Mole fraction of NaOH in an aqueous solution is 0.3. Mole fraction of water is __________ .

Answer

To find the mole fraction of water in an aqueous solution where the mole fraction of NaOH is given as 0.3, we can follow these steps:

### Step-by-Step Solution:

1. **Understanding Mole Fraction**:
- The mole fraction of a component in a solution is defined as the ratio of the number of moles of that component to the total number of moles of all components in the solution.
- The sum of the mole fractions of all components in a solution is always equal to 1.

2. **Identify Components**:
- In this case, we have two components: NaOH (solute) and water (solvent).
- Given: Mole fraction of NaOH (X_NaOH) = 0.3.

3. **Use the Mole Fraction Relationship**:
- According to the mole fraction relationship:
\[ X_{NaOH} + X_{water} = 1 \]
- Where \(X_{water}\) is the mole fraction of water.

4. **Substituting the Known Value**:
- Substitute the value of the mole fraction of NaOH into the equation:
\[ 0.3 + X_{water} = 1 \]

5. **Solving for Mole Fraction of Water**:
- Rearranging the equation to find \(X_{water}\):
\[ X_{water} = 1 - 0.3 \]
- Calculate:
\[ X_{water} = 0.7 \]

6. **Conclusion**:
- Therefore, the mole fraction of water in the solution is 0.7.

### Final Answer:
The mole fraction of water is **0.7**.

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