ; \quad \Delta H=-298.2 \mathrm{~kJ}\) \(\mathrm{SO}_{2}+1 / 2 \mathrm{O}_{2} \rightarrow \mathrm{SO}_{3} ; \quad \Delta H=-98.2 \mathrm{~kJ}\) \(\mathrm{SO}_{3}+\mathrm{H}_{2} \mathrm{O} \rightarrow \mathrm{H}_{2} \mathrm{SO}_{4} ; \quad \Delta H=-130.2 \mathrm{~kJ}\) \(\mathrm{H}_{2}+1 / 2 \mathrm{O}_{2} \rightarrow \mathrm{H}_{2} \mathrm{O} ; \quad \Delta H=-287.3 \mathrm{~kJ}\) The enthalpy of formation of \(\mathrm{H}_{2} \mathrm{SO}_{4}\) at \(298 \mathrm{~K}\) will be (a) \(-433.7 \mathrm{k} \mathrm{J}\) (b) \(-650.3 \mathrm{~kJ}\) (c) \(+320.5 \mathrm{~kJ}\) (d) \(-813.9 \mathrm{~kJ}\)

Find the bond energy of \(\mathrm{S}-\mathrm{S}\) bond from the following data: \(\mathrm{C}_{2} \mathrm{H}_{5}-\mathrm{S}-\mathrm{C}_{2} \mathrm{H}_{5}(\mathrm{~g}) ; \Delta H_{\mathrm{f}}^{\mathrm{o}}=-148 \mathrm{~kJ}\), \(\mathrm{C}_{2} \mathrm{H}_{5}-\mathrm{S}-\mathrm{S}-\mathrm{C}_{2} \mathrm{H}_{5}(\mathrm{~g}) ; \Delta H_{\mathrm{f}}^{\mathrm{o}}=-202 \mathrm{~kJ}\) \(\mathrm{S}(\mathrm{g}) ; \Delta H_{\mathrm{f}}^{\mathrm{o}}=222 \mathrm{~kJ}\) (a) \(276 \mathrm{~kJ} / \mathrm{mol}\) (b) \(128 \mathrm{~kJ} / \mathrm{mol}\) (c) \(168 \mathrm{~kJ} / \mathrm{mol}\) (d) \(222 \mathrm{~kJ} / \mathrm{mol}\)

Enthalpies of solution of \(\mathrm{BaCl}_{2}(\mathrm{~s})\) and \(\mathrm{BaCl}_{2} \cdot 2 \mathrm{H}_{2} \mathrm{O}(\mathrm{s})\) are \(-20.6 \mathrm{~kJ} / \mathrm{mol}\) and \(8.8 \mathrm{~kJ} / \mathrm{mol}\), respectively. \(\Delta H\) hydration of \(\mathrm{BaCl}_{2}(\mathrm{~s})\) to \(\mathrm{BaCl}_{2} \cdot 2 \mathrm{H}_{2} \mathrm{O}(\mathrm{s})\) is (a) \(-29.4 \mathrm{~kJ}\) (b) \(-11.8 \mathrm{~kJ}\) (c) \(29.6 \mathrm{~kJ}\) (d) \(11.8 \mathrm{~kJ}\)

Given the bond dissociation enthalpy of \(\mathrm{CH}_{3}-\mathrm{H}\) bond as \(103 \mathrm{kcal} / \mathrm{mol}\) and the enthalpy of formation of \(\mathrm{CH}_{4}(\mathrm{~g})\) as \(-18\) kcal/mol, find the enthalpy of formation of methyl radical. The dissociation energy of \(\mathrm{H}_{2}(\mathrm{~g})\) into \(\mathrm{H}\) (atoms) is 103 kcal/mol. (a) \(-33.5 \mathrm{kcal} / \mathrm{mol}\) (b) \(33.5 \mathrm{kcal} / \mathrm{mol}\) (c) \(18 \mathrm{kcal} / \mathrm{mol}\) (d) \(-9 \mathrm{kcal} / \mathrm{mol}\)

