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Thermodynamics question

2023 · 10 Apr · Shift 2 · Q18
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Thermodynamics question

2023 · 10 Apr · Shift 2 · Q18

JEE MainChemistryThermodynamicsNumerical+4 / −1
The number of endothermic process/es from the following is ‾\underline{\hspace{2cm}}​. A. I2( g)→2I(g)\mathrm{I}_{2}(\mathrm{~g}) \rightarrow 2 \mathrm{I}(\mathrm{g})I2​( g)→2I(g) B. HCl(g)→H(g)+Cl(g)\mathrm{HCl}(\mathrm{g}) \rightarrow \mathrm{H}(\mathrm{g})+\mathrm{Cl}(\mathrm{g})HCl(g)→H(g)+Cl(g) C. H2O(l)→H2O(g)\mathrm{H}_{2} \mathrm{O}(\mathrm{l}) \rightarrow \mathrm{H}_{2} \mathrm{O}(\mathrm{g})H2​O(l)→H2​O(g) D. C(s)+O2( g)→CO2( g)\mathrm{C}(\mathrm{s})+\mathrm{O}_{2}(\mathrm{~g}) \rightarrow \mathrm{CO}_{2}(\mathrm{~g})C(s)+O2​( g)→CO2​( g) E. Dissolution of ammonium chloride in water
Numerical answer
View written solutionFree

Correct answer: 4

  1. We need to count how many of the given processes are endothermic, i.e. processes for which heat is absorbed and hence ΔH>0\Delta H > 0ΔH>0.

  2. Analyze each process:

    A. I2(g)→2I(g)\mathrm{I_2(g) \rightarrow 2I(g)}I2​(g)→2I(g)

    • This is bond dissociation of iodine molecule.
    • Breaking a chemical bond requires energy.
    • Therefore, this process is endothermic.

    B. HCl(g)→H(g)+Cl(g)\mathrm{HCl(g) \rightarrow H(g) + Cl(g)}HCl(g)→H(g)+Cl(g)

    • This is also bond dissociation.
    • Breaking the H–Cl bond requires energy.
    • Therefore, this process is endothermic.

    C. H2O(l)→H2O(g)\mathrm{H_2O(l) \rightarrow H_2O(g)}H2​O(l)→H2​O(g)

    • This is vaporization of water.
    • Vaporization requires heat to overcome intermolecular forces.
    • Therefore, this process is endothermic.

    D. C(s)+O2(g)→CO2(g)\mathrm{C(s) + O_2(g) \rightarrow CO_2(g)}C(s)+O2​(g)→CO2​(g)

    • This is combustion/formation of carbon dioxide.
    • Combustion reactions release heat.
    • Therefore, this process is exothermic, not endothermic.

    E. Dissolution of ammonium chloride in water

    • Dissolving NH4Cl\mathrm{NH_4Cl}NH4​Cl in water causes cooling.
    • Hence heat is absorbed from surroundings.
    • Therefore, this process is endothermic.

  3. Count the endothermic processes:

    • A: Endothermic
    • B: Endothermic
    • C: Endothermic
    • D: Exothermic
    • E: Endothermic

    Total number of endothermic processes =4= 4=4.

  4. Final answer:

4\boxed{4}4​

  1. Comparison with stored correct answer:

Stored correct answer = 444.

My derived answer also = 444. So they agree.

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