Question

What are three ways to increase the rate of the following reaction? $$ \mathrm{CaCO}_{3}(s)+2 \mathrm{HCl}(a q) \longrightarrow \mathrm{CaCl}_{2}(a q)+\mathrm{CO}_{2}(g)+\mathrm{H}_{2} \mathrm{O}(l) $$

Short answer

Three ways to increase the rate of the given reaction include: increasing the concentration of the reactants \(CaCO_{3}\) or \(HCl\), raising the temperature, and adding a catalyst.

Step-by-step solution

Increase Concentration of Reactants

Increasing the concentration of reactants makes more particles available for collisions, which can lead to more successful reactions. So, in this case, increasing the concentration of \(CaCO_{3}\) or \(HCl\) can increase the rate of the reaction.

Increase the Temperature

Increasing the temperature of the system increases the kinetic energy and motion of the reactant particles, making collisions more frequent and energetic. Therefore, raising the temperature would also increase the reaction rate.

Add a Catalyst

A catalyst is a substance that speeds up a reaction by providing an alternative reaction pathway with a lower activation energy. Therefore, adding a catalyst that is appropriate for this reaction would allow it to proceed faster without being consumed itself.

Key concepts

Reaction Kinetics

Understanding how to speed up chemical reactions requires a basic knowledge of reaction kinetics, which is the study of the rates of chemical processes. The rate of a reaction is influenced by several factors, which include the concentration of reactants, temperature of the system, presence of a catalyst, and surface area of solid reactants.

As seen in the textbook exercise, increasing the concentration of reactants is one practical way to increase reaction rate. Why does this work? It's because there are more reactant particles per unit volume that can collide and react. This concept is in line with the collision theory, which states that for a reaction to occur, reacting particles must collide with sufficient energy and a proper orientation. Higher concentration means more collisions, thus a greater chance for reactions.

Increase in temperature is another essential factor in reaction kinetics. When temperature rises, particles move faster due to increased kinetic energy. This leads to more frequent and energetic collisions, hence a higher reaction rate. This is why heating up reactants can be an effective method to speed up a reaction.

Chemical Equilibrium

While the exercise focuses on increasing reaction rates, it's important to be aware of chemical equilibrium, a state in a reversible chemical reaction where the rate of the forward reaction equals the rate of the reverse reaction, resulting in no net change in the concentration of reactants and products over time.

If we continually favor the production of reactants or products by altering conditions such as reactant concentration or temperature, we are essentially shifting the equilibrium position. For instance, Le Chatelier's principle tells us that increasing the concentration of reactants will push a reversible reaction to produce more products, until a new equilibrium is established. It's key to note that while these changes may increase the rate temporarily, in a closed system, a new equilibrium will be reached.

Catalysts in Chemistry

Catalysts are like the unsung heroes of the chemical world. They make reactions go faster without being consumed in the process, as highlighted in Step 3 of the solution. Catalysts in chemistry provide an alternative pathway with a lower activation energy compared to the uncatalyzed reaction. Activation energy is the minimum energy that reacting particles need to start a reaction.

For example, enzymes, which are biological catalysts, significantly speed up the reactions in living organisms. In industrial processes, catalysts are used to accelerate chemical reactions that would otherwise be too slow to be practical. However, it's crucial to choose the right catalyst for the right reaction. Just as a key fits a specific lock, a catalyst must be suitable for the specific reactants and conditions of the reaction it's meant to enhance. By lowering the activation energy, catalysts allow more reactant particles to have enough energy to react successfully, thereby increasing the reaction rate.