The dissolution of \(\mathrm{CaCl}_{2} \cdot 6 \mathrm{H}_{2} \mathrm{O}\) in a large volume of water is endothermic to the extent of \(3.5 \mathrm{kcal} / \mathrm{mol}\). For the reaction, \(\mathrm{CaCl}_{2}(\mathrm{~s})+6 \mathrm{H}_{2} \mathrm{O}(\mathrm{l}) \rightarrow \mathrm{CaCl}_{2} \cdot 6 \mathrm{H}_{2} \mathrm{O}(\mathrm{s})\) \(\Delta H\) is \(-23.2\) kcal. The heat of solution of anhydrous \(\mathrm{CaCl}_{2}\) in large quantity of water will be (a) \(-26.7 \mathrm{kcal} \mathrm{mol}^{-1}\) (b) \(-19.7\) kcal \(\mathrm{mol}^{-1}\) (c) \(19.7 \mathrm{kcal} \mathrm{mol}^{-}\) (d) \(26.7 \mathrm{kcal} \mathrm{mol}^{-1}\)

Given two processes: (i) \(1 / 2 \mathrm{P}_{4}(\mathrm{~s})+3 \mathrm{Cl}_{2}(\mathrm{~g}) \rightarrow 2 \mathrm{PCl}_{3}(1) ; \Delta H\) \(=-635 \mathrm{~kJ}\) (ii) \(\mathrm{PCl}_{3}(\mathrm{l})+\mathrm{Cl}_{2}(\mathrm{~g}) \rightarrow \mathrm{PCl}_{5}(\mathrm{~s}) ; \Delta H\) \(=-137 \mathrm{~kJ}\) The value of \(\Delta_{\mathrm{f}} H\) of \(\mathrm{PCl}_{5}(\mathrm{~s})\) is (a) \(454.5 \mathrm{~kJ} \mathrm{~mol}^{-1}\) (b) \(-454.5 \mathrm{~kJ} \mathrm{~mol}^{-1}\) (c) \(-772 \mathrm{~kJ} \mathrm{~mol}^{-1}\) (d) \(-498 \mathrm{~kJ} \mathrm{~mol}^{-1}\)

What is the enthalpy change for the isomerization reaction: \(\mathrm{CH}_{2}=\mathrm{CH}-\mathrm{CH}_{2}-\mathrm{CH}=\mathrm{CH}-\mathrm{CH}=\mathrm{CH}_{2}(\mathrm{~A})\) \(\underset{\Delta}{\stackrel{\mathrm{NaNH}_{2}}{\longrightarrow}} \mathrm{CH}_{2}=\mathrm{CH}-\mathrm{CH}=\mathrm{CH}-\mathrm{CH}\) \(=\mathrm{CH}-\mathrm{CH}_{3}(\mathrm{~B})\) Magnitude of resonance energies of \(\mathrm{A}\) and \(\mathrm{B}\) are 50 and \(70 \mathrm{~kJ} / \mathrm{mol}\), respectively. Enthalpies of formation of \(\mathrm{A}\) and \(\mathrm{B}\) are \(-2275.2\) and \(-2839.2 \mathrm{~kJ} / \mathrm{mol}\), respectively. (a) \(-584 \mathrm{~kJ}\) (b) \(-564 \mathrm{~kJ}\) (c) \(-544 \mathrm{~kJ}\) (d) \(-20 \mathrm{~kJ}\)

