If the first order reaction involves gaseous reactants and gaseous products the units of its rate are

Options

A. atm
B. atm-sec
C. atm `sec^(-1)`
D. `atm^(2)sec^(2)`

Explanation

To determine the units of the rate for a first-order reaction involving gaseous reactants and products, we can follow these steps:

### Step 1: Understand the Definition of Rate
The rate of a reaction is defined as the change in concentration of a reactant or product per unit time. Mathematically, it can be expressed as:
\[ \text{Rate} = -\frac{d[A]}{dt} \]
for a reactant A, where \([A]\) is the concentration of A.

### Step 2: Determine the Units of Concentration
For gaseous substances, concentration can be expressed in terms of pressure. The common unit for pressure in chemistry is atmospheres (atm). Therefore, the unit of concentration for a gas can be expressed as:
\[ \text{Concentration} = \text{Pressure} = \text{atm} \]

### Step 3: Determine the Units of Time
The time is typically measured in seconds (s).

### Step 4: Combine the Units to Find the Rate
Now, substituting the units of concentration and time into the rate equation:
\[ \text{Rate} = \frac{\text{atm}}{\text{s}} \]
Thus, the unit of the rate for a first-order reaction involving gaseous reactants and products is:
\[ \text{Rate} = \text{atm/s} \]

### Conclusion
The units of the rate for a first-order reaction involving gaseous reactants and products are **atm/s**.

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