The mole fraction of water in a solution of HCI is 0.78. Calculate the molality of the solution.

Explanation

To calculate the molality of the HCl solution given that the mole fraction of water is 0.78, we can follow these steps:

### Step 1: Understand the Definitions
- **Mole Fraction (X)**: The mole fraction of a component in a solution is defined as the number of moles of that component divided by the total number of moles of all components in the solution.
- **Molality (m)**: Molality is defined as the number of moles of solute per kilogram of solvent.

### Step 2: Calculate the Mole Fraction of HCl
Given that the mole fraction of water (H2O) is 0.78, we can find the mole fraction of HCl (X_HCl):
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