Nitrate nitrogen in water is determined by reacting with phenoldisulfonic acid to give a yellow color with an absorption maximum at 410 nm. A 100-mL sample that has been stabilized by adding 0.8MLH,SO/L is treated with silver sulfate to precipitate chloride ion, which interferes. The precipitate is filtered and washed (washings added to filtered sample). The sample solution is adjusted to pH 7 with dilute NaOH and evaporated just to dryness. The residue is treated with 2.0mL phenol disulfonic acid solution and heated in a hot-water bath to aid dissolution. Twenty milliliters of distilled water and 6mL ammonia are added to develop the maximum color, and the clear solution is transferred to a 50-mL volumetric flask and diluted to volume with distilled water. A blank is prepared using the same volume of reagents, starting with the disulfonic acid step. A standard nitrate solution is prepared by dissolving 0.722 g anhydrous KNO3 and diluting to 1 L. A standard addition calibration is performed by spiking a separate 100-mL portion of the sample with 1.00ml of the standard solution and carrying through the entire procedure. The following absorbance readings were obtained: blank, 0.032; sample, 0.270; sample plus standard, 0.854. What is the concentration of nitrate nitrogen in the sample in parts per million?
Nitrate nitrogen in water is determined by reacting with phenoldisulfonic acid to give a yellow color with an absorption maximum at 410 nm. A 100-mL sample that has been stabilized by adding 0.8MLH,SO/L is treated with silver sulfate to precipitate chloride ion, which interferes. The precipitate is filtered and washed (washings added to filtered sample). The sample solution is adjusted to pH 7 with dilute NaOH and evaporated just to dryness. The residue is treated with 2.0mL phenol disulfonic acid solution and heated in a hot-water bath to aid dissolution. Twenty milliliters of distilled water and 6mL ammonia are added to develop the maximum color, and the clear solution is transferred to a 50-mL volumetric flask and diluted to volume with distilled water. A blank is prepared using the same volume of reagents, starting with the disulfonic acid step. A standard nitrate solution is prepared by dissolving 0.722 g anhydrous KNO3 and diluting to 1 L. A standard addition calibration is performed by spiking a separate 100-mL portion of the sample with 1.00ml of the standard solution and carrying through the entire procedure. The following absorbance readings were obtained: blank, 0.032; sample, 0.270; sample plus standard, 0.854. What is the concentration of nitrate nitrogen in the sample in parts per million?
Chapter10: Potentiometry And Redox Titrations
Section: Chapter Questions
Problem 8P
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Transcribed Image Text:Nitrate nitrogen in water is determined by reacting with phenoldisulfonic acid to give a yellow color with an
absorption maximum at 410 nm. A 100-mL sample that has been stabilized by adding 0.8MLH,SO/L is treated
with silver sulfate to precipitate chloride ion, which interferes. The precipitate is filtered and washed (washings
added to filtered sample). The sample solution is adjusted to pH 7 with dilute NaOH and evaporated just to
dryness. The residue is treated with 2.0mL phenol disulfonic acid solution and heated in a hot-water bath to aid
dissolution. Twenty milliliters of distilled water and 6mL ammonia are added to develop the maximum color,
and the clear solution is transferred to a 50-ml volumetric flask and diluted to volume with distilled water, A
blank is prepared using the same volume of reagents, starting with the disulfonic acid step. A standard nitrate
solution is prepared by dissolving 0.722 g anhydrous KNO3 and diluting to 1 L. A standard addition calibration is
performed by spiking a separate 100-ml portion of the sample with 1.00mL of the standard solution and
carrying through the entire procedure. The following absorbance readings were obtained: blank, 0.032; sample,
0.270; sample plus standard, 0.854.
What is the concentration of nitrate nitrogen in the sample in parts per million?
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