key term - Reactant

Definition

A reactant is a substance that participates in a chemical reaction, undergoing transformation to produce new substances known as products. Reactants are the starting materials that interact and rearrange their chemical bonds to form the final outcome of a reaction.

5 Must Know Facts For Your Next Test

1. Reactants are the initial substances present before a chemical reaction occurs, and they are consumed or transformed during the reaction.
2. The number and types of reactants involved in a reaction determine the stoichiometry, or the quantitative relationship between the reactants and products.
3. The rate of a reaction is influenced by the concentration of the reactants, as well as other factors such as temperature, pressure, and the presence of catalysts.
4. In a reversible reaction, the reactants and products are in a state of dynamic equilibrium, where the forward and reverse reactions occur at equal rates.
5. Le Châtelier's principle states that when a system at equilibrium is subjected to a change in concentration, temperature, or pressure, the system will shift to counteract the change and establish a new equilibrium state.

Review Questions

• Explain how the concentration of reactants affects the rate of a chemical reaction.
  • The concentration of reactants is a key factor in determining the rate of a chemical reaction. According to the collision theory, the rate of a reaction is proportional to the frequency of collisions between the reactant molecules. As the concentration of the reactants increases, the number of colliding molecules per unit of time also increases, resulting in a higher reaction rate. Conversely, if the concentration of reactants decreases, the collision frequency decreases, and the reaction rate slows down. This relationship between reactant concentration and reaction rate is an important principle in understanding and predicting the kinetics of chemical processes.
• Describe how Le Châtelier's principle can be used to predict the shift in equilibrium when the concentration of a reactant is changed.
  • According to Le Châtelier's principle, when a system at equilibrium is subjected to a change in concentration, the system will shift to counteract the change and establish a new equilibrium state. If the concentration of a reactant is increased, the system will shift to consume the additional reactant and produce more products, in order to reestablish the equilibrium. Conversely, if the concentration of a reactant is decreased, the system will shift to replenish the depleted reactant, producing more of it from the existing products. This predictable response of the equilibrium system to changes in reactant concentration is a powerful tool in understanding and manipulating chemical equilibria.
• Evaluate how the role of reactants in a chemical reaction is affected by the concept of chemical equilibrium and Le Châtelier's principle.
  • The role of reactants in a chemical reaction is fundamentally shaped by the concept of chemical equilibrium and Le Châtelier's principle. At equilibrium, the forward and reverse reactions occur at equal rates, and the concentrations of reactants and products remain constant. However, if the concentration of a reactant is changed, Le Châtelier's principle dictates that the system will shift to counteract this change and reach a new equilibrium state. This shift in equilibrium will involve the consumption or production of reactants, depending on the direction of the change. Understanding the interplay between reactants, equilibrium, and Le Châtelier's principle is crucial in predicting and manipulating the outcomes of chemical reactions, as well as in optimizing the conditions for desired products or processes.

Related terms

Product:

A product is the new substance formed as a result of a chemical reaction, created from the transformation of the reactants.

Chemical Equilibrium:

A state where the rate of the forward reaction and the rate of the reverse reaction are equal, resulting in no net change in the concentrations of the reactants and products.

Le Châtelier's Principle:

A principle that describes how a chemical system at equilibrium responds to changes in concentration, temperature, or pressure to counteract the change and reach a new equilibrium state.