Reaction Kinetics: Rate, Rate Constants, and Order

Reaction kinetics rate rate constants and order describe how drug concentration changes over time in pharmaceutical chemistry.

Basic Concepts of Reaction kinetics rate rate constants and order

1. Rate of Reaction:

   • Measures how fast reactants are converted into products. Influenced by temperature, concentration, catalysts, and surface area.

2. Rate Constant (k):

   • A constant specific to a given reaction at a certain temperature.

3. Order of Reaction:

   • Indicates how the reaction rate depends on the concentration of reactants.

General Rate Equation:

• For a reaction:
• aA + bB → Products
• $\text{Rate} = k [A]^m [B]^n$
• m & n: Orders of the reaction with respect to A and B, respectively.
• Overall Reaction Order = m + n

Types of Reaction Kinetics

1. Zero-Order Kinetics

   • Rate is independent of reactant concentration.
   • Drug concentration decreases linearly over time.

   • Rate Equation:

   • Rate = k

   • Half-life (t₁/₂):

     • $t_{1/2} = \frac{[A]_0}{2k}$
     • Half-life depends on initial concentration.

2. First-Order Kinetics

   • • Rate is directly proportional to the concentration of the drug.
     • Drug elimination follows an exponential decline.

   • Rate Equation:

   • Rate = k[A]

   • Half-life (t₁/₂):

     • $t_{1/2} = \frac{0.693}{k}$
     • Half-life is constant, regardless of concentration.

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