Objective Chemistry for Engineering and Medical Entrance Examinations

K Rama Rao

Chapter 6

Thermochemistry - all with Video Answers

Educators

Chapter Questions

Problem 1

Which of the following statement is false?
(1) Thermochemistry is the study of relationship between the heat energy and chemical energy.
(2) An exothermic reaction is one which is accompanied by evolution of heat.
(3) An endothermic reaction is one in whieh heat is absorbed.
(4) The unit that represents largest amount of energy is electron volt.

Mishal Gul

Mishal Gul

Numerade Educator

Problem 2

The wrong statement among the following is
(1) An exothermic reaction is that in which the reacting substances have more energy than the products.
(2) Electrolysis of water is accompanied with absorption of encrgy.
(3) Evaporation of water is an endothermic change.
(4) The law of conservation of cnergy states that the internal cnergy of a system is constant.

Mishal Gul

Numerade Educator

Problem 3

Which is not characteristic of a thermochemical equation?
(1) It indicates physical state of reactants and products.
(2) It indicates whether the reaction is exothermic or endothermic.
(3) It indicates allotrope of the reactants if present.
(4) It indicates whether a reaction would oecur or not.

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Problem 4

The correct thermochemical cquation is
(1) $\mathrm{C}+\mathrm{O}_{2} \longrightarrow \mathrm{CO}_{2} ; \Delta H=94 \mathrm{kcal}$
(2) $\mathrm{C}+\mathrm{O}_{2} \longrightarrow \mathrm{CO}_{2} ; \Delta H=+94 \mathrm{kcal}$
(3) $\mathrm{C}_{(n)}+\mathrm{O}_{(\mathbb{B})} \longrightarrow \mathrm{CO}_{2 \mathrm{~g}} ; \Delta H=94 \mathrm{kcal}$
(4) $\mathrm{C}_{(8)}+\mathrm{O}_{\mathrm{cg}} \longrightarrow \mathrm{CO}_{2 \mathrm{~m}} ; \Delta H=+94 \mathrm{kcal}$

Mishal Gul

Numerade Educator

Problem 5

For the reactions $\mathrm{H}_{2}(\mathrm{~g})+\mathrm{Cl}_{2}(\mathrm{~g}) \longrightarrow 2 \mathrm{HCl}(\mathrm{g})+X_{1} \mathrm{~kJ}$
$2 \mathrm{IICl}(\mathrm{g}) \longrightarrow 1 \mathrm{I}_{2}(\mathrm{~g})+\mathrm{Cl}_{2}(\mathrm{~g}) \quad X_{2} \mathrm{~kJ}$
(1) $X_{1}$ and $X_{2}$ are numerically cqual.
(2) $X_{1}$ and $X_{2}$ are numerically different.
(3) $X_{1} \quad X_{2}>\mathrm{O}$
(4) $X_{1} \quad X_{2}<0$

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Numerade Educator

Problem 6

Bomb calorimeter is used to determine the heat of reaction at
(1) constant pressure
(2) constant volume
(3) $298 \mathrm{~K}$
(4) $373 \mathrm{~K}$

Mishal Gul

Numerade Educator

Problem 7

${ }^{\text {" }} \Lambda$ " gram of cthanol was subjected to combustion in a bomb calorimeter producing "B" Joulcs of heat; Then
(1) $\Delta U_{\text {crealenion }}=A$ Joules
(2) $\Delta U_{\text {cosimetinn }}=B$ Joules
(3) $\Delta U_{\text {coabustin }}=-\frac{46 B}{A}$ Joules mol $^{-1}$
(4) $\Delta Y_{\text {oxabusiun }}=\frac{46 B}{A}$ Joules $\mathrm{mol}^{-1}$

Mishal Gul

Numerade Educator

Problem 8

The bomb calorimeter is used to find the
(1) heat of combustion
(2) heat of neutralizution
(3) heat of solution
(4) heat of dilution

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Numerade Educator

Problem 9

The cnthalpy change for the formation of $\mathrm{II}_{2} \mathrm{O}(1)$ from its elements in their standard state is $572 \mathrm{~kJ}$; therefore,
(1) the reaction is cndothermic
(2) the sum of the enthalpy of lydrogen and that of oxygen must be greater than that of water(3) the sum of the enthalpy of hydrogen and that of oxygen must be less than that of water
(4) the enthalpy of water must be zero

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Numerade Educator

Problem 10

The false statement among the following is
(1) An exonthermie reaction is spontancous if temperature is too low.
(2) If a teaction is exothermic, the reverse reaction is crudothermic.
(3) The heat lost or gained in a chemical reaction is called free cnergy of the reaction.
(4) Exothermio compounds are stable.

Mishal Gul

Numerade Educator

Problem 11

Which of the following statements is wrong?
(1) An endothermic reaction must absorb energy before it can take place.
(2) During the exothermic reaction heat is evolved.
(3) If heat of formation of a compound is negative, the compound is more stable than its elements.
(4) After an endothermic reaction, there is no change in the temperature of the reaction mixture.

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Problem 12

The false statement among the following is
(1) $\Delta H$ for the thermal decomposition process is always positive.
(2) Bond-breaking cnergy of a molecule is always positive.
(3) Conversion of oxygen into ozone is endothermic reaction and hence it is more stable than oxygen.
(4) The heat change in a chemical reaction is represented by enthalpy change.

