Question

Explain why a crushed solid reacts with a gas more quickly than a large chunk of the same solid.

Short answer

A crushed solid reacts with a gas more quickly than a large chunk of the same solid because it has a larger surface area. The increased surface area provides more sites for gas molecules to collide and react with, leading to more frequent and effective collisions. Consequently, the reaction rate is higher for crushed solid compared to a large chunk of the substance, highlighting the importance of surface area in influencing reaction rates.

Step-by-step solution

Understand the concept of reaction rate

Reaction rate refers to how fast or slow a chemical reaction occurs. The rate of a chemical reaction can be influenced by various factors, such as temperature, concentration of reactants, and surface area of solid reactants. In this case, we will focus on the effect of surface area on the reaction rate between a crushed solid and a gas, compared to a large chunk of the same solid.

Recognize the importance of surface area

The surface area of a solid reactant plays a crucial role in determining the rate of reaction. When a solid (either a large chunk or crushed particles) comes into contact with a gas, chemical reactions occur at the surface of the solid. Thus, the greater the surface area of the solid, the more sites are available for the gas molecules to collide with and react, leading to a faster reaction rate.

Compare the surface area of crushed solid and large chunk

When we crush a solid into smaller particles, we significantly increase its overall surface area. This is because the smaller particles expose more of their internal surfaces, providing more opportunities for the gas molecules to collide and react. On the other hand, a large chunk of the solid has a smaller surface area, limiting the number of sites available for the gas molecules to react.

Relate surface area to reaction rate

As we have established that crushed solid has a larger surface area compared to a large chunk of the same substance, we can now relate this to the reaction rate. The crushed solid provides more surface area for the gas molecules to collide and react with, leading to more frequent and effective collisions. This, in turn, results in a faster reaction rate between the crushed solid and the gas.

Conclusion

A crushed solid reacts with a gas more quickly than a large chunk of the same solid due to its larger surface area. The larger surface area provides more sites for gas molecules to collide and react with, resulting in a higher reaction rate. This demonstrates the importance of surface area in influencing the rate of chemical reactions.

Key concepts

Surface Area in Chemistry

Understanding the role of surface area in chemistry is crucial when studying reaction kinetics. Surface area pertains to the amount of exposed area of a substance that is accessible for reaction with other substances. For solid reactants, this is particularly important because reactions occur at the interface between the solid and the other reactant, often a gas or liquid.

In the given exercise, we examine why a crushed solid reacts more rapidly with a gas than a large chunk. The essence lies in the fact that when solids are crushed into finer pieces or powders, the total surface area available for chemical reactions with the gas increases dramatically. Smaller particles mean more exposed surfaces, and consequently, higher chances for gas molecules to collide with the solid's surface. This is why powdered reactants are preferred in industries that require fast and efficient chemical processes.

Visualizing Surface Area

Think of it like a block of cheese versus grated cheese. If you melt them, the grated cheese will melt faster because heat can reach more parts of the cheese due to the increased surface area. Similarly, in chemistry, greater surface area facilitates more collisions, leading to faster chemical reactions.

Rate of Chemical Reaction

The rate of a chemical reaction is a measure of the speed at which reactants are converted into products. It's often expressed as the change in concentration of a reactant or product per unit of time. For instance, higher reaction rates imply that the reactants are being consumed or the products are being formed more quickly.

Projecting this onto the exercise example, we infer that the crushed solid's increased surface area accelerates the reaction rate with the gas. More surface area means more available sites at any given moment for the gas molecules to interact, facilitating a greater number of successful collisions. This results in the crushed solid reacting more quickly in comparison to the larger chunk.

Factors Influencing Reaction Rates

Apart from surface area, other factors include temperature, concentration of reactants, presence of catalysts, and the intrinsic nature of the reactants themselves. Each factor independently and interdependently affects how swiftly a chemical reaction proceeds.

Factors Affecting Reaction Rate

Various factors can affect the rate at which a chemical reaction proceeds. Let's highlight the key ones in relation to our exercise scenario:

• Temperature: Generally, increasing the temperature increases the kinetic energy of particles, leading to more collisions and a higher reaction rate.
• Concentration: Higher concentrations of reactants usually increase the frequency of collision between reacting particles, thus increasing the reaction rate.
• Presence of a Catalyst: Catalysts speed up reactions without being consumed by lowering the activation energy required for the reaction to proceed.
• Nature of Reactants: Some substances are simply more reactive due to their atomic or molecular structure. For example, metals tend to lose electrons and react quicker than nonmetals.

Surface area, as explored in our exercise, significantly affects reaction rates. It's especially relevant in heterogeneous reactions where reactants are in different phases. By increasing the surface area of the solid reactant through crushing or grinding, we amplify the reaction rate by providing more active sites for the reaction to take place. This principle is widely applied in industries such as pharmaceuticals and materials science to control and optimize reactions.