Labs 5-8

Question 1

At what wavelength do you use to look at Si?

Answer 1

410nm

Question 2

What are the reagents used in silicic acid analysis?

Answer 2

3N hydrochloric acid, ammonium molybdate reagent, oxalic acid solution, silicic acid primary stock standard, silicic acid working stock standard

Question 3

How were the silic acid standard made?

Answer 3

Use varying volumes of 500uM silicic acid standard with 3.2% NaCl and add reagent, HCl and oxalic acid

Question 4

What does the ammonium molybdate do?

Answer 4

Has low pH and reacts with dissolved silicon and phosphate to produce coloured complexes to be measured with visible spectrophotometry

Question 5

How do you create a calibration curve?

Answer 5

Plot the concentration of the standards on the x-axis and the absorbance at the wavelength on the y axis

Question 6

At what wavelength do you look at phosphate?

Answer 6

880nm

Question 7

What are the reagents used in phosphate analysis?

Answer 7

Mixed reagent (Molybdic acid, ascorbic acid and trivalent antimon, sulphuric acid), phosphate primary/working stock

Question 8

What coloured complex is formed in phosphate analysis?

Answer 8

Phosphomolybdenum blue complex

Question 9

How are the phosphate standard prepared?

Answer 9

Mixing various volumes of the 50uM phosphate standard with various volumes of 3.2% NaCl

Question 10

What reagents were used in chlorophyll analysis?

Answer 10

Acetone, HCl

Question 11

At what wavelength is nitrate analyzed?

Answer 11

540nm

Question 12

What reagents are used in nitrate analysis?

Answer 12

Colour reagent B, ammonium chloride, nitrate stock, spongy cadmium

Question 13

How are nitrate standards formed?

Answer 13

Mix varying volumes of nitrate standard with varying volumes of NaCl