Mishal Gul

Numerade Educator

Problem 13

The positive change in enthalpy occurs in
(1) $\mathrm{II}_{2}(\mathrm{~g})+\frac{1}{2} \mathrm{O}_{2}(\mathrm{~g}) \longrightarrow \mathrm{II}_{2}(\mathrm{~g})$
(2) $\mathrm{N}_{2}(\mathrm{~g})+3 \mathrm{II}_{2}(\mathrm{~g}) \longrightarrow 2 \mathrm{NII}_{3}(\mathrm{~g})$
(3) $\mathrm{MgCO}_{3}(\mathrm{~s}) \longrightarrow \mathrm{MgO}(\mathrm{s})+\mathrm{CO}_{2}(\mathrm{~g})$
(4) $\mathrm{H}_{2}(\mathrm{~g})+\frac{1}{2} \mathrm{O}_{2}(\mathrm{~g}) \longrightarrow \mathrm{H}_{2} \mathrm{O}(\mathrm{I})$

Mishal Gul

Numerade Educator

Problem 14

In a chemical reaction if all the reactants and products are in a liquid state then
(1) $\Delta / I>\Delta U$
(2) $\Delta / l<\Delta U$
(3) $\Delta / I=\Delta U$
(4) None

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Numerade Educator

Problem 15

In a flask colourless $\mathrm{N}_{2} \mathrm{O}_{4}$ is in cquilibrium with brown-coloured $\mathrm{NO}_{2} . \Lambda \mathrm{t}$ cquilibrium when the flask is heated at $100^{\circ}$ the brown colour decpens and on cooling it becomes less coloured. Now, the change in enthalpy $\Delta H$ for the system is
(1) Negative
(2) Positive
(3) Zero
(4) none

Mishal Gul

Numerade Educator

Problem 16

The heat of formation is the change in enthalpy accompanying the formation of a substance fromits elements at $298 \mathrm{~K}$ and 1 atm pressure. Since the enthalpies of elements in their most stable state are taken to be zero, the heat of formation of compound is
(1) always negative
(2) always positive
(3) standard heat enthalpy of that compound
(4) zero

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Numerade Educator

Problem 17

From the reaction $P_{\text {white }} \longrightarrow P_{\text {red }} ; \Delta H=18.4 \mathrm{~kJ}$ follows that
(1) Red $\mathrm{P}$ is readily formed from white $\mathrm{P}$.
(2) White $\mathrm{P}$ is readily formed from $\mathrm{red} \mathrm{P}$.
(3) White P cannot be converted to red $P$.
(4) Whitc P can be converted into red $\mathrm{P}$ and red $\mathrm{P}$ is more stable.

Mishal Gul

Numerade Educator

Problem 18

The false statement among the following is
(1) The heat liberated during the neutralization of $\mathrm{a}$ strong acid and a strong base in an aqueous solution is constant.
(2) The heat of combustion is always an exothermic change.
(3) The enthalpies of formation of organic substances can be conveniently determined from heat of combustion data.
(4) Heat of fomation of a compound is equal in magnitude to heat of combustion.

Mishal Gul

Numerade Educator

Problem 19

Ileat of solution is defined as
(1) Heat required in dissolving 1 mole in excess of water.
(2) Heat evolved when 1 mole is dissolved in excess of water.
(3) Change in heat content of the system when I mole of the solute is dissolved in excess of water so that further dilution of solution does not bring any heat change.
(4) None of the above.

Mishal Gul

Numerade Educator

Problem 20

The wrong statement among the following is
(1) The heat change for the reaction $\mathrm{II}_{2} \mathrm{O}(1) \rightarrow$ $\mathrm{II}_{2} \mathrm{O}(\mathrm{g})$ is known as heat of vapourisation.
(2) The heat change in the reaction $\mathrm{C}(\mathrm{s})+2 \mathrm{~S}(\mathrm{~s}) \rightarrow$
$\mathrm{CS}_{2}$ (1) is called heat of formation of $\mathrm{CS}_{2}$.
(3) The standard heat cnthalpy of diamond is zero.
(4) The enthalpy change $\mathrm{C}_{(\mathrm{s})} \rightarrow \mathrm{C}_{(\mathrm{g})}$ is known as cnthalpy of sublimation.

Mishal Gul

Numerade Educator

Problem 21

When ammonium chloride is dissolved in water the solution becomes cold because
(1) Heat of solution of ammonium chloride is positive.
(2) Heat of solution of ammonium chloride is negative.
(3) Heat of dilution of ammonium chloride is positive.
(4) Heat of formation of ammonium chloride is positive.

Mishal Gul

Numerade Educator

Problem 22

The enthalpy of formation of $\mathrm{HI}$ is $30.4 \mathrm{~kJ}$. Which statement is false according to this observation?
(1) HI is an endothermic compound.
(2) For the reaction $\mathrm{H}_{2(\mathrm{~g})}+\mathrm{I}_{2 \mathrm{ig}} \rightarrow 2 \mathrm{HI}_{(\mathrm{g}}, \Delta / I=60.8 \mathrm{~kJ}$
(3) HI is a stable compound.
(4) HI is an unstable compound.

