1. Accurately weigh out 0.03g of finely ground fertilizer into a 100ml beaker
2. Add about 20ml of boiling water and stir to dissolve powder
3. Transfer mixture into 250ml volumetric flask. Add water to make 250ml of solution. Transfer solution to 600ml beaker and stir to ensure concentration is uniform.
4. Dilute the fertilizer solution by factor of 10. Pour 25ml of the solution into a 250ml volumetric flask; add water to make 250ml solution.
5. Label 6 test tubes: 10mgL-1, 7.5 mgL-1, 5.0 mgL-1, 2.5 mgL-1, 0.0 mgL-1 and unknown.
6. Place 20ml of the diluted fertilizer solution into the “unknown” test tube.
7. Use a 10ml measuring cylinder to add standard phosphate solution and water to the labeled test tubes as per table below.
|Test tube label (mgL-1) Volume of 10mgL-1 Standard Phosphate solution (ml) Volume of Water |
|10.0 20 0 |
|7.5 15 5 |
|5.0 10 10 |
|2.5 5 15 |
|0.0 0 20 |
8. Add 2ml of ammonium molybate reagent and some crystals of ascorbic acid to each of the test tubes. Stir to dissolve the crystals.
9. Place all six test tubes in a 600ml beaker containing 200ml boiling water. Heat for 5 minutes. On heating the solutions should turn blue. Remove all test tubes and allow time to cool.
10. Compare the colour of the solution in the test tube labeled “unknown” with the colour standards to estimate the concentration of phosphate in the diluted fertilizer solution.
• Colour looked like 2.5gl-1QUESTIONS1.
The initial 250ml of fertilizer solution was diluted 10 times before being analyzed. What is the concentration of phosphate ions, in mg L-1, in the initial 250ml if fertilizer solution?2.
Use your answer to Q1 to find the mass of phosphorous ion the initial 250ml solution. This is the same as the mass of phosphorous in the sample of fertilizer
Calculate the percentage of phosphorous, by mass, in the fertilizer.
Sorry for the formatting, I'm a noob