JEE Main · 2024 · Shift-ImediumTHERMO-083

Given below are two statements: One is labelled as Assertion (A) and the other is labelled as Reason (R). Assertion…

Thermodynamics · Class 11 · JEE Main Previous Year Question

Question

Given below are two statements: One is labelled as Assertion (A) and the other is labelled as Reason (R).

Assertion (A): Enthalpy of neutralisation of strong monobasic acid with strong monoacidic base is always 57kJ mol1-57\,\text{kJ mol}^{-1}. Reason (R): Enthalpy of neutralisation is the amount of heat liberated when one mole of H+\text{H}^+ ions furnished by acid combine with one mole of OH\text{OH}^- ions furnished by base to form one mole of water.

In the light of the above statements, choose the correct answer from the options given below:

Options
  1. a

    A true, R false

  2. b

    Both true, R not correct explanation

  3. c

    Both true, R is correct explanation

  4. d

    A false, R true

Correct Answerc

Both true, R is correct explanation

Detailed Solution

🧠 Standard enthalpy of neutralization of strong acid with strong base = 57-57 kJ/mol because the net reaction is always \ceH++OH>H2O\ce{H+ + OH- -> H2O} Both strong acid and strong base are fully dissociated in solution. No ionisation energy is needed. The only process is: \ceH+(aq)+OH(aq)>H2O(l),ΔH=57 kJ mol1\ce{H+(aq) + OH-(aq) -> H2O(l)}, \quad \Delta H = -57\text{ kJ mol}^{-1}

Assertion A is true — it's always 57-57 kJ/mol for strong acid + strong base. Reason R is also true and correctly explains why: 1 mol of \ceH+\ce{H+} from the acid combines with 1 mol of \ceOH\ce{OH-} from the base. R is the correct explanation.

Answer: (c)\boxed{\text{Answer: (c)}}

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