The strength of an aqueous NaOH solution is most accurately determined by titrating: (Note: consider that an appropriate indicator is used)

Options

A. (a) Aq. NaOH is a volumetric Flask and concentrated `H_(2)SO_(4)` in a conical Flask.
B. (b) Aq. NaOH in a burette and concentrated `H_(2)SO_(4)` in a conical Flask.
C. (c) Aq. NaOH in a burette and aqueous oxalic acid in a conical Flask.
D. (d) Aq. NaOH in a pipette and aqueous oxalic acid in a burette.

Answer

To determine the strength of an aqueous NaOH solution accurately, we need to perform a titration with a suitable acid. The best option among the given choices is to titrate NaOH with aqueous oxalic acid. Here’s a step-by-step solution to arrive at the correct answer:

### Step-by-Step Solution:

1. **Understanding the Solutions**:
- NaOH is a strong base, and we need to titrate it with an acid to determine its concentration.
- A primary standard is a substance that can be used to determine the concentration of another substance through titration. It should have a known concentration and should not change over time.

2. **Identifying the Options**:
- **Option A**: Aqueous NaOH in a volumetric flask and concentrated H2SO4 in a conical flask.
- **Option B**: Aqueous NaOH in a burette and concentrated H2SO4 in a conical flask.
- **Option C**: Aqueous NaOH in a burette and aqueous oxalic acid in a conical flask.
- **Option D**: Aqueous NaOH in a pipette and aqueous oxalic acid in a burette.

3. **Analyzing Each Option**:
- **Option A**: This option cannot be used for titration as a volumetric flask is not suitable for dispensing the titrant.
- **Option B**: While NaOH is in the burette, H2SO4 is a secondary standard and its concentration can vary over time, making it unsuitable for accurate titration.
- **Option C**: Aqueous NaOH in the burette and aqueous oxalic acid in the conical flask. Oxalic acid is a primary standard, making this option suitable for accurate titration.
- **Option D**: Using a pipette for NaOH is not appropriate for titration; a burette is required for accurate measurement of the titrant.

4. **Conclusion**:
- The best choice for accurately determining the strength of an aqueous NaOH solution is **Option C**: Aqueous NaOH in a burette and aqueous oxalic acid in a conical flask.

### Final Answer:
**Option C: Aqueous NaOH in burette and aqueous oxalic acid in conical flask.**