Question

Pure solid NaH₂PO₄ is dissolved in distilled water, making 100.00 ml of solution. 10.00ml of this solution is diluted to 100.00 ml to prepare the original phosphate standard solution. Three working standard solutions are made from this by pipetting 0.8ml, 1.5ml and 3.0 ml of the original standard solution into 100.00 ml volumetric flasks. Acid and molybdate reagent are added and the solutions are diluted to 100.00 ml.

You may assume that all these absorbance measurements have already been corrected for any blank absorbance.

The absorbance of each is measured in the spectrophotometer.

Mass of NaH₂PO₄ (mg) 512.2
Absorbance Standard 1 (0.8 ml) 0.1922
Standard 2 (1.5 ml) 0.3604
Standard 3 (3.0 ml) 0.7209

Concentration of Standard 1(mM)