1. KHP is a Primary Standard:
* Stable: KHP is a solid that doesn't readily absorb moisture or react with the atmosphere, making it very stable. This means its purity remains consistent over time.
* High Purity: KHP can be purchased in very high purity, ensuring accurate and precise measurements.
* Known Molecular Weight: KHP has a well-defined and accurate molecular weight, which is crucial for calculations.
2. KHP Reacts Completely with NaOH:
* Acid-Base Reaction: KHP is a monoprotic acid, meaning it has one acidic hydrogen atom that reacts with the hydroxide ions (OH-) in NaOH in a 1:1 stoichiometric ratio. This means for every mole of KHP, you need exactly one mole of NaOH for complete neutralization.
3. KHP Provides a Clear Endpoint:
* Color Change: When NaOH is added to KHP solution, the solution will change color at the equivalence point (when the moles of acid and base are equal). This color change is usually observed using a suitable indicator like phenolphthalein, which turns pink in basic solutions.
In summary:
KHP is used to standardize NaOH solutions because it's a stable, highly pure primary standard with a known molecular weight that reacts completely and provides a clear endpoint in titration. This allows you to accurately determine the concentration of the NaOH solution for use in other experiments.
