Let P and `P_(s)` be the partial pressure of `H_(2)O(g)` and vapour pressure of `H_(2)O(l)` respectively. Then the % relative humidity is given by:

Options

A. `(P_(s)+P)/(P_(s))xx100`
B. `(P)/(P_(s))xx100`
C. `(P_(s))/(P)xx100`
D. `(P+P_(s))xx100`

Explanation

To find the percentage relative humidity, we can follow these steps:

### Step 1: Understand the Definitions
- **Partial Pressure of H₂O (P)**: This is the pressure exerted by the water vapor in the air.
- **Vapor Pressure of H₂O (Pₛ)**: This is the pressure exerted by the water vapor when the liquid water is in equilibrium with its vapor at a given temperature.

### Step 2: Write the Formula for Relative Humidity
The formula for percentage relative humidity is given by:

\[ \text{Relative Humidity (\%)} = \left( \frac{P}{P_s} \right) \times 100 \]

Where:
- \( P \) = Partial pressure of water vapor (H₂O gas)
- \( P_s \) = Vapor pressure of water (H₂O liquid)

### Step 3: Substitute the Values
In this case, we don't have specific numerical values for \( P \) and \( P_s \), but we can express the relative humidity in terms of these variables:

\[ \text{Relative Humidity (\%)} = \left( \frac{P}{P_s} \right) \times 100 \]

### Step 4: Conclusion
Thus, the percentage relative humidity is calculated using the formula:

\[ \text{Relative Humidity (\%)} = \frac{P}{P_s} \times 100 \]

This means that if you know the partial pressure of water vapor and the vapor pressure of liquid water, you can easily calculate the relative humidity.