Chemical Thermodynamics · JEE Main previous year questions

Consider the reaction $2{\mathrm{H}}_2\mathrm{S}(\mathrm{g})+3{\mathrm{O}}_2(\mathrm{g})\to 2{\mathrm{H}}_2\mathrm{O}(\mathrm{l})+2\mathrm{S}{\mathrm{O}}_2(\mathrm{g})$ The magnitude of enthalpy change for the reaction in $\mathrm{kJ}\mathrm{mo}{\mathrm{l}}^{-1}$ is ____. (Nearest integer) Given : $${\Delta }_{\mathrm{f}}{\mathrm{H}}^{\ominus }({\mathrm{H}}_2\mathrm{S})=-20.1\mathrm{kJ}\mathrm{mo}{\mathrm{l}}^{-1}$$ $${\Delta }_{\mathrm{f}}{\mathrm{H}}^{\ominus }({\mathrm{H}}_2\mathrm{O})=-286.0\mathrm{kJ}\mathrm{mo}{\mathrm{l}}^{-1}$$ $${\Delta }_{\mathrm{f}}{\mathrm{H}}^{\ominus }(\mathrm{S}{\mathrm{O}}_2)=-297.0\mathrm{kJ}\mathrm{mo}{\mathrm{l}}^{-1}$$

Arrange the following isothermal processes in order of the magnitude of the work $(\mathrm{p}-\mathrm{V})$ involved between states 1 and 2. A. Expansion in single stage ${\mathrm{w}}_{\mathrm{A}}$ B. Expansion in multi stages ${\mathrm{w}}_{\mathrm{B}}$ C. Compression in single stage ${\mathrm{w}}_{\mathrm{C}}$ D. Compression in multi stages ${\mathrm{w}}_{\mathrm{D}}$ Choose the correct option.

1. A.$|{\mathrm{w}}_{\mathrm{B}}|>|{\mathrm{w}}_{\mathrm{A}}|>|{\mathrm{w}}_{\mathrm{C}}|>|{\mathrm{w}}_{\mathrm{D}}|$
2. B.$|{\mathrm{w}}_{\mathrm{C}}|>|{\mathrm{w}}_{\mathrm{D}}|>|{\mathrm{w}}_{\mathrm{A}}|>|{\mathrm{w}}_{\mathrm{B}}|$
3. C.$|{\mathrm{w}}_{\mathrm{C}}|>|{\mathrm{w}}_{\mathrm{D}}|>|{\mathrm{w}}_{\mathrm{B}}|>|{\mathrm{w}}_{\mathrm{A}}|$
4. D.$|{\mathrm{w}}_{\mathrm{B}}|>|{\mathrm{w}}_{\mathrm{A}}|>|{\mathrm{w}}_{\mathrm{D}}|>|{\mathrm{w}}_{\mathrm{C}}|$

Match List - I with List - II. Given $V_1$ and $V_2$ are initial and final volumes respectively. List - I (Isothermal process) A. Reversible expansion B. Free expansion C. Irreversible Compression D. Cyclic reversible List - II (Expression) I. $q=0$ II. $q=nRT\ln \frac{V_2}{V_1}$ III. $w=-P_{\text{ext}}(V_1-V_2)$ IV. $\frac{q_{\text{rev}}}{T}=0$ Choose the correct answer from the options given below :

1. A.A-II, B-III, C-I, D-IV
2. B.A-II, B-I, C-IV, D-III
3. C.A-II, B-I, C-III, D-IV
4. D.A-I, B-II, C-III, D-IV

The correct order of first (${\Delta }_i{\text{H}}_1$) and second (${\Delta }_i{\text{H}}_2$) ionisation enthalpy values of Cr and Mn are : A. ${\Delta }_i{\text{H}}_1:\text{Cr}>\text{Mn}$ B. ${\Delta }_i{\text{H}}_2:\text{Cr}>\text{Mn}$ C. ${\Delta }_i{\text{H}}_1:\text{Mn}>\text{Cr}$ D. ${\Delta }_i{\text{H}}_2:\text{Mn}>\text{Cr}$ Choose the correct answer from the options given below :

1. A.A and B only
2. B.B and C only
3. C.A and D only
4. D.C and D only

The $1^{\mathrm{st}}$ ionization enthalpy for $\mathrm{Mg}$ is $+737kJ/mol$. The most probable estimated value of the $2^{\mathrm{nd}}$ ionization enthalpy of $\mathrm{Mg}$ is ____.

