Bhoooootnike de Chemistry Questions

[Bhootnike]

Hallo.
I wanting to ask the following:


~from chem dimensions worksheet.

"A 2.890 g sample of steel was analysed for its manganese content in the following manner.
The sample was dissolved in concentrated nitric acid, producing manganese(II) ions.
Potassium persulfate, K2S2O8, was added to remove the carbon in the steel. This oxidised the carbon to carbon dioxide.
The virtually colourless manganese(II) ions were converted to deep purple permanganate (MnO4–) ions by boiling with a solution containing periodate (IO4–) ions. In this reaction the periodate ions are converted to IO3– ions.
Phosphoric acid was added in order to convert the yellow iron(III) ions to a colourless complex (so the iron ions would not interfere with the colorimetric MnO4– ion analysis).
The solution was diluted with distilled water to 1.00 L in a volumetric flask.
A series of standards was prepared, containing MnO4– ranging from 1.00 to 8.00 ppm.
The colorimeter was set to measure absorbance at 520 nm, and calibrated using a solvent blank. The absorbances of the standard solutions and the steel sample were taken and are given in the table below.

table: bla bla bla"

questions:
7 ) As well as water, what else should be added to the standards and the solvent blank and why?
8 ) Why was 520 nm a more appropriate wavelength than 400 nm for this analysis?
9 ) During calibration, the absorbance was set to zero using a solvent blank. Would your calculated percentage of Mn (m/m) have been affected had this not been done? Explain.


thanking you, sincerely, may the curry be with you.

[Bhootnike]

Are we required to know the detectors involved in column chromatography? e.g. thermal conductivity, electron capture.. etc ?

[Mao]

Are we required to know the detectors involved in column chromatography? e.g. thermal conductivity, electron capture.. etc ?

No.

[Bhootnike]

sweet! thanks Mao

Anyone got any idea on the question in the first post, i.e solvent blank ?

[Bhootnike]

E1.
Solids are not injected into the inlet port of a gas chromatograph. How might the chromatograms of the chips have been obtained?
AE1.
A sample of air from near the chips may have been injected into the inlet port of the gas chromatograph. Alternatively, the chips may have been mashed and mixed with a solvent that would cause the compounds responsible for the off-flavours to dissolve; this solution would then have been injected into the instrument.

So.. i said that the solid sample could have heated until vapours of the volatile organic compounds were produced, which where then injected into port and analysed for the compounds responsible for off-flavours.
Am i still correct?