ate Checked: Pre-lab Worksheet: Spectrophotometric Determination of Trace Amount
ID: 863060 • Letter: A
Question
ate Checked: Pre-lab Worksheet: Spectrophotometric Determination of Trace Amounts of Iron in a Vitamin Tablet Read the experiment, and then answer the following questions. Show all calculations; attach additional pages as needed 1. Calculate the amount of ferrous ammonium sulfate hexahydrate (FAS), Fe(NHSO 6H0, (392.14 g/mole) needed to prepare 250 mL of 100 ppm of Fe. 2. What volumes of 100 ppm iron solution should be diluted to prepare the following solutions? Enter your answers here; attach additional pages to show the calculations. a) 200 mL of 0.5 ppm Fe? b) 100 mL of 1, 2, 3 and 4 ppm Fe? Suppose instead of weighing out the mass you calculated in question 1, you weighed out 0.1954 g of ferrous ammonium sulfate hexahydrate. Determine the exact concentrations of the stock (-100 ppm) and diluted solutions. Show answers here; attach additional pages to show the calculations. 3. Linear regression of the calibration data yields a best-fit line with the equation: y = 0.25x + 0.10. If the absorbance of your diluted unknown solution is 0.467, what is the concentration (ppm) of Fe 4, 46Explanation / Answer
1) we need to prepare 100ppm of Fe which is equal to = 100mg / 1L
so in 250 mL amount of Fe = 25mg
Mol wt of ferrous ammonium sulphate = 392.14
in 392.14 g of ferrous ammonium sulphate = 55.8 g
so for 25mg of iron we need = 175.68 mg of ferrous ammonium sulphate.
2)
a) M1V1 = M2V2
100ppm X V1 = 0.5 X 200mL
V1= 1mL of solution will be needed
b) 1ppm
M1V1 = M2V2
100ppm X V1 = 1X 100mL
V1= 1mL of solution will be needed
For 2ppm
M1V1 = M2V2
100ppm X V1 = 2X 100mL
V1= 2mL of solution will be needed
For 3 ppm
M1V1 = M2V2
100ppm X V1 = 3X 100mL
V1= 3mL of solution will be needed
for 4ppm
M1V1 = M2V2
100ppm X V1 = 4X 100mL
V1= 4mL of solution will be needed
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