Mishal Gul

Numerade Educator

Problem 23

$\Delta / I$ for the transition of carbon in the diamond form to carbon in the graphite form is $-453.5 \mathrm{cal}$. This suggests that
(1) Graphite is chemically different from diamond.
(2) Graphite is as stable as diamond.
(3) Graphite is more stable than diamond.
(4) Diamond is more stable than graphite.

Mishal Gul

Numerade Educator

Problem 24

If $\mathrm{CII}_{3} \mathrm{COOII}+\mathrm{OII} \longrightarrow \mathrm{CII}_{3} \mathrm{COO}+\mathrm{H}_{2} \mathrm{O}+\mathrm{q}_{1}$
and $\mathrm{II}^{+}+\mathrm{O} \mathrm{II} \rightarrow \mathrm{II}_{2} \mathrm{O}+\mathrm{q}_{2}$, then enthalpy change for
the reaction $\mathrm{CH}_{3} \mathrm{COOH} \longrightarrow \mathrm{CH}_{3} \mathrm{COO}+\mathrm{H}^{+}$ is equal to
(1) $\mathrm{q}_{1}+\mathrm{q}_{2}$
(2) $\mathrm{q}_{1}-\mathrm{q}_{2}$
(3) $\mathrm{q}_{2}-\mathrm{q}_{1}$
(4) $-\mathrm{q}_{1}-\mathrm{q}_{2}$

Mishal Gul

Numerade Educator

Problem 25

The magnitude of heat of solution $\ldots .$ on addition of solvent to solution.
(1) decreases
(2) increases
(3) remains constant
(4) increases or decreases

Mishal Gul

Numerade Educator

Problem 26

IIcat of ncutralization of any strong acid by any strong basc is the same because
(1) Basically it is the same reaction taking place in all such cases.
(2) Basically it is the reaction of $\mathrm{H}^{-}+\mathrm{OH} \rightarrow \mathrm{H}_{2} \mathrm{O}$
(3) Strong acids and strong bases ionize completely in water.
(4) All the above.

Mishal Gul

Numerade Educator

Problem 27

Which of the following about the endothermic compound $\mathrm{C}_{2} \mathrm{II}_{2}$ is false
(1) It is formed with the absorption of energy.
(2) It is an efficient fuel.
(3) If gives off more heat in its combustion than would if it were an exothermic compound.
(4) It is more stable than the exothermic compound $\mathrm{CH}_{4}$

Mishal Gul

Numerade Educator

Problem 28

Ilcat of ncutralization is least in
(1) $\mathrm{NaOH}+\mathrm{CH}_{3} \mathrm{COOH}$
(2) $\mathrm{NaOH}+\mathrm{HCl}$
(3) $\mathrm{NH}_{4} \mathrm{OH}+\mathrm{CH}_{3} \mathrm{COOH}$
(4) $\mathrm{NH}_{4} \mathrm{OH}+\mathrm{HCl}$

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Numerade Educator

Problem 29

Equal volumes of $\mathrm{C}_{2} \mathrm{II}_{2}$ and $\mathrm{II}_{2}$ are combusted under identical conditions. The ratio of their heat of combustion is $\mathrm{H}_{2(g)}+\frac{1}{2} \mathrm{O}_{2(g)} \longrightarrow \mathrm{H}_{2 i \mathrm{~g})} ; \Delta / l=-241.8 \mathrm{~kJ}$
$\mathrm{C}_{2} \mathrm{H}_{2(\mathrm{~g})}+2 \frac{1}{2} \mathrm{O}_{2(\mathrm{~g})} \longrightarrow 2 \mathrm{CO}_{2 \mathrm{~g}}+\mathrm{H}_{2} \mathrm{O}_{\mathrm{k}_{\mathrm{k}}} ; \Delta I I=$
$1300 \mathrm{~kJ}$
(1) $5.37 / 1$
(2) $1 / 5.37$
(3) $1 / 1$
(4) $4 / 5$

Mishal Gul

Numerade Educator

Problem 30

The temperature of $5 \mathrm{~mL}$ of a strong acid increases by $5^{\circ} \mathrm{C}$ when $5 \mathrm{~mL}$ of a strong base is added to it. If $10 \mathrm{~mL}$ of cach are mixed, temperature should increase by
(1) $5^{\circ} \mathrm{C}$
(2) $10^{\circ} \mathrm{C}$
(3) $15^{\circ} \mathrm{C}$
(4) cannot be known

Mishal Gul

Numerade Educator

Problem 31

If $\mathrm{H}_{2 \mathrm{lg} 1} \rightarrow 2 \mathrm{H}(\mathrm{g}) ; \Delta l I=104 \mathrm{kea}$ then heat of atomiza-
tion of hydrogen is
(1) 52 keal
(2) $104 \mathrm{kcal}$
(3) $208 \mathrm{kcal}$
(4) None of these

Mishal Gul

Numerade Educator

Problem 32

IIeat of combustion of $\mathrm{CII}_{4}, \mathrm{C}_{2} \mathrm{II}_{4}$ and $\mathrm{C}_{2} \mathrm{II}_{6}$ are 890 , 1411 and $1560 \mathrm{~kJ} / \mathrm{mol}$, respectively. Which has the lowest calorific fucl value in $\mathrm{kJ} / \mathrm{g}$ ?
(1) $\mathrm{CH}_{4}$
(2) $\mathrm{C}_{2} \mathrm{H}_{4}$
(3) $\mathrm{C}_{2} \mathrm{H}_{6}$
(4) All