1. A.$-906kJ/mol$
2. B.$-856kJ/mol$
3. C.$+1450kJ/mol$
4. D.$+590kJ/mol$

If $3.365\mathrm{g}$ of ethanol ($l$) is burnt completely in a bomb calorimeter at $298.15\mathrm{K}$, the heat produced is $99.472\mathrm{kJ}$. The $|\Delta {\mathrm{H}}_{\mathrm{f}}^{\circ }|$ of ethanol at $298.15\mathrm{K}$ is ____ $\times 10^2\mathrm{kJ}\mathrm{mo}{\mathrm{l}}^{-1}$. (Nearest integer) Given: Standard enthalpy for combustion of graphite $=-393.5\mathrm{kJ}\mathrm{mo}{\mathrm{l}}^{-1}$ Standard enthalpy of formation of water (l) $=-285.8\mathrm{kJ}\mathrm{mo}{\mathrm{l}}^{-1}$ Molar mass in $\mathrm{g}\mathrm{mo}{\mathrm{l}}^{-1}$ of C, H, O are 12 , 1 and 16 respectively

Consider the following data. (i) $2Al(\mathrm{s})+6HCl(\mathrm{aq})\to \mathrm{A}{\mathrm{l}}_2\mathrm{C}{\mathrm{l}}_6(\mathrm{aq})+3{\mathrm{H}}_2(\mathrm{g})+1200kJ/mol$ (ii) ${\mathrm{H}}_2(\mathrm{g})+\mathrm{C}{\mathrm{l}}_2(\mathrm{g})\to 2HCl(\mathrm{g})+164kJ/mol.$ (iii) $\mathrm{HCl}(\mathrm{g})+\mathrm{aq}\to \mathrm{HCl}(\mathrm{aq})+83kJ/mol.$ (iv) $\mathrm{A}{\mathrm{l}}_2\mathrm{C}{\mathrm{l}}_6(\mathrm{s})+\mathrm{aq}\to \mathrm{A}{\mathrm{l}}_2\mathrm{C}{\mathrm{l}}_6(\mathrm{aq})+663kJ/mol$ The enthalpy of formation of anhydrous solid $\mathrm{A}{\mathrm{l}}_2\mathrm{C}{\mathrm{l}}_6$ is :

1. A.$-648\mathrm{kJ}\mathrm{mo}{\mathrm{l}}^{-1}$
2. B.$-1350\mathrm{kJ}\mathrm{mo}{\mathrm{l}}^{-1}$
3. C.$-2002\mathrm{kJ}\mathrm{mo}{\mathrm{l}}^{-1}$
4. D.$-1527\mathrm{kJ}\mathrm{mo}{\mathrm{l}}^{-1}$

Given below are two statements : Statement (I) : The first ionisation enthalpy of the elements Na, Mg, Cl and Ar follows the order $$\mathrm{Na}>\mathrm{Mg}>\mathrm{Cl}>Ar.$$ Statement (II) : Among Ca, Al, Fe and B, the third ionisation enthalpy is very high for Ca. In the light of the above statements, choose the correct answer from the options given below :

1. A.Both Statement I and Statement II are true
2. B.Both Statement I and Statement II are false
3. C.Statement I is true but Statement II is false
4. D.Statement I is false but Statement II is true

Gas 'A' undergoes change from state 'X' to state 'Y'. In this process, the heat absorbed and work done by the gas is $10\mathrm{J}$ and $18\mathrm{J}$ respectively. Now gas is brought back to state 'X' by another process during which $6\mathrm{J}$ of heat is evolved. In the reverse process of 'Y' to 'X',

1. A.$18\mathrm{J}$ of the work is done by the gas 'A'.
2. B.$2\mathrm{J}$ of the work is done by the gas 'A'.
3. C.$12\mathrm{J}$ of the work is done on the gas 'A' by the surrounding.
4. D.$14\mathrm{J}$ of the work is done on the gas 'A' by the surrounding.

