Environmental Science

2a) Which polyphosphate is commonly used in detergents and write a balanced chemical equation for the hydrolysis of this polyphosphate?

Sodium tri-polyphosphate (Na5P3O10) has been used widely as a constituent of laundry detergents, but there are others. Upon hydrolysis, various Sodium Hydrogen Phosphates are produced.

Na5P3O10 + 2 H2O --> NaH2PO4 + 2 Na2HPO4

The products are both called ortho phosphates. The first is Sodium dihydrogen phosphate and the other is Disodium hydrogen phosphate.

2b) Besides detergents what are the other main sources of phosphate ions found in natural water?

The other main sources of phosphate ions found in water are naturally in rocks and other mineral deposits. Through the natural process of weathering, the rocks release the phosphorus as phosphorus ions, also phosphorous can be naturally found in abundant areas of soil with high volcanic activities. In terms of man-made causes, agricultural runoffs where fertilizers are used also contribute to the presence of phosphorous in natural water.

3) In areas with very hard water, would you expect the concentration of dissolved phosphates to be higher or lower than in areas with soft waters? Explain.

The concentration of dissolved phosphate ions would be higher than in areas with soft water. Since hard water is water with high mineral content, which also contains phosphates, the concentration of dissolved phosphates would therefore be higher. For example, if hard water contains phosphate ions, after adding more phosphate ions, the concentration of the total phosphate ions would be higher.

Discussion

We are satisfied with our results. We obtained 1.152 for the absorbance against 2.1 x 10^-4 moles/L which is directly on the line of best fit which the spectrophotometer plotted for us. The results that we obtained were neither too high nor too low, so its precise.

We have taken all the precautions to prevent human errors such as reading from the base of the meniscus, pouring the solutions into the volumetric flask using a funnel to prevent spillage, while pouring the solution, we added dionised to dilute the solution and we made sure that we added the water just before the mark. Subsequently, we used a dropper to drop the final drops of deionized water to hit the mark of the volumetric flask. We rinsed the pipettes used with deionized water to remove any impurities, we then rinsed the pipette with the solution itself so that the concentration in the pipette would be constant. We ensured that we held the rough side of the quevette and cleaned the smooth sides with lint-free paper to prevent finger prints from interfering with the absorbance amount of the solution.