The term `(-(dc)/(dt))` in a rate equation refers to the :

Options

A. Concentration of the reactant
B. Decrease in concentration of the reactant with time
C. Increase in concentration of the reactant with time
D. Velocity constant of the reaction

Answer

To solve the question regarding the term `(-(dc)/(dt))` in a rate equation, we can break it down step by step:

### Step-by-Step Solution:

1. **Understanding the Rate of Reaction**:
The rate of a chemical reaction is expressed in terms of the change in concentration of reactants and products over time. In a general reaction, we can represent it as:
\[ aA + bB \rightarrow cC + dD \]
where A and B are reactants, and C and D are products.

2. **Differential Rate Law**:
The differential rate law describes how the concentration of reactants and products changes with time. For reactants, as the reaction proceeds, their concentrations decrease. For products, their concentrations increase.

3. **Expressing Changes in Concentration**:
For a reactant A, the change in concentration over time can be expressed as:
\[ -\frac{d[A]}{dt} \]
This negative sign indicates that the concentration of A is decreasing as the reaction progresses.

4. **Applying to the Given Term**:
The term `-(dc)/(dt)` specifically refers to the change in concentration of a substance C over time. The negative sign indicates that the concentration of C is decreasing if C is a reactant.

5. **Identifying the Meaning of the Term**:
Therefore, `-(dc)/(dt)` represents the rate at which the concentration of reactant C decreases with respect to time. This is a common way to express the rate of consumption of a reactant in a chemical reaction.

6. **Conclusion**:
The term `-(dc)/(dt)` in a rate equation refers to the **decrease in concentration of the reactant C with respect to time**.