The given graph is a representation of kinetics of a reaction.
The y and x axes for zero and first order reactions, respectively are
The y and x axes for zero and first order reactions, respectively are
- zero order (y = concentration and x = time), first order (\(y = t\frac{1}{2}\), and x = concentration)
- zero order (y = concentration and x = time), first order (y = rate constant and x = concentration)
- zero order (y = rate and x = concentration), first order (\(y = t\frac{1}{2}\) and x = concentration)
- zero order (y = rate and x = concentration), first order (y = rate and \(x = t\frac{1}{2}\))
The Correct Option is C
Solution and Explanation
To determine the correct representation of the given kinetic graph for zero and first-order reactions, let's examine each order:
Zero-order reaction: In a zero-order reaction, the rate of the reaction is constant and independent of the concentration of the reactants. The equation is:rate = k, where k is the rate constant. When graphed, plotting the rate against the concentration results in a horizontal line, indicating that the rate does not change with concentration.
First-order reaction: In a first-order reaction, the rate is directly proportional to the concentration of one reactant. The equation can be written as: rate = k[A], where [A] is the concentration of the reactant. Additionally, the half-life (t1/2) of a first-order reaction is independent of the concentration and is given by t1/2 = 0.693/k. Graphically, when plotting t1/2 against the concentration, there should be no dependency, suggesting a constant horizontal line.
Given these descriptions, the correct graph representations for zero and first-order reactions match the described solution:
| Reaction Order | y-axis | x-axis |
|---|---|---|
| Zero-order | Rate | Concentration |
| First-order | \(t_{1/2}\) | Concentration |
The correct answer corresponds to: Zero-order (y = rate and x = concentration), first-order (y = t1/2 and x = concentration).
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Concepts Used:
Chemical Kinetics
Chemical kinetics is the description of the rate of a chemical reaction. This is the rate at which the reactants are transformed into products. This may take place by abiotic or by biological systems, such as microbial metabolism.
Rate of a Chemical Reaction:
The speed of a reaction or the rate of a reaction can be defined as the change in concentration of a reactant or product in unit time. To be more specific, it can be expressed in terms of: (i) the rate of decrease in the concentration of any one of the reactants, or (ii) the rate of increase in concentration of any one of the products. Consider a hypothetical reaction, assuming that the volume of the system remains constant. R → P
Read More: Chemical Kinetics MCQ
Factors Affecting The Reaction Rate:
- The concentration of Reactants - According to collision theory, which is discussed later, reactant molecules collide with each other to form products.
- Nature of the Reactants - The reaction rate also depends on the types of substances that are reacting.
- Physical State of Reactants - The physical state of a reactant whether it is solid, liquid, or gas can greatly affect the rate of change.
- Surface Area of Reactants - When two or more reactants are in the same phase of fluid, their particles collide more often than when either or both are in the solid phase or when they are in a heterogeneous mixture. In a heterogeneous medium, the collision between the particles occurs at an interface between phases. Compared to the homogeneous case, the number of collisions between reactants per unit time is significantly reduced, and so is the reaction rate.
- Temperature - If the temperature is increased, the number of collisions between reactant molecules per second. Increases, thereby increasing the rate of the reaction.
- Effect Of Solvent - The nature of the solvent also depends on the reaction rate of the solute particles.
- Catalyst - Catalysts alter the rate of the reaction by changing the reaction mechanism.