Question

Sodium tripolyphosphate is mainly used in

• A. Plastics
• B. Detergents formulation
• C. Mechanical industries
• D. Fertilizers

Hint:

STPP = Detergent Builder. It deactivates hard-water minerals ($\text{Ca}^{2+}$, $\text{Mg}^{2+}$) through chelation, allowing the main surfactant molecules to work efficiently at removing oil and dirt.

Answer 1

The Correct Option is B

Concept: Sodium Tripolyphosphate ($\text{Na}_5\text{P}_3\text{O}_{10}$), abbreviated as STPP, is an inorganic polyphosphate salt.

Step 1: Explaining its primary application in chemical formulations.
The major industrial application of sodium tripolyphosphate is as a key builder component in commercial laundry and dishwashing detergent formulations.

Step 2: Explaining its chemical mechanism as a builder.
Hard water contains dissolved divalent metal cations, primarily $\text{Ca}^{2+}$ and $\text{Mg}^{2+}$, which react with surfactant compounds to form insoluble scum, severely reducing cleaning efficiency. STPP functions as a highly effective chelating and sequestering agent: \[ \text{Na}_5\text{P}_3\text{O}_{10} + \text{Ca}^{2+} \rightarrow \big[\text{Na}_3\text{CaP}_3\text{O}_{10}\big] + 2\text{Na}^+ \] By binding these hardness ions into water-soluble coordinate complexes, STPP prevents them from interfering with the detergents. It also helps suspend soil particles in the wash water, preventing them from redepositing onto clothing. This aligns with option (2).