A technician needs to determine the concentration of lead ions in a sample of water
a) Suggest a test chemical that can be added to the water sample to preciitate the lead ions. Show a chemical euation for the formation of the precipitate
b) after a precipitate forms, it is filtered and the mass of the dry precipitate is measured. This informationis used to determine the concentrationof lead. Comment on the accuracy of the test. Suggest and explain a potential source of error
Could you please tell me what will form the precipitate and how the equation would unfold.
Thanks
a) To precipitate lead ions from a water sample, a common test chemical that can be used is sodium sulfate (Na2SO4). The chemical equation for the formation of the precipitate is:
Pb2+(aq) + SO4^2-(aq) → PbSO4(s)
In this reaction, lead ions (Pb2+) from the water sample react with sulfate ions (SO4^2-) provided by sodium sulfate to form lead sulfate (PbSO4), which is a precipitate.
b) Measuring the mass of the dry precipitate can be used to determine the concentration of lead ions. The accuracy of this test can be quite good if conducted properly. By knowing the mass of the precipitate and the volume of the original water sample, it is possible to calculate the concentration of lead ions.
One potential source of error in this test is incomplete precipitation, where not all the lead ions in the sample may precipitate out. This can lead to an underestimation of the lead concentration. To minimize this error, it is important to ensure the reaction goes to completion by providing an excess of the test chemical (sodium sulfate) and allowing enough time for the precipitate to form and settle before filtering.
Additionally, there could be impurities present in the water sample that interfere with the precipitation process or contribute to the weight of the precipitate. To account for this, it is important to properly analyze and interpret the results, considering any potential sources of error and using appropriate calibration standards for comparison.