Equal volumes of one molar hydrochloric acid and one molar sulphuric acid are neutralized completely by dilute \(\mathrm{NaOH}\) solution by which \(X\) and \(Y\) kcal of heat are liberated, respectively. Which of the following is true? (a) \(X=Y\) (b) \(2 X=Y\) (c) \(X=2 Y\) (d) none of these

When we talk about neutralization reactions, we refer to the chemical process where an acid and a base react to form water and a salt. This reaction is quintessential in understanding how different substances can combine to form completely new products. For instance, in our exercise, hydrochloric acid (HCl) reacts with sodium hydroxide (NaOH) to produce sodium chloride (NaCl) and water (H₂O). Similarly, sulphuric acid (H₂SO₄) reacts with NaOH to produce sodium sulphate (Na₂SO₄) and water. The unique characteristic of these reactions is the idea of equivalence - it takes exact amounts of acid and base to achieve a neutral solution, meaning the solution has a pH of 7. In the course of these neutralization processes, energy is released in the form of heat, which can be measured and is a topic of interest in calorimetry studies.

Understanding these reactions requires comprehension of the ratio in which the reactants combine, which is dictated by their respective chemical formulas. HCl combines with NaOH in a 1:1 ratio, whereas H₂SO₄ requires twice the amount of NaOH because it contains two replaceable hydrogen ions per molecule, resulting in a 1:2 ratio.

Enthalpy change, often expressed as \( \Delta H \), is a term used in chemistry to describe the amount of heat absorbed or released during a chemical reaction at constant pressure. When a reaction occurs, bonds are broken and formed, which involves energy. If the reaction releases heat, it is exothermic, and the enthalpy change is negative. On the contrary, if the reaction absorbs heat, it is endothermic, and the enthalpy change is positive.

In the context of neutralization reactions, these tend to be exothermic. For strong acid and base pairs, the enthalpy change is fairly constant, often releasing around 13.7 kcal/mol of reactants. This consistent release of energy is due to the formation of water from H⁺ ions and OH⁻ ions. Moreover, this provides us with a way to measure the strength of an acid or base: by calculating the heat liberated during the neutralization, we gain insight into their reactivity and behavior in solution.

Stoichiometry is the section of chemistry that pertains to the calculation of reactants and products in chemical reactions. It is the backbone of reactions, providing the quantitative relationship between the amounts of substances involved. Through stoichiometry, we determine the proportional ratios needed to react completely without any excess of either reactant.

In our exercise, stoichiometry plays a critical role in understanding why sulphuric acid (H₂SO₄) releases twice the heat compared to hydrochloric acid (HCl) when reacting with sodium hydroxide (NaOH). It all comes down to the stoichiometric coefficients: two moles of NaOH are required to completely neutralize one mole of H₂SO₄ due to the presence of two acidic protons in the sulphuric acid molecule. Therefore, the stoichiometry tells us that the number of heat units released in the reaction against sulphuric acid would be double that of hydrochloric acid.

Acid-base reactions, known as neutralizations, are fundamental chemical processes where hydrogen ions, H⁺ (protons), from the acid react with hydroxide ions, OH⁻, from the base to form water molecules. An acid is a substance that can donate a proton, while a base is a substance that can accept a proton.

These reactions can be represented by a general equation: acid + base → salt + water. What is interesting about these reactions is that a strong acid like hydrochloric acid (HCl) will react vigorously with a strong base like sodium hydroxide (NaOH), resulting in a significant heat release. This is why measuring the heat of neutralization is a practical way to examine the strength and behavior of acids and bases in chemical reactions. Remember, a 'strong' acid or base is one that completely dissociates in solution, so the concentration of H⁺ or OH⁻ ions in a solution of a strong acid or base is equal to the concentration of the acid or base itself.