A Level Chemistry OCR Practice Exam

What occurs during thermal decomposition reactions?

1. Only one product is formed

2. Substances can break down into multiple products with heat

3. New chemical bonds are formed without the addition of heat

4. Molecules are rearranged into isomers

The correct answer is: Substances can break down into multiple products with heat

During thermal decomposition reactions, substances are subjected to heat, causing them to break down into simpler products. This process can yield multiple products depending on the compound being decomposed and the conditions of the reaction. The heat provides the necessary energy to overcome the bonds present in the original compound, leading to the formation of various smaller molecules or elements. This option accurately reflects the nature of thermal decomposition, which contrasts with the notion that only one product is formed, as many reactions can yield a mixture of products. Furthermore, while new chemical bonds are indeed formed during a reaction, the defining characteristic of thermal decomposition is the breakdown of the original substance, which typically does not occur without the application of heat. Lastly, while molecules can rearrange, the specific rearrangement into isomers does not capture the essence of thermal decomposition, which focuses on the breakdown into simpler entities rather than just structural rearrangements. Thus, the understanding that thermal decomposition reactions can produce multiple products highlights their complexity and the diversity of outcomes that can result from such processes.