Mishal Gul

Numerade Educator

Problem 33

The standard heats of formation of $\mathrm{NO}_{2(\mathrm{~g})}$ and $\mathrm{N}_{2} \mathrm{O}_{4}(\mathrm{~g})$ are $8.0$ and $2.0 \mathrm{kcal} \mathrm{mol}^{-1}$, respectively. The
heat of dimcrization of $\mathrm{NO}_{2}$ in kcal is
(1) $10.0$
(2) $6.0$
(3) $12.0$
(4) $14.0$

Mishal Gul

Numerade Educator

Problem 34

$\mathrm{II}_{2}(\mathrm{~g})+\frac{1}{2} \mathrm{O}_{2}(\mathrm{~g}) \rightarrow \mathrm{II}_{2} \mathrm{O}(1) ; \Delta H_{29 \times \mathrm{K}}=68.32 \mathrm{kcal} .$
Heat of vapourisation of water at I atm and $25^{\circ} \mathrm{C}$ is $10.52$ kcal. The standard heat of formation (in kcal) of 1 mole of water vapour at $25^{\circ} \mathrm{C}$ is
(1) $-78.84$
(2) $78.84$
(3) $+57.8$
(4) $-57.8$

Mishal Gul

Numerade Educator

Problem 35

According to the equation $\mathrm{C}_{6} \mathrm{H}_{6}(1)+\frac{15}{2} \mathrm{O}_{2}(\mathrm{~g}) \rightarrow$
$6 \mathrm{CO}_{2}(\mathrm{~g})+3 \mathrm{H}_{2} \mathrm{O}(\mathrm{l}), \Delta / /=-3264.4 \mathrm{~kJ} / \mathrm{mol}$, the energy
evolved when $7.8 \mathrm{~g}$ of benzene is burnt in air will be
(1) $163.32 \mathrm{~kJ} / \mathrm{mol}$
(2) $326.4 \mathrm{~kJ} / \mathrm{mol}$
(3) $32.64 \mathrm{~kJ} / \mathrm{mol}$
(4) $3.264 \mathrm{~kJ} / \mathrm{mol}$

Mishal Gul

Numerade Educator

Problem 36

Given that standard heat enthalpy of $\mathrm{CII}_{4}, \mathrm{C}_{2} \mathrm{II}_{4}$ and $\mathrm{C}_{3} \mathrm{I} \mathrm{I}_{8}$ are $17.9,12.5$ and $24.8 \mathrm{kca} 1 / \mathrm{mol}$, respective-
ly. The $\Delta H$ for the reaction $\mathrm{CII}_{4}+\mathrm{C}_{2} \mathrm{II}_{4} \rightarrow \mathrm{C}_{3} \mathrm{I} \mathrm{I}_{8}$ is
(1) $55.2 \mathrm{kcal}$
(2) $30.2 \mathrm{kcal}$
(3) $55.2 \mathrm{kcal}$
(4) $19.4$

Mishal Gul

Numerade Educator

Problem 37

In which case of mixing of a strong acid and a strong base each of $1 \mathrm{~N}$ concentration, temperature increase is highest in(1) $20 \mathrm{~mL}$ acid $-30 \mathrm{~mL}$ alkali
(2) $10 \mathrm{~mL}$ acid $-40 \mathrm{~mL}$ alkali
(3) $25 \mathrm{~mL}$ acid $-25 \mathrm{~mL}$ alkali
(4) $35 \mathrm{~mL}$ acid $-15 \mathrm{~mL}$ alkali

Mishal Gul

Numerade Educator

Problem 38

$2.1 \mathrm{~g}$ of Fe combines with S cvolving $3.77 \mathrm{~kJ}$. The heat of formation of FeS in $\mathrm{kJ} / \mathrm{mol}$ is
(1) $3.77$
(2) $1.78$
(3) $100.5$
(4) Nonc

Mishal Gul

Numerade Educator

Problem 39

The heat cvolved during the combustion of 112 litre of water gas (mixture of equal volumes of $\mathrm{II}_{2}$ and $(\mathrm{CO})$ is
(i) $\mathrm{H}_{2}(\mathrm{~g})+\frac{1}{2} \mathrm{O}_{2}(\mathrm{~g}) \rightarrow \mathrm{H}_{2} \mathrm{O}(\mathrm{g}) ; \Delta / l=-241.8 \mathrm{k} \mathrm{J}$
(ii) $\mathrm{CO}(\mathrm{g})+\frac{1}{2} \mathrm{O}_{2}(\mathrm{~g}) \rightarrow \mathrm{CO}_{2}(\mathrm{~g}) ; \Delta H=283 \mathrm{~kJ}$
(1) $241.8 \mathrm{~kJ}$
(2) $283.3 \mathrm{~kJ}$
(3) $1312 \mathrm{~kJ}$
(4) $1586 \mathrm{~kJ}$

