Question

Which is a decomposition reaction and which is not? a) \(\mathrm{Na}_{2} \mathrm{O}+\mathrm{CO}_{2} \rightarrow \mathrm{Na}_{2} \mathrm{CO}_{3}\) b) \(\mathrm{H}_{2} \mathrm{SO}_{3} \rightarrow \mathrm{H}_{2} \mathrm{O}+\mathrm{SO}_{2}\)

Short answer

Reaction (b) is a decomposition reaction; reaction (a) is not.

Step-by-step solution

Understand Decomposition Reaction

A decomposition reaction involves a single compound breaking down into two or more simpler substances. The general formula is \(AB \rightarrow A + B\).

Analyze Reaction (a)

Reaction (a) is: \(\mathrm{Na}_{2} \mathrm{O} + \mathrm{CO}_{2} \rightarrow \mathrm{Na}_{2} \mathrm{CO}_{3}\). Here, two compounds react to form one compound. This is not a decomposition reaction, rather it is a synthesis reaction.

Analyze Reaction (b)

Reaction (b) is: \(\mathrm{H}_{2} \mathrm{SO}_{3} \rightarrow \mathrm{H}_{2} \mathrm{O} + \mathrm{SO}_{2}\). Here, one compound, \(\mathrm{H}_{2} \mathrm{SO}_{3}\), breaks down into two simpler compounds, \(\mathrm{H}_{2} \mathrm{O}\) and \(\mathrm{SO}_{2}\). This fits the pattern of a decomposition reaction.

Key concepts

Chemical Reactions

Chemical reactions are events where substances, known as reactants, transform into different substances called products. These events involve breaking and forming bonds between atoms which result in new substances with distinct properties.
Understanding chemical reactions is crucial in chemistry because they explain how different materials interact and change.
Chemical reactions are broadly categorized into types such as synthesis, decomposition, displacement, and combustion reactions. Here are some basic characteristics:

• Reactants: Initial substances present before the process.
• Products: New substances formed as a result.
• Energy Change: Chemical reactions may release or absorb energy.
• Conservation of Mass: The mass of products equals the mass of reactants.

Chemical reactions are usually represented by chemical equations, which show the reactants and products involved in the processes. Understanding chemical reactions enables us to analyze reaction patterns, predict products, and recognize the type of process involved.

Synthesis Reaction

A synthesis reaction, also known as a combination reaction, occurs when two or more reactants combine to form a larger, more complex compound. Unlike a decomposition reaction that breaks down compounds, synthesis reactions build them from smaller units.
For example, reaction (a) from the exercise, ewline \(\mathrm{Na}_{2} \mathrm{O} + \mathrm{CO}_{2} \rightarrow \mathrm{Na}_{2} \mathrm{CO}_{3}\), woods showcases a synthesis reaction because two simple substances, sodium oxide and carbon dioxide, come together to form a more complex compound, sodium carbonate.
A general formula for a synthesis reaction is: \[A + B \rightarrow AB\] where \( A\) and \( B\) are reactants and \( AB\) is the product.
Such reactions are important in numerous fields, including industrial chemistry, where they are used to create complex materials from simpler raw materials.

Reaction Analysis

Analyzing chemical reactions is crucial for understanding how substances interact and transform. It involves examining the reactants and products, identifying reaction types, and understanding the process that occurs during the reaction.
For effective reaction analysis:

• Identify the reactants and predict their interactions.
• Evaluate the reaction type, for example, synthesis or decomposition.
• Balance chemical equations to ensure mass conservation.

Analyzing reaction (b) from the exercise, ewline \(\mathrm{H}_{2} \mathrm{SO}_{3} \rightarrow \mathrm{H}_{2} \mathrm{O} + \mathrm{SO}_{2}\), reveals it as a decomposition reaction, where a single compound \(\mathrm{H}_{2} \mathrm{SO}_{3}\) splits into two simpler substances \(\mathrm{H}_{2} \mathrm{O}\) and \(\mathrm{SO}_{2}\).
Understanding reaction analysis allows chemists to devise new methods to form desired products and to solve complex chemical questions.