The method of standard additions was used to determine nitrite in a soil sample. An aliquot of 1.00mL of the sample was mixed with 24mL of a colorimetric reagent, and the nitrite was converted to a color product with a blank-corrected absorbance of 0.300. To 50mL of the original sample, 1.00mL of a standard solution of 0.001M nitrite was added. the same color-forming procedure was followed and the new absorbance was 0.530. What was the concentration of nitrite in the original undiluted sample?

20.00ml of unknown sample is diluted to 250ml absorbance 0.2430. absorbance for 70.00 ppm standard is 0.95. what is ppm concentration in original undiluted sample?

thanks!!

The data below are for analysis of an unknown solution by the method of standard additions. 5.00 mL of unknown solution are added to 10-mL volumetric flasks, along with zero to 4 mL of a 14.4 mg/L standard solution. Then DI water is added to bring the volume up to 10.00 mL, the flasks are mixed well, and their absorbances are measured. A blank sample gave an absorbance of zero.

(a) Use only solutions 0 and 1 with the single-spike method of standard additions to calculate the concentration of the unknown. (Remember, this is asking for the concentration of the original unknown solution so you will have to account for the fact that 5.00 mL of unknown was diluted to 10.00 mL before absorbance was measured.)

mg/L

(b) Use all five solutions and the multi-spike (linear regression) method of standard additions to calculate the concentration of the unknown.

mg/L

Copper was determined in a river water sample by atomic absorption spectrometry and the method of standard additions. For the addition, 300.0 μL of a 1000.0-μg/mL standard was added to 250.0 mL of solution.

The following data were obtained: Absorbance of reagent blank = 0.020

Absorbance of sample = 0.580

Absorbance of sample plus addition - blank = 1.002 a

Calculate the copper concentration in the sample. Concentration = μg/mL