Rate of reaction refers to

• A. The rate of reaction is the speed at which heat is released from the reaction.
• B. The rate of reaction is the speed at which products are formed or reactants are consumed.
• C. The rate of reaction is the energy change during the reaction.
• D. The rate of reaction is the equilibrium constant of the reaction.

Answer: (B)

Rate of reaction is the speed at which the reaction occurs, i.e., how quickly reactants are used up or products are formed. It is described by the change in concentration per unit time, typically measured as mol L⁻¹ s⁻¹. You can determine it by watching a reactant vanish or a product appear, and it can be an average over a time interval or an instantaneous value at a specific moment. This concept is about how fast the process happens, not about how much energy is released, the total energy change (enthalpy), or the position of equilibrium. Heat released relates to thermochemistry, while the energy change and the equilibrium constant describe different properties of a reaction.