Mishal Gul

Numerade Educator

Problem 40

A person requires 2870 kcal of energy to lead a normal daily life. If heat of combustion of cane sugar is $-1349$ kcal, then his daily consumption of sugar is
(1) $728 \mathrm{~g}$
(2) $0.728 \mathrm{~g}$
(3) $342 \mathrm{~g}$
(4) $0.342 \mathrm{~g}$

Mishal Gul

Numerade Educator

Problem 41

Equal volumes of $1 \mathrm{M} \mathrm{HCl}$ and $1 \mathrm{M} \mathrm{H}_{2} \mathrm{SO}_{4}$ are
neutralized by dilute $\mathrm{NaOH}$ solution and $\mathrm{X}$ and $\mathrm{Y}$ kcal of heat are liberated, respectively. Which of the following is true?
(1) $\mathrm{X}=\mathrm{Y}$
(2) $\mathrm{X}=0.5 \mathrm{Y}$
(3) $\mathrm{X}=0.4 \mathrm{Y}$
(4) None

Mishal Gul

Numerade Educator

Problem 42

To a solution of $500 \mathrm{~mL}$ of $\mathrm{KOII}$ is added $50 \mathrm{~mL}$ of $2 \mathrm{M}$ IICl and the mixture is well shaken. The risc in tempcrature $T_{1}$ is noted. The cxperiment is then repcated using $250 \mathrm{~mL}$ of cach solution and rise in temperature $T_{2}$ is again noted. $\Lambda$ ssume all heat is taken up by the solution. Now, which of the following is correct?
(1) $T_{1}=T_{2}$.
(2) $T_{1}$ is twice as larger as $T_{2}$.
(3) $T_{2}$ is twice as larger as $T_{1}$.
(4) $T_{1}$ is 4 times as larger as $T_{2}$.

Mishal Gul

Numerade Educator

Problem 43

Under the same conditions, how many $\mathrm{mL}$ of $1 \mathrm{M}$ KOII and $0.5 \mathrm{M} \mathrm{II}_{2} \mathrm{SO}_{4}$ solutions respectively when mixed for a total volume of $100 \mathrm{~mL}$ produce the highest rise in temperature?
(1) $67: 33$
(2) $33: 67$
(3) $40: 60$
(4) $50: 50$

Mishal Gul

Numerade Educator

Problem 44

The enthalpy of combustions at $25^{\circ} \mathrm{C}$ of $\mathrm{II}_{2}$, cyclohexene $\left(\mathrm{C}_{6} \mathrm{II}_{10}\right)$ and cyclohexane $\left(\mathrm{C}_{6} \mathrm{II}_{12}\right)$ arc 241 , 3800 and $3920 \mathrm{~kJ} / \mathrm{mol}$, respectively. The heat of hydrogenation of cyclohexane is(1) $-121 \mathrm{~kJ} / \mathrm{mole}$
$(2)+121 \mathrm{~kJ} / \mathrm{mole}$
(3) $-242 \mathrm{~kJ} / \mathrm{mole}$
(4) $+242 \mathrm{~kJ} / \mathrm{mol}$

Mishal Gul

Numerade Educator

Problem 45

The heat of ncutralization of a strong basc and a strong acid is $57.0 \mathrm{~kJ}$. The heat released when $0.5$ mole of $\mathrm{IINO}_{3}$ solution is added to $0.20$ moles of NaOII solution is
(1) $11.40 \mathrm{~kJ}$
(2) $57.0 \mathrm{~kJ}$
(3) $28.5 \mathrm{~kJ}$
(4) $34.9 \mathrm{~kJ}$

Mishal Gul

Numerade Educator

Problem 46

The heat change in a reaction does not depend upon the
(1) Conditions of $P$ or $V$ under which a reaction is carried out.
(2) Initial and final cnthalpics of the reactants and products.
(3) State of reactants and products.
(4) Number of intermediate stages involved.

Mishal Gul

Numerade Educator

Problem 47

For the reactions, where experimental determination of cnthalpy is not possible the enthalpy can be calculated by
(1) Kirchoff's law
(2) Hess's law
(3) Henry's law
(4) Clapeyron equation

Mishal Gul

Numerade Educator

Problem 48

Hess's law of heat summation is an application of
(1) Entropy
(2) Kirchoff's law
(3) First law of thermodynamics
(4) Sccond law of thermodynamics

Mishal Gul

Numerade Educator

Problem 49

Hess's law is used in the determination of
(1) Heat of formation
(2) Heat of reaction
(3) Heat of transition
(4) All of these

Mishal Gul

Numerade Educator

Problem 50

$\Lambda$ hypothctical reaction $\Lambda \longrightarrow \mathrm{B}$ procecds via following sequence of steps.
(i) $\mathrm{A} \longrightarrow \mathrm{C} ; \Delta / I=\mathrm{q}_{1}$
(ii) $\mathbf{C} \longrightarrow \mathrm{D} ; \Delta / I=\mathrm{q}_{2}$
(iii) $\frac{1}{2} \mathrm{D} \longrightarrow \mathrm{B} ; \Delta H=\mathrm{q}_{3}$
The heat of reaction is
(1) $q_{1}-q_{2}+2 q_{3}$
(2) $\mathrm{q}_{1}+\mathrm{q}_{2}-2 \mathrm{q}_{3}$
(3) $\mathrm{a}_{1}+\mathrm{c}_{3}+2 \mathrm{q}$
(4) $\mathrm{a}_{1}+2 \mathrm{q}_{2}+2 \mathrm{q}_{2}$

