Question

Which of the following is true concerning a reaction that begins with only reactants and moves to equilibrium? A. The rate of the forward and reverse reactions decreases until cquilibrium is reached. B. The rate of the forward and reverse reactions increases until equilibriam is reached. C. The rate of the forward reaction decreases, and the rate of the reverse reaction increases until equilibrium is reaclyed. D. The rate of the forward reaction increases, and the rare of the reverse reaction decreases until equilibrium is reached.

Short answer

C. The rate of the forward reaction decreases, and the rate of the reverse reaction increases until equilibrium is reached.

Step-by-step solution

Understand Chemical Equilibrium

Chemical equilibrium occurs when the rate of the forward reaction equals the rate of the reverse reaction. At this point, the concentrations of reactants and products remain constant.

Analyze Rate Changes

As a reaction progresses towards equilibrium, the rate of the forward reaction (starting with only reactants) will typically decrease because the concentration of reactants decreases.

Compare with Reverse Reaction

Simultaneously, the rate of the reverse reaction will increase as the concentration of products increases.

Determine the Correct Answer

The scenario described matches option C: 'The rate of the forward reaction decreases, and the rate of the reverse reaction increases until equilibrium is reached.'

Key concepts

reaction rates

In chemical reactions, reaction rates refer to how quickly or slowly reactants are converted to products. Reaction rates can change based on various conditions such as temperature, pressure, and the concentration of reactants. Here's what you need to know about reaction rates:

• Initial Rate: At the very start, when you have only reactants, the reaction rate is at its highest because the concentration of reactants is also high.
• Changes Over Time: As the reaction advances, the concentration of reactants decreases. This typically results in a decrease in the rate of the forward reaction.
• Influence of Products: Simultaneously, as products begin to form, the rate of the reverse reaction tends to increase, because the concentration of products is becoming significant.

Understanding these dynamics is crucial in predicting how a reaction will behave as it moves towards equilibrium.

equilibrium state

The equilibrium state is a key concept in chemical reactions. It represents a balanced situation where the rates of the forward and reverse reactions are equal. Here are some detailed points about the equilibrium state:

• Constant Concentrations: When equilibrium is reached, the concentrations of reactants and products do not change. This doesn't mean the reactions stop; they continue to occur, but at the same rate in both directions.
• Dynamic Balance: Equilibrium is dynamic, meaning that the molecules of reactants and products are continually reacting, but there's no net change in their overall concentrations.
• Predictability: By understanding the equilibrium state, chemists can predict how changes in conditions (like pressure or temperature) will affect the concentrations of reactants and products.

The equilibrium concept helps in various practical applications, from industrial synthesis processes to biological systems.

forward and reverse reactions

Every chemical reaction involves a forward and a reverse reaction. Here's a detailed look:

• Forward Reaction: This is the reaction that converts reactants to products. Initially, with a high concentration of reactants, the rate is fast. Over time, as reactants are used up, the rate decreases.
• Reverse Reaction: This reaction converts products back into reactants. Initially, it is slow due to the low concentration of products. As more products form, the rate of the reverse reaction increases.
• Reaching Equilibrium: A unique point is reached where the rates of the forward and reverse reactions are equal. At this point, the system is in equilibrium.

Understanding the dynamics between these two reactions is crucial for manipulating and controlling chemical processes in labs and industries.