On heating ammonium dichromate, the gas evolved is (a) Oxygen (b) Ammonia (c) Nitrous oxide (d) Nitrogen

A chemical reaction is a process where substances, known as reactants, transform into different substances, called products. In the case of ammonium dichromate, when it is heated, its molecules absorb energy and break down into simpler substances. This specific type of chemical reaction, where a single compound breaks down into two or more products, is known as a decomposition reaction. It's fascinating to observe how changes in conditions can induce such transformations; heating the compound supplies just the right amount of energy to initiate the reaction.
Decomposition reactions are not only essential in chemical studies but also play a crucial role in various industrial processes. For instance, the decomposition of limestone to lime and carbon dioxide is critical in cement production. Understanding these reactions can also be vital in environmental science, where the breakdown of compounds can affect ecosystems.

Balancing chemical equations is akin to solving a puzzle with the law of conservation of mass as your ultimate guide. This law states that mass can neither be created nor destroyed in a chemical reaction. Therefore, the mass of the reactants must be equal to the mass of the products. In our ammonium dichromate example, the balanced equation must have the same number of each type of atom before and after the reaction. To achieve this, you may need to adjust coefficients, which are numbers placed in front of compounds in an equation to ensure that the number of atoms for each element is conserved.
For instance, the balanced equation for the thermal decomposition of ammonium dichromate shows one molecule of the compound producing one molecule of chromium(III) oxide, one molecule of nitrogen gas, and four molecules of water. Striking the right balance is crucial for an accurate representation of the reaction, which is fundamental for predicting the outcome of a reaction and for calculating reactants and products accurately.

Thermal decomposition is a category of chemical reactions in which a compound breaks down into two or more substances when heated. This process is commonly endothermic, meaning it requires an input of energy in the form of heat. The ammonium dichromate example clearly illustrates thermal decomposition, as the compound decomposes into chromium(III) oxide, nitrogen gas, and water vapor when heated.
Thermal decomposition reactions are crucial in many fields. In materials science, understanding how materials decompose due to heat can lead to the development of heat-resistant materials. Also, in the field of thermodynamics, such reactions provide insight into the energy changes associated with chemical processes, deepening our understanding of energy conversion and storage. Recognizing these reactions helps in grasping concepts of energy flow and chemical changes, underpinning many industrial and scientific applications.