Question

The equation which expresses the effect of temperature on the velocity constant of reaction is (a) Faraday (b) Arrhenius equation (c) Avogadro's equation (d) none of these

Short answer

The correct answer is (b) Arrhenius equation.

Step-by-step solution

Identify the relevant theory

Among the given options, identify which theory or principle refers to the effect that temperature has on the speed of chemical reactions.

Review Options

Review each of the listed equations. Faraday's laws are about electrolysis, Avogadro's law pertains to the number of particles in a given amount of gas and as such, neither is directly related to the effect of temperature on reaction velocity.

Decide on the correct answer

Upon reviewing the options, it can be remembered that the Arrhenius equation describes the impact of temperature on reaction rates, stating that as temperature increases, so does the speed of chemical reactions.

Key concepts

Temperature Effect on Reaction Rate

Understanding the influence of temperature on the rate of chemical reactions is critical for mastering the basics of chemical kinetics. In simple terms, as the temperature increases, the reaction rate usually increases too. This phenomenon can be explained by considering that temperature is a measure of kinetic energy within molecules. Higher temperatures mean that molecules move faster and collide more frequently and energetically, which in turn increases the likelihood of successful collisions that lead to chemical reactions.

From an Arrhenius perspective, each reaction has an activation energy barrier that molecules must overcome to react. Heating the mixture adds energy, allowing more molecules to attain the necessary energy to surmount the activation barrier, thereby accelerating the reaction. This relationship between temperature and reaction rate is one of the cornerstones of chemical kinetics, and it is quantitatively described by the Arrhenius equation, which predicts the rate of a reaction at different temperatures.

Chemical Kinetics

Chemical kinetics is the area of chemistry that deals with the rate of chemical reactions. It's not just about measuring how fast reactions occur, but also understanding the steps involved in a reaction mechanism and how different conditions, such as temperature, pressure, and concentration, affect this rate.

The Arrhenius equation is a key formula in this field as it links the rate constant of a reaction, denoted as \( k \), to the temperature and activation energy, symbolized as \( E_a \). The equation is given by \( k = A e^{-\frac{E_a}{RT}} \), where \( A \) is the pre-exponential factor, \( e \) is the base of the natural logarithm, \( R \) is the universal gas constant, and \( T \) is the temperature in Kelvin. This equation tells us that the reaction rate increases with an increase in temperature and decrease in activation energy. Understanding this relationship is vital for controlling reactions in industrial processes and in the laboratory.

Reaction Velocity

The term 'reaction velocity' or 'reaction rate' refers to the speed at which reactants are converted into products in a chemical reaction. It can be measured in various ways, such as the change in concentration of a reactant or product per unit time. For instance, if the concentration of a reactant decreases by 1 mol/L in 1 minute, the rate would be \( -1 \) mol/L/min. The negative sign indicates a decrease in concentration.

In chemical kinetics, determining reaction velocity is essential for understanding how quickly a reaction proceeds under certain conditions. The Arrhenius equation directly connects to this concept by providing a quantitative tool for predicting how factors like temperature affect the rate constant and therefore the reaction velocity. It enables chemists to calculate and compare the velocities of reactions at different temperatures, leading to better control and optimization in a range of applications, from industrial synthesis to environmental processes.