Chapter 18, Problem 56A

Interpretation Introduction

Interpretation: The true statement is to be explained from the given statements.

Concept Introduction: The rate at which reactants are transformed into products is referred to as the rate of reaction or simply the reaction rate.

Answer to Problem 56A

Increasing the surface area of a reactant increases the collision frequency and reaction rate. Since more surface area is available for collisions, the faster the reaction occurs.

Explanation of Solution

The given statements are as follows:

1. An increase in temperature tends to slow down the rate of chemical reactions.
2. Once a chemical reaction has started, it is no longer necessary for the reacting particles to collide for products to form.
3. Increasing the overall surface area of solid or liquid reactants accelerates the reaction rate.

Reason for true statement:

c. Increasing the surface area of a reactant both increases the frequency of collisions and accelerates the pace at which the reaction occurs. This is because the more available surface area there is for particles to collide, the faster the reaction will take place.

Reason for false statements:

1. Generally, increasing the temperature will accelerate chemical reactions. The molecules will collide more frequently as the temperature increases because they will move faster. Therefore, the reaction will be more likely to occur as collisions increase.
2. Even after a chemical reaction has started, the reacting particles still need to collide to produce the reaction's products.

Conclusion

Increasing the surface area of a reactant increases the collision frequency and reaction rate. Since more surface area is available for collisions, the faster the reaction occurs.