Mishal Gul

Numerade Educator

Problem 51

IIcss's law of heat summation is
(1) Law of conservation of cnergy
(2) Really another way of stating that cnergy can ncither be created nor destroyed
(3) IIclpful in calculating heat of reaction which are impossible in practice
(4) \Lambdall the above

Mishal Gul

Numerade Educator

Problem 52

Heat of transition is the heat evolved or absorbed when a substance is converted from
(1) solid to liquid
(2) solid to vapour
(3) liquid to vapour
(4) onc allotropic form to another allotropic form

Mishal Gul

Numerade Educator

Problem 53

$C_{\text {(dianemd) }}+\mathrm{O}_{2}(\mathrm{~g}) \rightarrow \mathrm{CO}_{2}(\mathrm{~g}) ; \Delta H=395 \mathrm{~kJ}$
$C_{\text {(Braphite) }}+\mathrm{O}_{2}(\mathrm{~g}) \rightarrow \mathrm{CO}_{2}(\mathrm{~g}) ; \Delta / I=-393.5 \mathrm{~kJ}$
The $\Delta / /$ when diamond is formed from graphite
(1) $-1.5 \mathrm{~kJ}$
$(2)+1.5 \mathrm{~kJ}$
(3) $+3.0 \mathrm{k} \mathrm{J}$
(4) $-3.0 \mathrm{~kJ}$

Mishal Gul

Numerade Educator

Problem 54

$\mathrm{H}_{2}+\frac{1}{2} \mathrm{O}_{2} \longrightarrow \mathrm{H}_{2} \mathrm{O} ; \Delta l I=-68.39 \mathrm{kcal}$
$\mathrm{K}+\mathrm{aq} \longrightarrow \mathrm{KOH}(\mathrm{aq})+\frac{1}{2} \mathrm{H}_{2}(\mathrm{~g}) ; \Delta / I=-48 \mathrm{kca} 1$
$\mathrm{KOII}+\mathrm{aq} \longrightarrow \mathrm{KOHI}(\mathrm{aq}) ; \Delta H=14 \mathrm{kcal}$
The heat of formation (in kcal) of KOII is
(1) $-68.3948-14$
(2) $-68.39-48+14$
(3) $68.39-48+14$
(4) $68.39+48+14$

Mishal Gul

Numerade Educator

Problem 54

$\mathrm{H}_{2}+\frac{1}{2} \mathrm{O}_{2} \longrightarrow \mathrm{H}_{2} \mathrm{O} ; \Delta / I=-68.39 \mathrm{kcal}$
$\mathrm{K}+\mathrm{aq} \longrightarrow \mathrm{KOH}(\mathrm{aq})+\frac{1}{2} \mathrm{H}_{2}(\mathrm{~g}) ; \Delta / /=-48 \mathrm{kca} 1$
$\mathrm{KOH}+\mathrm{aq} \longrightarrow \mathrm{KOH}(\mathrm{aq}) ; \Delta H=14 \mathrm{kcal}$
The heat of formation (in $\mathrm{kcal}$ ) of KOII is
(1) $-68.3948-14$
(2) $-68.39-48+14$
(3) $68.39-48+14$
(4) $68.39+48+14$

Mishal Gul

Numerade Educator

Problem 55

\begin{aligned}
&\text { If } \mathrm{S}+\mathrm{O}_{2} \longrightarrow \mathrm{SO}_{2} ; \Delta H=298.2 \mathrm{~kJ} \\
&\mathrm{SO}_{2}+\frac{1}{2} \mathrm{O}_{2} \longrightarrow \mathrm{SO}_{3} ; \Delta l l=-98.7 \mathrm{~kJ} \\
&\mathrm{SO}_{3}+\mathrm{H}_{2} \mathrm{O} \longrightarrow \mathrm{H}_{2} \mathrm{SO}_{4} ; \Delta / I=-130.2 \mathrm{~kJ} \\
&\mathrm{II}_{2}+\frac{1}{2} \mathrm{O}_{2} \longrightarrow \mathrm{II}_{2} \mathrm{O} ; \Delta H=227.3 \mathrm{~kJ}
\end{aligned}The enthalpy of formation of $\mathrm{H}_{2} \mathrm{SO}_{4}$ at $298 \mathrm{~K}$ will be
(1) $-813.9 \mathrm{~kJ} \quad(2)+320.5 \mathrm{~kJ}$
(3) $-650.3 \mathrm{k}$ ]
(4) $-433.7 \mathrm{~kJ}$

Mishal Gul

Numerade Educator

Problem 56

From the following data, the heat of formation of $\mathrm{Ca}(\mathrm{OII})_{2}(\mathrm{~s})$ at $18^{\circ} \mathrm{C}$ is $\ldots . . \mathrm{kcal} .$
$\Delta / l_{18{ }^{\circ} \mathrm{c}}=-15.26 \mathrm{kcal}$
$\mathrm{II}_{2} \mathrm{O}(\mathrm{l})+\mathrm{II}_{2}(\mathrm{~g})+\frac{1}{2} \mathrm{O}_{2}(\mathrm{~g}) ; \Delta H_{18 \mathrm{C}}=68.37 \mathrm{kcal}$
$\mathrm{Ca}(\mathrm{s})+\frac{1}{2} \mathrm{O}_{2}(\mathrm{~g}) \stackrel{2}{\longrightarrow} \mathrm{CaO}(\mathrm{s}) ; \Delta / I_{18^{\circ} \mathrm{C}}=-151.8 \mathrm{keal}$
(1) $-98.69$
(2) $-235.43$
(3) $194.91$
(4) $98.69$

