Write the balanced chemical equation for the combustion of benzene, \(\mathrm{C}_{6} \mathrm{H}_{6}(\mathrm{l})\), to give carbon dioxide and water vapor. Would you expect \(\Delta S\) to be positive or negative in this process?

Combustion is a chemical process where a substance reacts with oxygen to produce heat and light. When we consider the combustion of benzene, classified as a hydrocarbon because it consists of carbon and hydrogen.The process of combustion transforms benzene into more stable compounds, namely carbon dioxide and water vapor. To ensure a complete reaction, sufficient oxygen must be present. This requirement leads us to the concept of balancing chemical equations, which is essential for understanding the quantitative aspects of chemical reactions.

Stoichiometry involves the calculation of reactants and products in chemical reactions. It's a vital concept for students to master because it provides insight into the conservation of mass during a reaction. Stoichiometry requires that every atom that enters a reaction must be accounted for in the products. When balancing the equation for combustion of benzene, the coefficients indicate the relative amounts of reactants and products. Successful balancing adheres to the Law of Conservation of Mass, ensuring that no atoms are lost or gained during the reaction. In the case of benzene's combustion, the final balanced equation indicates the precise proportion of benzene, oxygen, carbon dioxide, and water involved. Furthermore, considering stoichiometry aids in understanding the utilisation of reactants and the formation of products, which is crucial in industrial chemical reactions.

Entropy is a measure of disorder or randomness in a system, represented by the symbol A fundamental principle of entropy is that it tends to increase in spontaneous processes. In the context of chemical reactions, the state of the reactants and products plays a crucial role in entropy changes. During the combustion of benzene, the reactants are a liquid (benzene) and a gas (oxygen), while the products are gases (carbon dioxide and water vapor). Since gases have more randomness compared to liquids, increasing the number of gas molecules indicates an increase in entropy. Therefore, when we predict the change in entropy ( ) for the combustion of benzene, it is logical to expect a positive , signifying an increase in disorder as the reaction proceeds. This aligns with the Second Law of Thermodynamics, which states that for any spontaneous process, the total entropy of the system and its surroundings must increase.