Calculate \(\Delta_{\mathrm{f}} H^{\circ}\) for aqueous chloride ion from the following data: \(\frac{1}{2} \mathrm{H}_{2}(\mathrm{~g})+\frac{1}{2} \mathrm{Cl}_{2}(\mathrm{~g}) \rightarrow \mathrm{HCl}(\mathrm{g}), \quad \Delta_{\mathrm{f}} H^{\mathrm{o}}\) \(=-92.4 \mathrm{~kJ}\) \(\mathrm{HCl}(\mathrm{g})+n \mathrm{H}_{2} \mathrm{O}(\mathrm{l}) \rightarrow \mathrm{H}^{+}(\mathrm{aq})+\mathrm{Cl}^{-}(\mathrm{aq})\) \(\Delta H^{\circ}=-74.8 \mathrm{~kJ}\) \(\Delta_{\mathrm{f}} H^{\circ}\left(\mathrm{H}^{+}\right.\), aq. \()=0.0 \mathrm{~kJ}\) (a) \(0.0\) (b) \(+83.6 \mathrm{~kJ}\) (c) \(+167.2 \mathrm{~kJ}\) (d) \(-167.2 \mathrm{~kJ}\)

Tungsten carbide is very hard and is used to make cutting tools and rock drills. What is the enthalpy of formation (in \(\mathrm{kJ} / \mathrm{mol}\) ) of tungsten carbide? The enthalpy change for this reaction is difficult of measure directly, because the reaction occurs at \(1400^{\circ} \mathrm{C}\). However, the enthalpies of combustion of the elements and of tungsten carbide can be measured easily. \(2 \mathrm{~W}(\mathrm{~s})+3 \mathrm{O}_{2}(\mathrm{~g}) \rightarrow 2 \mathrm{WO}_{3}(\mathrm{~s}) ; \Delta H\) \(=-1680.6 \mathrm{~kJ}\) \(\mathrm{C}(\) graphite \()+\mathrm{O}_{2}(\mathrm{~g}) \rightarrow \mathrm{CO}_{2}(\mathrm{~g}) ; \quad \Delta H\) \(=-393.5 \mathrm{~kJ}\) \(2 \mathrm{WC}(\mathrm{s})+5 \mathrm{O}_{2}(\mathrm{~g}) \rightarrow 2 \mathrm{WO}_{3}(\mathrm{~s})+2 \mathrm{CO}_{2}(\mathrm{~g})\) \(\Delta H=-2391.6 \mathrm{~kJ}\) (a) \(-38.0\) (b) \(-76.0\) (c) \(-19.0\) (d) \(-1233.8\)

Which of the following salts shall cause more cooling when one mole of the salt is dissolved in the same amount of water? (Integral heat of solution at \(298 \mathrm{~K}\) is given for each solute.) (a) \(\mathrm{KNO}_{3} ; \Delta H=35.4 \mathrm{~kJ} / \mathrm{mol}\) (b) \(\mathrm{NaCl} ; \Delta H=5.35 \mathrm{~kJ} / \mathrm{mol}\) (c) \(\mathrm{KOH} ; \Delta H=-55.6 \mathrm{~kJ} / \mathrm{mol}\) (d) \(\mathrm{HBr} ; \Delta H=-83.3 \mathrm{~kJ} / \mathrm{mol}\)

For an ionic solid \(\mathrm{MX}_{2}\), where \(\mathrm{X}\) is monovalent, the enthalpy of formation of the solid from \(\mathrm{M}(\mathrm{s})\) and \(\mathrm{X}_{2}(\mathrm{~g})\) is \(1.5\) times the electron gain enthalpy of \(\mathrm{X}(\mathrm{g})\). The first and second ionization enthalpies of the metal (M) are \(1.2\) and \(2.8\) times of the enthalpy of sublimation of \(\mathrm{M}(\mathrm{s})\). The bond dissociation enthalpy of \(\mathrm{X}_{2}(\mathrm{~g})\) is \(0.8\) times the first ionization enthalpy of metal and it is also equal to one-fifth of the magnitude of lattice enthalpy of \(\mathrm{MX}_{2}\). If the electron gain enthalpy of \(\mathrm{X}(\mathrm{g})\) is \(-96 \mathrm{kcal} / \mathrm{mol}\), then what is the enthalpy of sublimation (in \(\mathrm{kcal} / \mathrm{mol}\) ) of the metal (M)? (a) \(41.38\) (b) \(52.5\) (c) \(48.0\) (d) \(38.27\)