Chemical Thermodynamics · JEE Main previous year questions

2024 11 questions

1. Q632024 · 9 Apr 2024 · Shift 1

   Given below are two statements : Statement (I) : The oxidation state of an element in a particular compound is the charge acquired by its atom on the basis of electron gain enthalpy consideration from other atoms in the molecule. Statement (II) : $\mathrm{p}\pi -\mathrm{p}\pi$ bond formation is more prevalent in second period elements over other periods. In the light of the above statements, choose the most appropriate answer from the options given below :

   1. A.Statement I is correct but Statement II is incorrect
   2. B.Both Statement I and Statement II are correct
   3. C.Statement I is incorrect but Statement II is correct
   4. D.Both Statement I and Statement II are incorrect
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   Answer: C

2. Q822024 · 6 Apr 2024 · Shift 2· Numerical answer

   For the reaction at $298\text{ K}$, $2\text{ A}+\text{B}\to \text{C}$, $\Delta H=400{\text{ kJ mol}}^{-1}$ and $\Delta S=0.2{\text{ kJ mol}}^{-1}{\text{ K}}^{-1}$. The reaction will become spontaneous above ________ $\text{K}$.

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   Answer: 2000

3. Q762024 · 4 Apr 2024 · Shift 1

   The correct order of first ionization enthalpy values of the following elements is : (A) O (B) N (C) Be (D) F (E) B Choose the correct answer from the options given below :

   1. A.$\mathrm{A}<\mathrm{B}<\mathrm{D}<\mathrm{C}<\mathrm{E}$
   2. B.$\mathrm{C}<\mathrm{E}<\mathrm{A}<\mathrm{B}<\mathrm{D}$
   3. C.$\mathrm{E}<\mathrm{C}<\mathrm{A}<\mathrm{B}<\mathrm{D}$
   4. D.$\mathrm{B}<\mathrm{D}<\mathrm{C}<\mathrm{E}<\mathrm{A}$
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   Answer: C

4. Q842024 · 4 Apr 2024 · Shift 1· Numerical answer

   The enthalpy of formation of ethane (${\mathrm{C}}_2{\mathrm{H}}_6$) from ethylene by addition of hydrogen where the bond-energies of $\mathrm{C}-\mathrm{H}$, $\mathrm{C}-\mathrm{C}$, $\mathrm{C}=\mathrm{C}$, $\mathrm{H}-\mathrm{H}$ are $414\mathrm{kJ}$, $347\mathrm{kJ}$, $615\mathrm{kJ}$ and $435\mathrm{kJ}$ respectively is $-$ ____ $\mathrm{kJ}$

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   Answer: 125

5. Q672024 · 4 Apr 2024 · Shift 2

   The correct order of the first ionization enthalpy is

   1. A.$\text{Ga}>\text{Al}>\text{B}$
   2. B.$\text{Tl}>\text{Ga}>\text{Al}$
   3. C.$\text{Al}>\text{Ga}>\text{Tl}$
   4. D.$\text{B}>\text{Al}>\text{Ga}$
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   Answer: B

6. Q662024 · 1 Feb 2024 · Shift 2

   The transition metal having highest $3^{\text{rd}}$ ionisation enthalpy is :

   1. A.$\mathrm{Mn}$
   2. B.$\mathrm{Fe}$
   3. C.$\mathrm{Cr}$
   4. D.$V$
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   Answer: A

7. Q802024 · 31 Jan 2024 · Shift 1

   The correct sequence of electron gain enthalpy of the elements listed below is A. Ar B. Br C. F D. S Choose the most appropriate from the options given below:

   1. A.$\mathrm{A}>\mathrm{D}>\mathrm{C}>\mathrm{B}$
   2. B.$\mathrm{A}>\mathrm{D}>\mathrm{B}>\mathrm{C}$
   3. C.$\mathrm{D}>\mathrm{C}>\mathrm{B}>\mathrm{A}$
   4. D.$\mathrm{C}>\mathrm{B}>\mathrm{D}>\mathrm{A}$
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   Answer: B

8. Q622024 · 29 Jan 2024 · Shift 1

   Given below are two statements : one is labelled as Assertion A and the other is labelled as Reason R : Assertion A : The first ionisation enthalpy decreases across a period. Reason R : The increasing nuclear charge outweighs the shielding across the period. In the light of the above statements, choose the most appropriate from the options given below :

   1. A.A is false but R is true
   2. B.Both A and R are true but R is NOT the correct explanation of A
   3. C.Both A and R are true and R is the correct explanation of A
   4. D.A is true but R is false
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   Answer: A

9. Q672024 · 29 Jan 2024 · Shift 2

   The element having the highest first ionization enthalpy is

   1. A.$\mathrm{C}$
   2. B.$\mathrm{Al}$
   3. C.$\mathrm{Si}$
   4. D.$\mathrm{N}$
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   Answer: D

10. Q822024 · 29 Jan 2024 · Shift 2· Numerical answer

    Standard enthalpy of vapourisation for $\mathrm{CC}{\mathrm{l}}_4$ is $30.5{\text{ kJ mol}}^{-1}$. Heat required for vapourisation of $284\text{ g}$ of $\mathrm{CC}{\mathrm{l}}_4$ at constant temperature is _________ kJ. (Given molar mass in ${\mathrm{gmol}}^{-1}$; $\mathrm{C}=12,\mathrm{Cl}=35.5$)

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    Answer: 56

11. Q902024 · 27 Jan 2024 · Shift 2· Numerical answer

    For a certain thermochemical reaction $\text{M}\to \text{N}$ at $\text{T}=400\text{ K}$, $\Delta {\text{H}}^{\ominus }=77.2{\text{ kJ mol}}^{-1}$, $\Delta \text{S}=122{\text{ JK}}^{-1}$, log equilibrium constant ($\log K$) is _______ $\times 10^{-1}$.

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    Answer: 37