Reactants

Definition

Reactants are the starting substances in a chemical reaction that undergo transformation to form products. They are crucial because they provide the necessary atoms and molecules that interact during the reaction, leading to new compounds. Understanding reactants is key to grasping how chemical bonds break and form, as well as how energy changes throughout the process.

5 Must Know Facts For Your Next Test

1. Reactants can be elements or compounds that are present before a reaction occurs and must be in the right proportions for the reaction to take place effectively.
2. The law of conservation of mass states that during a chemical reaction, mass is neither created nor destroyed, meaning that the total mass of reactants equals the total mass of products.
3. In many reactions, reactants need to overcome activation energy for a reaction to proceed, which can often be facilitated by catalysts.
4. Reactants may change state during a reaction, such as from solid to liquid or gas, which can impact how they interact with each other.
5. Identifying reactants is essential for predicting the outcome of a chemical reaction, including what products will form and whether the reaction is exothermic or endothermic.

Review Questions

• How do reactants relate to the concept of activation energy in a chemical reaction?
  • Reactants must possess enough energy to overcome activation energy for a chemical reaction to occur. This energy is needed for the bonds in reactants to break so that new bonds can form during the transformation into products. The amount of activation energy required can determine whether a reaction occurs spontaneously or needs an external input like heat or a catalyst.
• Explain how the law of conservation of mass applies to reactants and products in a chemical equation.
  • The law of conservation of mass states that matter cannot be created or destroyed in a chemical reaction. This principle means that the total mass of reactants before the reaction must equal the total mass of products after the reaction. In writing a balanced chemical equation, it’s essential to ensure that the number of atoms of each element is conserved, reflecting that all atoms present in the reactants are accounted for in the products.
• Analyze how changing concentrations of reactants can influence the rate of a chemical reaction and its equilibrium.
  • Changing the concentration of reactants can significantly affect the rate at which a chemical reaction proceeds. Increasing reactant concentrations typically leads to more frequent collisions between particles, thus increasing the rate of reaction. Furthermore, according to Le Chatelier's principle, altering reactant concentrations can shift the equilibrium position of reversible reactions, potentially favoring either reactant or product formation depending on whether concentrations are increased or decreased.

Related terms

Products: Products are the substances that result from a chemical reaction, formed when reactants undergo a transformation.

Chemical Equation: A chemical equation is a symbolic representation of a chemical reaction, showing the reactants on one side and the products on the other, usually separated by an arrow.

Activation Energy: Activation energy is the minimum energy required for reactants to collide successfully and initiate a chemical reaction.