Given below are two statements : Statement I : The second ionization enthalpy of B, Al and Ga is in the order of $\mathrm{B}>\mathrm{Al}>\mathrm{Ga}$. Statement II : The correct order in terms of first ionization enthalpy is $\mathrm{Si}<\mathrm{Ge}<\mathrm{Pb}<\mathrm{Sn}$. In the light of the above statements, choose the correct answer from the options given below :

1. A.Both Statement I and Statement II are true
2. B.Both Statement I and Statement II are false
3. C.Statement I is true but Statement II is false
4. D.Statement I is false but Statement II is true

Among $\mathrm{F}{\mathrm{e}}^{2+}$, $\mathrm{F}{\mathrm{e}}^{3+}$, $\mathrm{C}{\mathrm{r}}^{2+}$ and $\mathrm{Z}{\mathrm{n}}^{2+}$, the ion that shows positive borax bead test and with highest ionisation enthalpy is :

1. A.$\mathrm{F}{\mathrm{e}}^{2+}$
2. B.$\mathrm{Z}{\mathrm{n}}^{2+}$
3. C.$\mathrm{C}{\mathrm{r}}^{2+}$
4. D.$\mathrm{F}{\mathrm{e}}^{3+}$

Match the LIST-I with LIST-II $$\begin{array}{llll}\text{List-I Isothermal process for ideal gas system}& & \text{List-II Work done ( }{V}_f>V_i\text{ )}& \\ \text{A.}& \text{Reversible expansion}& \text{I.}& w=0\\ \text{B.}& \text{Free expansion}& \text{II.}& w=-nRT\ln \left(\frac{V_f}{V_i}\right)\\ \text{C.}& \text{Irreversible expansion}& \text{III.}& w=-p_{\mathrm{ex}}(V_f-V_i)\\ \text{D.}& \text{Irreversible compression}& \text{IV.}& w=-p_{\mathrm{ex}}(V_i-V_f)\end{array}$$ Choose the correct answer from the options given below:

1. A.A-IV, B-I, C-III, D-II
2. B.A-I, B-III, C-II, D-IV
3. C.A-II, B-I, C-III, D-IV
4. D.A-IV, B-II, C-III, D-I

1. A.
2. B.
3. C.
4. D.

Match the LIST-I with LIST-II $$\begin{array}{ll}\text{List-I Thermodynamic Process}& \text{List-II Magnitude in kJ}\\ \text{A. Work done in reversible, isothermal expansion of }2\text{ mol of ideal gas from }2\mathrm{d}{\mathrm{m}}^3\text{ to }20\mathrm{d}{\mathrm{m}}^3\text{ at }300\mathrm{K}.& \text{I. }4\\ \text{B. Work done in irreversible isothermal expansion of }1\text{ mol ideal gas from }1{\mathrm{m}}^3\text{ to }3{\mathrm{m}}^3\text{ at }300\mathrm{K}\text{ against a constant pressure of }3\mathrm{kPa}.& \text{II. }11.5\\ \text{C. Change in internal energy for adiabatic expansion of a }1\text{ mol ideal gas with change of temperature }=320\mathrm{K}\text{ and }{\overline{C}}_V=\frac{3}{2}R.& \text{III. }6\\ \text{D. Change in enthalpy at constant pressure of }1\text{ mol ideal gas with change of temperature }=337\mathrm{K}\text{ and }{\overline{C}}_p=\frac{5}{2}R.& \text{IV. }7\end{array}$$

1. A.A-I, B-II, C-III, D-IV
2. B.A-III, B-II, C-IV, D-I
3. C.A-II, B-I, C-III, D-IV
4. D.A-II, B-III, C-I, D-IV

1. A.
2. B.
3. C.
4. D.

Given below are two statements : Statement I : The correct order in terms of bond dissociation enthalpy is $\mathrm{C}{\mathrm{l}}_2>\mathrm{B}{\mathrm{r}}_2>{\mathrm{F}}_2>{\mathrm{I}}_2$. Statement II : The correct trend in the covalent character of the metal halides is $[\mathrm{SnC}{\mathrm{l}}_4>\mathrm{SnC}{\mathrm{l}}_2]$, $[\mathrm{PbC}{\mathrm{l}}_4>\mathrm{PbC}{\mathrm{l}}_2]$ and $[\mathrm{U}{\mathrm{F}}_4>\mathrm{U}{\mathrm{F}}_6]$. In the light of the above statements, choose the correct answer from the options given below :

