Which of the following pair has heat of neutralization equal to -57.1kJ? (A) HNO3, KOH. (B)HCl, NH4OH. (C) H2SO4, NH4OH. (D) CH3COOH, NaOH?

Question

Answer

Answer

Answer is A.   Enthalpy of neutralization of any strong base with a strong acid or vice versa is always 57.1 kJ because they are completely ionized in dilute aqueous solution. If either acid or base or both are weak then the enthalpy of ionization less than 57.1 as they are not completely ionized. For completely dissociation of the weak base or weak acid a part of heat produced during combination of H+ and OH- ions is used up . so it is less than 57.1

Answer

Answer:

To determine which pair has a heat of neutralization equal to -57.1 kJ, we need to calculate the heat of neutralization for each pair and compare the results.

Heat of Neutralization:
The heat of neutralization is the enthalpy change that occurs when one mole of an acid reacts with one mole of a base to form one mole of water under standard conditions.

The general equation for the heat of neutralization is:
H+ (aq) + OH- (aq) → H2O (l)

Calculating the Heat of Neutralization:
To calculate the heat of neutralization, we can use the equation:

q = m × c × ΔT

Where:
q = heat transferred in joules (J)
m = mass of the solution in grams (g)
c = specific heat capacity of the solution in J/g·°C
ΔT = change in temperature in °C

Since we are dealing with a neutralization reaction, the change in temperature is usually small, so we can assume it to be negligible.

Analysis of the Options:

(A) HNO3, KOH:
The reaction between HNO3 (nitric acid) and KOH (potassium hydroxide) produces water and the salt potassium nitrate (KNO3). The heat of neutralization for this reaction is expected to be different from -57.1 kJ.

(B) HCl, NH4OH:
The reaction between HCl (hydrochloric acid) and NH4OH (ammonium hydroxide) produces water and the salt ammonium chloride (NH4Cl). The heat of neutralization for this reaction is expected to be different from -57.1 kJ.

(C) H2SO4, NH4OH:
The reaction between H2SO4 (sulfuric acid) and NH4OH (ammonium hydroxide) produces water and the salt ammonium sulfate (NH4)2SO4. The heat of neutralization for this reaction is expected to be different from -57.1 kJ.

(D) CH3COOH, NaOH:
The reaction between CH3COOH (acetic acid) and NaOH (sodium hydroxide) produces water and the salt sodium acetate (CH3COONa). The heat of neutralization for this reaction is expected to be different from -57.1 kJ.

Conclusion:
None of the given pairs have a heat of neutralization equal to -57.1 kJ. Therefore, the correct answer is None of the above.

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