The equation for the formation of silicon tetrachloride from silicon and chlorine is Si(s) + 2Cl₂(g) → SiCl₄(g) + 657 kJ
b. Is the energy of the product higher or lower than the energy of the reactants?

Verified step by step guidance

1. Step 1: Begin by analyzing the chemical equation provided: Si(s) + 2Cl₂(g) → SiCl₄(g) + 657 kJ. The '+ 657 kJ' indicates that energy is released during the reaction, which classifies this as an exothermic reaction.
2. Step 2: Recall the concept of energy changes in chemical reactions. In an exothermic reaction, the energy of the products is lower than the energy of the reactants because energy is released to the surroundings.
3. Step 3: Understand that the energy released (657 kJ) represents the difference between the energy of the reactants and the energy of the products. This means the reactants had higher energy initially, and the products have lower energy after the reaction.
4. Step 4: Conclude that the energy of the product, SiCl₄(g), is lower than the energy of the reactants, Si(s) and Cl₂(g), due to the release of 657 kJ of energy.
5. Step 5: To reinforce understanding, consider the energy diagram for an exothermic reaction: the reactants start at a higher energy level, and the products end at a lower energy level, with the difference in energy released as heat.

Key Concepts

Exothermic Reactions

An exothermic reaction is a chemical reaction that releases energy in the form of heat or light. In the given equation, the formation of silicon tetrachloride from silicon and chlorine releases 657 kJ, indicating that the products have lower energy than the reactants. This energy release is a key characteristic of exothermic processes.

Enthalpy Change

Enthalpy change (ΔH) refers to the heat content of a system at constant pressure. In the context of the reaction provided, the negative value of ΔH (−657 kJ) signifies that the products (SiCl4) have a lower enthalpy than the reactants (Si and Cl2). Understanding enthalpy changes helps in predicting the energy dynamics of chemical reactions.

Thermodynamics

Thermodynamics is the branch of physical science that deals with the relationships between heat, work, temperature, and energy. It provides the framework for understanding how energy is transferred in chemical reactions. In this case, thermodynamic principles explain why the energy of the products is lower than that of the reactants, as energy is released during the formation of SiCl4.