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10: Enthalpy of Neutralization

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    514172

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    PURPOSE
    • To use coffee-cup calorimetry to determine the enthalpy of neutralization of two acids, hydrochloric acid and acetic acid, with sodium hydroxide.

    INTRODUCTION

    The enthalpy of neutralization (ΔHneut) is the heat released or absorbed when an aqueous acid and base react to form one mole of water. In this experiment, the enthalpy of neutralization for two distinct acid–base reactions will be measured using a coffee-cup calorimeter, a constant-pressure device designed to insulate aqueous chemical reactions from ambient thermal loss.

    The first system involves a strong acid (HCl) and a strong base (NaOH), both of which ionize completely in aqueous solution. The second system involves a weak acid (CH3CO2H) and a strong base (NaOH). Because weak acids exist primarily as unionized molecules in solution, a portion of the neutralization energy is consumed in breaking the covalent O–H bond to release protons. By measuring precise temperature changes during these reactions, the net heat released (qrxn) can be calculated and normalized per mole of water produced.

    Additionally, the heat capacity of the calorimeter apparatus (Ccalorimeter) will be determined by mixing warm and cold water. Accounting for thermal energy absorbed by the polystyrene container and temperature probe ensures greater quantitative accuracy when evaluating the fundamental differences between strong and weak acid thermodynamics.

    • 10.1: Enthalpy of Neutralization - Experiment
      This page details laboratory safety measures and required equipment for experiments with sodium hydroxide, hydrochloric acid, and acetic acid. It stresses caution with corrosive substances, the importance of personal protective gear, and working in ventilated spaces. The experimental procedure includes measuring the heat capacity of a calorimeter and calculating the enthalpy of neutralization for NaOH with both acids. Guidelines for proper disposal of chemical waste are also included.
    • 10.2: Enthalpy of Neutralization - Pre-lab
      This page covers pre-lab questions related to thermodynamics and calorimetry, emphasizing the First Law of Thermodynamics and coffee-cup calorimetry. Students are tasked with writing a balanced equation for the NaOH and HCl reaction, determining the limiting reactant, and calculating the enthalpy of neutralization. It also requires finding the net ionic equation and the theoretical standard enthalpy of neutralization using thermochemical data.
    • 10.3: Enthalpy of Neutralization - Data and Report
      This page details the experimental procedures for measuring heat capacity and enthalpy of neutralization, divided into three parts: Part A calculates the heat capacity of a calorimeter through temperature changes, Part B assesses the enthalpy of neutralization for HCl and NaOH, and Part C does the same for CH3CO2H and NaOH. Each section features tables for data recording and includes post-lab questions that analyze thermal data and compare enthalpies.

    This page titled 10: Enthalpy of Neutralization was last modified on Thu, 01 Oct 2026 18:24:52 GMT and is shared under a CC BY 4.0 license and was authored, remixed, and/or curated by Vincent Hradil and Saadia Khan.