[Single-digit Integer] Volumes of 50 ml of 1 M- and 50 ml of 1 M- both at the same temperature were mixed in a calorimeter of very small heat capacity. A temperature rise of 411 K was recorded. In a s

Question

[Single-digit Integer] Volumes of 50 ml of 1 M-$NaOH$ and 50 ml of 1 M-$HCl$ both at the same temperature were mixed in a calorimeter of very small heat capacity. A temperature rise of 411 K was recorded. In a second experiment, the $HCl$ was replaced by 50 ml of 1 M-HCOOH. The temperature rise was 321 K. The enthalpy of ionization of HCOOH is (in kcal/mol)

Prashant Kotian · Accepted Answer

Correct answer: 0003. Heat of neutralization of strong acid vs strong base is -13.7 kcal/eq. Temperature rise for strong acid neutralization is 411 K, releasing some heat Q1. For weak acid (HCOOH), temperature rise is 321 K, releasing heat Q2.
The difference in temperature rise represents the heat of ionization of HCOOH:
Enthalpy of ionization = ΔH_ionization = +3 kcal/mol.

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