Mishal Gul

Numerade Educator

Problem 57

$C_{\text {(graphite) }}+\mathrm{O}_{2}(\mathrm{~g}) \longrightarrow \mathrm{CO}_{2}(\mathrm{~g}) ; \Delta H=94.05 \mathrm{kcal}$
$\mathrm{mol}^{-1}$
$\left.C_{\text {(dianwed })}+\mathbf{O}_{2}{ }_{\mathbf{t}} \mathrm{g}\right) \longrightarrow \mathrm{CO}_{2}(\mathrm{~g}) ; \Delta H=94.50 \mathrm{kcal}$
Therefore,
(1) $\mathbf{C}_{\text {(diamond) }} \rightarrow C_{\text {tgraphite }} ; \Delta I I_{298 \mathrm{~K}}^{\gamma}=-450$ cal mol 1
(2) $\mathbf{C}_{(\text {graptile) }} \rightarrow \mathrm{C}_{\text {idiannond }} ; \Delta / I_{2 v \mathrm{~K}}^{\theta}=-450 \mathrm{cal} \mathrm{mol}$
(3) Diamond is harder than graphitc.
(4) Graphite is stable isotope.

Mishal Gul

Numerade Educator

Problem 58

If $\mathrm{H}_{2}(\mathrm{~g})+\mathrm{Cl}_{2}(\mathrm{~g}) \longrightarrow 2 \mathrm{HCl} ; \Delta \mathrm{H}^{\circ}=-44 \mathrm{k} \mathrm{cal}$
2Na(s) $12 \mathrm{IICl}(\mathrm{g}) \longrightarrow 2 \mathrm{NaCl}(\mathrm{s})+\mathrm{II}_{2}(\mathrm{~g})$
$\Delta H=152 \mathrm{kcal}$
Then, $\mathrm{Na}(\mathrm{s})+0.5 \mathrm{Cl}_{2}(\mathrm{~g}) \longrightarrow \mathrm{NaCl}(\mathrm{s}) ; \Delta H^{\circ}=$ ?
(1) $108 \mathrm{kcal}$
(2) 196 kcal
(3) $-98 \mathrm{kcal}$
(4) $54 \mathrm{kcal}$

Mishal Gul

Numerade Educator

Problem 59

$\mathrm{f} \mathrm{C}(\mathrm{s})+\frac{1}{2} \mathrm{O}_{2}(\mathrm{~g}) \rightarrow \mathrm{CO}_{2}(\mathrm{~g}) ; \Delta H=\mathrm{S}$
$\mathrm{C}(\mathrm{s})+\mathrm{O}_{2}(\mathrm{~g}) \rightarrow \mathrm{CO}_{2}(\mathrm{~g}) ; \Delta / I=\mathrm{R}$
Then, the heat of formation of CO
(1) $\mathrm{R}+\mathrm{S}$
(2) $\mathrm{R} \mathrm{S}$
(3) $\mathrm{S} \quad \mathrm{R}$
(4) $\mathrm{R} \times \mathrm{S}$

Mishal Gul

Numerade Educator

Problem 60

Given the bond energies of $\mathrm{N} \equiv \mathrm{N}, \mathrm{H}-\mathrm{H}$ and $\mathrm{N}-\mathrm{H}$
bonds as 945,436 and $391 \mathrm{~kJ}$ mol $^{1}$, respectively, the enthalpy of the reaction $\mathrm{N}_{2}(\mathrm{~g})+3 \mathrm{H}_{2}(\mathrm{~g}) \rightarrow 2 \mathrm{NH}_{3}(\mathrm{~g})$ is
(1) $-93 \mathrm{~kJ}$
(2) $102 \mathrm{~kJ}$
(3) $90 \mathrm{~kJ}$
(4) $105 \mathrm{~kJ}$

Mishal Gul

Numerade Educator

Problem 61

Bond cnergics of $(1] \quad I I),(O=O)$ and $(O \quad$ II $)$ are 105,120 and $220 \mathrm{kcal} / \mathrm{mol}$, respectively, then $\Delta$ in the rcaction is cqual to $2 \mathrm{H}_{2}(\mathrm{~g})+\mathrm{O}_{2}(\mathrm{~g}) \longrightarrow 2 \mathrm{H}_{2} \mathrm{O}(1)$
$\begin{array}{ll}\text { (1) }-115 & \text { (2) }-130\end{array}$
(3) $-118$
(4) $-550$

Mishal Gul

Numerade Educator

Problem 62

For the changc $\mathrm{C}_{\text {diamand }} \longrightarrow C_{\text {graphite }}, \Delta H=1.89 \mathrm{~kJ}$ If $6 \mathrm{~g}$ of diamond and $6 \mathrm{~g}$ of graphite are scparatcly burnt to yicld $\mathrm{CO}_{2}$ the hcat liberated in the first case is(1) less than in the second case by $1.89 \mathrm{~kJ}$
(2) less than in the second case by $11.34 \mathrm{k}$.
(3) less than in the second case by $14.34 \mathrm{k}$.]
(4) more than in the second case by $0.945 \mathrm{~kJ}$

