State the formula relating pressure of a gas with its mole fraction in a liquid solution in contact with it.

Explanation

To state the formula relating the pressure of a gas with its mole fraction in a liquid solution in contact with it, we can refer to Henry's Law. Here is the step-by-step solution:

**Step 1: Understand Henry's Law**
Henry's Law states that the amount of gas that dissolves in a liquid at a given temperature is proportional to the partial pressure of that gas above the liquid.

**Step 2: Express the relationship**
According to Henry's Law, the pressure (P) of the gas is directly proportional to the mole fraction (x) of the gas in the liquid solution. This can be expressed mathematically as:
\[ P \propto x \]
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