1. A.Both Statement I and Statement II are true
2. B.Both Statement I and Statement II are false
3. C.Statement I is false but Statement II is true
4. D.Statement I is true but Statement II is false

The atomic number of the element from the following with lowest $1^{\mathrm{st}}$ ionisation enthalpy is :

1. A.$32$
2. B.$35$
3. C.$19$
4. D.$87$

One mole of an ideal gas expands isothermally and reversibly from $10\mathrm{d}{\mathrm{m}}^3$ to $20\mathrm{d}{\mathrm{m}}^3$ at 300 K . $\Delta \mathrm{U}$, q and work done in the process respectively are Given: $\mathrm{R}=8.3\mathrm{J}{\mathrm{K}}^{-1}\mathrm{mo}{\mathrm{l}}^{-1}$ $\ln 10=2.3$ $\log 2=0.30$ $\log 3=0.48$

1. A.$0,21.84\mathrm{kJ},-1.726\mathrm{J}$
2. B.$0,21.84\mathrm{kJ},21.84\mathrm{kJ}$
3. C.$0,1.718\mathrm{kJ},-1.718\mathrm{kJ}$
4. D.$0,-17.18\mathrm{kJ},1.718\mathrm{J}$

Let us consider a reversible reaction at temperature, T. In this reaction, both $\Delta \mathrm{H}$ and $\Delta \mathrm{S}$ were observed to have positive values. If the equilibrium temperature is Te , then the reaction becomes spontaneous at:

1. A.$\mathrm{Te}>\mathrm{T}$
2. B.$\mathrm{T}>\mathrm{Te}$
3. C.$\mathrm{T}=\mathrm{Te}$
4. D.$\mathrm{Te}=5\mathrm{T}$

Which of the following statements are correct? A. The process of adding an electron to a neutral gaseous atom is always exothermic. B. The process of removing an electron from an isolated gaseous atom is always endothermic. C. The $1^{\text{st}}$ ionization energy of boron is less than that of beryllium. D. The electronegativity of C is 2.5 in $\mathrm{C}{\mathrm{H}}_4$ and $\mathrm{CC}{\mathrm{l}}_4$ E. Li is the most electropositive among elements of group I. Choose the correct answer from the options given below:

1. A.A, C and D Only
2. B.B and C Only
3. C.B and D Only
4. D.B, C and E Only

A sample of $\mathrm{n}$-octane ($1.14\mathrm{g}$) was completely burnt in excess of oxygen in a bomb calorimeter, whose heat capacity is $5{\mathrm{kJ}\mathrm{K}}^{-1}$. As a result of combustion reaction, the temperature of the calorimeter is increased by $5\mathrm{K}$. The magnitude of the heat of combustion of octane at constant volume is__________ ${\mathrm{kJmol}}^{-1}$ (nearest integer).

Arrange the following in order of magnitude of work done by the system/on the system at constant temperature. (a) $|w_{\text{reversible}}|$ for expansion in infinite stages. (b) $|w_{\text{irreversible}}|$ for expansion in single stage. (c) $|w_{\text{reversible}}|$ for compression in infinite stages. (d) $|w_{\text{irreversible}}|$ for compression in single stage. Choose the correct answer from the options given below :

1. A.$d>c=a>b$
2. B.$c=a>d>b$
3. C.$a>c>b>d$
4. D.$a>b>c>d$

$\mathrm{S}(\mathrm{g})+\frac{3}{2}{\mathrm{O}}_2(\mathrm{g})\to \mathrm{S}{\mathrm{O}}_3(\mathrm{g})+2x\text{ kcal}$ $\mathrm{S}{\mathrm{O}}_2(\mathrm{g})+\frac{1}{2}{\mathrm{O}}_2(\mathrm{g})\to \mathrm{S}{\mathrm{O}}_3(\mathrm{g})+y\text{ kcal}$ The heat of formation of $\mathrm{S}{\mathrm{O}}_2(\mathrm{g})$ is given by :

1. A.$2x+y\text{ kcal}$
2. B.$\frac{2x}{y}\text{ kcal}$
3. C.$y-2x\text{ kcal}$
4. D.$x+y\text{ kcal}$