In acid base chemistry, which of the following balanced equations correctly represents a neutralisation reaction between an acid and a base to form a salt and water?

Introduction / Context:
Neutralisation reactions are a key concept in acid base chemistry. They occur when an acid reacts with a base to produce a salt and water. Many exam questions ask students to identify which of several chemical equations represents a true neutralisation process. This question provides several balanced equations that look similar and requires the learner to select the one that clearly shows an acid and a base reacting to form a salt and water as products.

Given Data / Assumptions:
- Neutralisation is defined as the reaction of an acid with a base to form a salt and water.
- Each option shows a balanced chemical equation with different reactants and products.
- We assume standard aqueous acid base chemistry at the school level.
- The presence of an acid and a metal hydroxide or similar base must be evident for true neutralisation.

Concept / Approach:
To identify a neutralisation reaction, look for an acid (such as H2SO4) reacting with a base (such as NaOH) and forming a salt (Na2SO4) and water (H2O). Decomposition reactions, redox reactions and simple dissolving or dehydration reactions are not neutralisation. In the given options, only the reaction in option B shows an acid and a base reacting to form a salt and water. The other equations represent decomposition of hydroxides, combustion of hydrogen, breakdown of carbonic acid and dissociation of a salt rather than acid base neutralisation.

Step-by-Step Solution:
Step 1: Examine option A. It shows aluminium hydroxide breaking down into aluminium oxide and water. This is a thermal decomposition, not a reaction with an acid. Step 2: Examine option B. It shows sulfuric acid, H2SO4, reacting with sodium hydroxide, NaOH, to produce sodium sulfate, Na2SO4, and water. This fits the definition of neutralisation. Step 3: Examine option C. It is the combustion of hydrogen gas with oxygen to form water, which is a redox reaction rather than acid base neutralisation. Step 4: Examine option D. It shows carbonic acid decomposing into carbon dioxide and water, a decomposition reaction rather than reaction with a base. Step 5: Examine option E. It shows the dissociation of sodium chloride into ions in solution, which is just dissolving, not neutralisation. Therefore, option B is the correct neutralisation equation.

Verification / Alternative check:
In simple acid base theory, neutralisation can be represented using net ionic equations such as H+(aq) + OH-(aq) --> H2O(l). When expanded to full molecular equations, a typical example is HCl(aq) + NaOH(aq) --> NaCl(aq) + H2O(l). The pattern of an acid plus a base yielding a salt and water matches exactly what is seen in option B, where H2SO4 provides H+ ions and NaOH provides OH- ions. The resulting salt Na2SO4 and water fit the expected neutralisation products. None of the other equations has this acid plus base pattern, which confirms the choice.

Why Other Options Are Wrong:
Option A is a decomposition of aluminium hydroxide under heat and does not involve an acid. Option C is a combustion reaction where hydrogen burns in oxygen to form water, not a reaction between an acid and a base. Option D shows the breakdown of carbonic acid into carbon dioxide and water, which is a decomposition often related to escape of gas from solution, not neutralisation. Option E describes ionic dissociation when salt dissolves in water, not a reaction where an acid is neutralised by a base. These processes are important in chemistry but are not examples of neutralisation in the acid base sense.

Common Pitfalls:
Learners may be distracted by the presence of water in the products and assume that any equation producing water must represent neutralisation. This leads to confusion with combustion and decomposition reactions. Another pitfall is to focus only on the change in states, such as solid to aqueous, instead of identifying acids and bases. To avoid mistakes, students should always check whether an acid and a base are reacting and whether a salt and water are formed as products. Following this guideline makes it clear that option B is the only true neutralisation reaction in the list.

Final Answer:
The equation that represents a neutralisation reaction is H2SO4(aq) + 2NaOH(aq) --> Na2SO4(aq) + 2H2O(l).