Introduction

Enthalpy of neutralisation is a fundamental concept in acid-base reactions that measures the energy changes during the formation of water molecules. This topic is crucial for HSC Chemistry students studying the Properties of Acids and Bases module.

Definition and Basic Principles

The enthalpy of neutralisation (∆H) represents the energy released when one mole of water forms during an acid-base reaction. These reactions are exothermic, meaning they release energy to the surroundings, resulting in an increase in the solution's temperature.

Energy Calculations in Neutralisation Reactions

To calculate the energy transferred during neutralisation, we use the following equation:

$$q = mc\Delta T$$

Where:

Understanding Specific Heat Capacity

Specific heat capacity measures the energy needed to raise a substance's temperature by one Kelvin per unit mass. For water, this value is:

$$c_{water} = 4.18 \times 10^3 \text{ J kg}^{-1} \text{ K}^{-1}$$

This means that 4,180 Joules of energy are required to increase the temperature of one kilogram of water by one Kelvin.

Calculating Molar Enthalpy Change

The enthalpy change of neutralisation is calculated using:

$$\Delta H = -\frac{q}{n}$$

Where:

The negative sign indicates that energy is released during the reaction.

Experimental Considerations

It's important to note that experimental values often differ from theoretical values due to heat loss to the surroundings and other environmental factors. This leads to slightly less accurate measurements in practical settings.