In my assignment I've been given two water samples from the hinze dam. The first sample has been untouched, however the second has been contaminated with an unknown ionic compound. To identify the unknown contaminant, multiple tests were done, namely ISE tests and a TDS test.
The results were as follows
Nitrate test – Nitrate ISE with an accuracy of ±10% full scale (calibrated 1 to 100 mg/L) and a range of 1mg/L to 14,000 mg/L
Pre-contamination sample – 3mg/L
Post-contamination sample – 2000mg/L
Ammonium test – Ammonium ISE with an accuracy of ±10% full scale (calibrated 1 to 100 mg/L) and a range of 1mg/L to 18,000 mg/L
Pre-contamination sample – 0.1mg/L
Post-contamination sample – 0.2mg/L
Calcium test – Calcium ISE with an accuracy of ±10% full scale (calibrated 10 to 1000 mg/L) and a range of 1mg/L to 40,000 mg/L
Pre-contamination sample – 10.8mg/L
Post-contamination sample 2.8mg/L
Chloride test – Chloride ISE with an accuracy of ±10% full scale (calibrated 10 to 1000 mg/L) and a range of 2mg/L to 35,000 mg/L
Pre-contamination sample – 67mg/L
Post-contamination sample – 316mg/L
Phosphate test – colorimeter test using a reagent that turns the solution blue using a 10mg/L standard and a 0mg/L standard (distilled water)
Pre-contamination sample – 2.3mg/L
Post-contamination sample – 0.56mg/L
TDS test with 200mL of post and pre contamination solutions. Water was poured through filter paper into beakers and the beakers baked in an oven, then the weight of the new solids in the beakers weighed.
Pre-contamination sample – 0.02g
Post-contamination sample – 3.89g
Conducting a flame test on the post-contamination sample's TDS provided an orange flame, which indicated that part of the compound was sodium.
Since the TDS indicated an excess of sodium and the ISE tests indicated an excess of nitrate, the pollutant is likely sodium nitrate.
If the pollutant is sodium nitrate, why did the ions ammonium (although negligible)and chloride increase after contamination, when the other ions calcium and phosphate decreased?
So far I believe that the calcium decreased as it bonded with the dissociated nitrate.
Also, i think that the phosphate decreased as the dissociated increased sodium levels bonded with it.
However, I believe the decrease in calcium should cause the chloride to increase as the presence of calcium chloride would have its equilibrium shift in a way as to create for chloride as calcium is reduced. Which isn’t supported by the data?
Does solubility affect how the ions change?