Which of the following statements is true regarding spontaneous reactions?

• A. A spontaneous reaction is always a fast reaction.
• B. A spontaneous reaction always requires an external energy source.
• C. A spontaneous reaction is always a slow reaction.
• D. The spontaneity of a reaction is not necessarily related to the speed of a reaction.

Answer: (D)

Verified step by step guidance

1. Understand the concept of spontaneity: A spontaneous reaction is one that occurs without needing to be driven by an external energy source. It is determined by the change in Gibbs free energy (ΔG). If ΔG is negative, the reaction is spontaneous.
2. Differentiate between spontaneity and reaction rate: Spontaneity refers to the thermodynamic favorability of a reaction, while reaction rate refers to how fast a reaction proceeds. These are independent concepts.
3. Consider the factors affecting reaction rate: Reaction rate is influenced by factors such as temperature, concentration, surface area, and the presence of a catalyst, not by the spontaneity of the reaction.
4. Evaluate the given statements: A spontaneous reaction is not always fast or slow; its speed depends on kinetic factors, not on its thermodynamic spontaneity.
5. Conclude with the correct understanding: The correct statement is that the spontaneity of a reaction is not necessarily related to the speed of a reaction, as they are governed by different principles.