Mishal Gul

Numerade Educator

Problem 63

Given $\mathrm{NII}_{3}(\mathrm{~g})+3 \mathrm{Cl}_{2}(\mathrm{~g}) \rightleftharpoons \mathrm{NCl}_{3}(\mathrm{~g})+3$ IICl $(\mathrm{g}) ; \mathrm{II}_{1}$
$\mathrm{N}_{2}(\mathrm{~g})+3 \mathrm{H}_{2}(\mathrm{~g}) \rightleftharpoons 2 \mathrm{NH}_{3}(\mathrm{~g}) ; \mathrm{H}_{2}$
$\mathrm{II}_{2}(\mathrm{~g})+\mathrm{Cl}_{2}(\mathrm{~g}) \rightleftharpoons 2 \mathrm{IICl} ; \mathrm{II}_{3}$
The heat of formation of $\mathrm{NCl}_{3}(g)$ in the terms of $\Delta l l_{1}$ $\Delta l I_{2}$ and $\Delta / I_{3}$ is
(1) $\Delta H_{f}=\Delta H_{1}+\frac{\Delta / I_{2}}{2}-\frac{3}{2} \Delta H_{3}$
(2) $\Delta / I_{\mathrm{f}}=\Delta / I_{1}+\frac{\Delta H_{2}}{2}-\frac{3}{2} \Delta l l_{3}$
(3) $\Delta H_{f}=\Delta H_{1}+\frac{\Delta l I_{2}}{2}-\frac{3}{2} \Delta H_{3}$
(4) None

Mishal Gul

Numerade Educator

Problem 64

On the basis of the thermochemical equations $\mathrm{H}_{2} \mathrm{O}(\mathrm{g})+\mathrm{C}(\mathrm{s}) \longrightarrow \mathrm{CO}(\mathrm{g}) \Delta \|=13 \mathrm{l} \mathrm{kJ}$
$\mathrm{CO}(\mathrm{g})+\frac{1}{2} \mathrm{O}_{2}(\mathrm{~g}) \longrightarrow \mathrm{CO}_{2}(\mathrm{~g}) \Delta H=282 \mathrm{~kJ}$
$\mathrm{H}_{2}(\mathrm{~g})+\frac{1}{2} \mathrm{O}_{2}(\mathrm{~g}) \longrightarrow \mathrm{H}_{2} \mathrm{O}(\mathrm{g}) \Delta / I=-242 \mathrm{~kJ}$
$\mathrm{C}(\mathrm{s})+\mathrm{O}_{2}(\mathrm{~g}) \longrightarrow \mathrm{CO}_{2}(\mathrm{~g}) \Delta / /=\mathrm{X} \mathrm{kJ}$
The valuc of $\mathrm{X}$ will be
(1) $393 \mathrm{~kJ}$
(2) $655 \mathrm{~kJ}$
(3) $393 \mathrm{~kJ}$
(4) $655 \mathrm{~kJ}$

Mishal Gul

Numerade Educator

Problem 65

Given that $\mathrm{CII}_{3} \mathrm{CIIO}+\frac{5}{2} \mathrm{O}_{2} \rightarrow 2 \mathrm{CO}_{2}+2 \mathrm{II}_{2} \mathrm{O} ; \Delta H=$
$1168 \mathrm{~kJ} / \mathrm{molc} ; \mathrm{CII}_{3} \mathrm{COOII}+2 \mathrm{O}_{2} \longrightarrow 2 \mathrm{CO}_{2}$
$+2 \mathrm{II}_{2} \mathrm{O} ; \Delta H=876 \mathrm{~kJ} / \mathrm{mole} . \Delta H$ for the reaction
$\mathrm{CII}_{3} \mathrm{CIIO}+\frac{1}{2} \mathrm{O}_{2} \longrightarrow \mathrm{CII}_{3} \mathrm{COOII}$ is
(1) $292 \mathrm{~kJ} / \mathrm{molc}$
(2) $378 \mathrm{~kJ} / \mathrm{molc}$
(3) $195 \mathrm{~kJ} / \mathrm{molc}$
(4) $2044 \mathrm{~kJ} / \mathrm{molc}$

Mishal Gul

Numerade Educator

Problem 66

From the following data, the heat of formation of $\mathrm{PCl}_{5}$ $2 \mathrm{P}(\mathrm{s})+3 \mathrm{Cl}_{2}(\mathrm{~g}) \rightarrow 2 \mathrm{PCl}_{3}(\mathrm{~g}) ; \Delta H=151.8 \mathrm{kcal}$
$\mathrm{PCl}_{3}+\mathrm{Cl}_{2}(\mathrm{~g}) \rightarrow \mathrm{PCl}_{5}(\mathrm{~g}) ; \Delta H=32.8 \mathrm{kcal}$
(1) $217.4 \mathrm{kcal}$
(2) $+217.4 \mathrm{kcal}$
(3) $108.7 \mathrm{kcal}$
(4) $+108.7 \mathrm{kcal}$

Mishal Gul

Numerade Educator