For what type of the following reactions is the law of mass action, never obeyed?

Options

A. Zero order
B. Firt order
C. Second order
D. Third order

Answer

To solve the question "For what type of the following reactions is the law of mass action never obeyed?", we need to understand the concept of the law of mass action and its relation to reaction orders.

### Step-by-Step Solution:

1. **Understanding the Law of Mass Action**:
The law of mass action states that the rate of a chemical reaction is proportional to the product of the active masses (concentrations) of the reactants, each raised to a power equal to the coefficient of that substance in the balanced chemical equation.

2. **Identifying Reaction Orders**:
Reactions can be classified based on their order, which indicates how the rate of reaction depends on the concentration of reactants. Common orders include zero-order, first-order, second-order, etc.

3. **Zero-Order Reactions**:
In a zero-order reaction, the rate of reaction is constant and does not depend on the concentration of the reactants. The rate law expression for a zero-order reaction can be written as:
\[ R = k[A]^0 = k \]
Here, [A] is the concentration of the reactant, and since any number raised to the power of zero is one, the rate (R) becomes equal to the rate constant (k) and is independent of the concentration of reactants.

4. **Conclusion**:
Since the rate of a zero-order reaction does not depend on the concentration of reactants, the law of mass action is not obeyed for zero-order reactions. Therefore, the answer to the question is that the law of mass action is never obeyed in zero-order reactions.

### Final Answer:
The law of mass action is never obeyed for zero-order reactions.

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