Chapter 17 Quiz - Chemistry

The symbol "Ea" is used to represent the term "activation energy" or "energy of activation". Activation energy refers to the minimum amount of energy required for a chemical reaction to occur. It is the energy barrier that needs to be overcome for the reactants to convert into products. The term "energy of activation" is also used interchangeably with activation energy and represents the same concept. Both terms are commonly used in chemistry to describe this crucial energy requirement in chemical reactions.

The explanation for the given correct answer is that the likelihood of a completed reaction depends on the energy of the initial collision. In order for a reaction to occur, the molecules must collide with enough energy to overcome the activation energy barrier. If the collision is energetic enough, it can provide the necessary activation energy for the reaction to proceed. Therefore, the statement that the likelihood of a completed reaction depends on the energy of the initial collision is true.

An increase in pressure can increase the reaction rate in gases because it leads to a higher concentration of gas molecules in a given volume. This increased concentration means that there are more frequent collisions between the reactant molecules, which increases the chances of successful collisions and therefore increases the reaction rate.

An increase in temperature can actually increase the reaction rate in many cases. This is because higher temperatures provide more kinetic energy to the reactant molecules, causing them to move faster and collide more frequently, leading to a higher likelihood of successful collisions and increased reaction rate. However, there may be some exceptions where an increase in temperature can decrease the reaction rate, such as when the reaction is endothermic and requires heat to proceed.

Chemical equilibrium refers to a state in a reaction where the forward and backward reactions occur at the same rate, resulting in no net change in the concentrations of reactants and products. When placed under new conditions such as changes in temperature, pressure, or concentration, the equilibrium position can shift. This means that the concentrations of reactants and products may change, and the equilibrium will be reestablished at a new point. Therefore, the statement that chemical equilibrium for a reaction is different when placed under new conditions is true.

This statement is false because not every collision results in a completed reaction. In some cases, collisions may not have enough energy or the correct orientation to result in a reaction. Additionally, certain factors such as the presence of catalysts or inhibitors can also influence whether a collision leads to a completed reaction or not. Therefore, it is incorrect to say that every collision results in a completed reaction.

Catalysts are substances that can speed up a chemical reaction without being consumed in the process. They work by lowering the activation energy required for the reaction to occur, allowing it to happen more quickly. Since catalysts are not used up in the reaction, they can be used repeatedly, making them highly efficient and cost-effective. Therefore, the statement that catalysts are useful for increasing reaction rates because they are not consumed in the reaction and may be reused is true.

Enzymes are biological catalysts that facilitate chemical reactions in living organisms. However, they are highly sensitive to temperature changes. When the temperature of the system is too high, enzymes can denature, meaning their structure and shape become altered, leading to a loss of functionality. This is because high temperatures disrupt the weak bonds that maintain the enzyme's specific shape, rendering it unable to bind to its substrate and catalyze reactions effectively. Therefore, it is true that enzymes lose functionality when the temperature of the system is too high.

Lowering the temperature decreases the reaction rate of a chemical reaction in a gaseous system because it reduces the kinetic energy of the particles in the system. When the temperature is lowered, the particles move slower and have less energy to overcome the activation energy barrier, resulting in a slower reaction rate.

In a reaction rate energy diagram, the reaction is considered exothermic when the potential energy of the products is lower than that of the reactants. This means that the reaction releases energy in the form of heat to the surroundings. In an exothermic reaction, the reactants have higher potential energy than the products, and the difference in energy is released as heat. This is opposite to an endothermic reaction, where the potential energy of the products is higher than that of the reactants, and energy is absorbed from the surroundings.

A catalyst works by lowering the activation energy of a reaction. Activation energy is the energy required to start a chemical reaction. By lowering this energy barrier, a catalyst allows the reaction to proceed more easily and quickly. It does not directly affect the amount of space between particles, the kinetic energy of the particles, or the collision rate. Instead, it provides an alternative reaction pathway with a lower activation energy, making the reaction more favorable.

Dynamic equilibrium of a system occurs when the rates of the forward and reverse reactions are equal, not when the products equal the reactants. In dynamic equilibrium, the concentrations of the reactants and products remain constant over time, but they do not necessarily have to be equal.

Static equilibrium within a system means that the forward reaction and the reverse reaction have reached a balance, where the rates of the two reactions are equal. In other words, the system is not undergoing any net change or progress. Therefore, the correct answer is false because static equilibrium implies that the forward and reverse reactions are occurring at the same rate.

The activation energy of a reaction refers to the energy required to break the existing bonds in the reactants. It is the minimum energy needed for the reaction to occur and for new bonds to form in the products.