When a standard solution of NaOH is left in air for a few hours:

Options

A. A precipitate will form
B. Strength will decrese
C. Strength will increse
D. The concentration of `Na^(o+)` ions will remain constant

Explanation

To solve the question regarding what happens when a standard solution of NaOH is left in air for a few hours, we can follow these steps:

### Step-by-Step Solution:

1. **Understanding the Nature of NaOH**:
- Sodium hydroxide (NaOH) is known to be deliquescent, which means it has the ability to absorb moisture from the air.

**Hint**: Recall the properties of deliquescent substances and how they interact with moisture in the environment.

2. **Effect of Absorbing Water**:
- When NaOH absorbs water from the atmosphere, it increases the amount of water in the solution. This addition of water dilutes the solution.

**Hint**: Think about how adding more solvent (water) to a solution affects its concentration.

3. **Concentration and Strength**:
- The strength of a solution refers to the amount of solute (in this case, NaOH) present in a given volume of solution. As water is absorbed, the concentration of NaOH decreases because the same amount of NaOH is now in a larger volume of solution.

**Hint**: Concentration is calculated as moles of solute per liter of solution. Consider how the volume change affects this calculation.

4. **Conclusion**:
- Since the strength of the NaOH solution decreases due to the absorption of water, the correct answer to the question is that the strength of the solution will decrease.

**Hint**: Review the definitions of strength and concentration to ensure clarity on how they relate to each other in this context.

### Final Answer:
The strength of the NaOH solution will decrease when it is left in the air for a few hours.