At a temperature of `20^(@)C` , vapour pressure of water is 17.5 torr. If relative humidity is 45% , calculate the moles of water present in one litre of air at `20^(@)C`.

Explanation

To solve the problem, we need to calculate the moles of water present in one liter of air at 20°C, given the vapor pressure of water and the relative humidity. Here’s the step-by-step solution:

### Step 1: Calculate the Partial Pressure of Water Vapor
The relative humidity (RH) is defined as the ratio of the partial pressure of water vapor (P_H2O) to the vapor pressure of water (P_vapor) at a given temperature. This can be expressed mathematically as:

\[ \text{Relative Humidity} = \frac{P_{H2O}}{P_{vapor}} \times 100 \]
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