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13 Dec 2019

What mass of (NH4)2Fe(SO4)2*2 H2O (Solid) is required to preparea 500mL solution containing 100 ppm in Fe? 2. Using this stocksolution, what aliquot must be used to prepare calibrationsolutions, 100-mL volumes, of the following: (a) 0.100 ppm, (b)0.500 ppm, (c) 2.00 ppm, (d) 4.00 ppm and (e) 7.0 ppm.

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I need help with question 2

Lab 5. Determination of iron in a supplement tablet by atomic Prelab Helpful Reading: Discussion of atomic absorption spectrometry: The introduction to Chapter 21, section 21-1 and the part describing flames at the beginning of section 21-2 In this lab a flame atomic absorption spectrometer will be used to determine the amount of Fe in a vitamin pill. You may select your sample from one of the pills containing -9 mg/pil, Women's spectrometer detects following three types of pills: Energy Vitamin s Vitamin pills containing 18 mg/pill. The atomic absorption Fe well when the Fe concentration is between 1.25ppm and 5ppm Answer the following prelab questions: 1. A. How will you prepare your calibration solutions? You will use five calibration solutions in this lab, including the blank. A stock iron solution for atomic absorption spectroscopy will be made available to you that has a concentration of 1000 ppm (w/v) Fe. For an iron analysis the Varian atomic absorption spectrometer in the quant lab-requires samples with concentrations between 1.25 and 5 ppm (w/v) and a blank. You will prepare 5 calibration solutions, having respectively, the following final concentrations of Fe: 0, 1.25, 2.5, 3.5 and 5 ppm (w/v) Fe. These solutions will be prepared by diluting an appropriate number of microliters of 1000ppm (w/v) Fe with DI water in a 100 ml volumetric flask. Calculate how many microliters of stock iron solution are needed to prepare calibration solutions at the concentrations mentioned above. 2. How will you prepare your sample for analysis? Draw up one experimental plan for diluting your chosen pill to an appropriate concentration for the atomic absorption instrument using a micropipette. Specifically a. Which pill, from the two types mentioned above do you propose to analyze? How many mg of Fe is the pill expected to have? Assume that you will digest a vitamin pill as you did last week, and will dilute the digest to 100ml-this solution will be called vitamin solution 1 (VS1). You willuse a micropipette to transfer some liquid from VS1 to another 100mL volumetric flask and b. will ilute this to the mark. This second solution, vitamin solution 2 (VS2) will be the sample that you measure. What volume should be transferred from sample solution 1 to sample solution 2 with the micropipette? Draw a picture to illustrate your dilution scheme. Write out a sample preparation equation relating the estimated concentration in the mg/pll (based on the label) to the estimated concentration (in units of ppm) of Fe in the sample that will be measured. Do this in your lab notebook. c. d. Lab 5 Determination of iron/atomic absorption spectroscopy 31

Answer/solve for the following:

1. Using an automatic pipet, a student measured 450 mL of an unknown liquid which weighed 0.631 g. What is the density of this liquid? Circle the correct answer. You must show your math (including all units) for full credit.

(a) 0.0801 g/mL

(b) 0.0140 g/mL

(d) 1.40 g/mL

A student was given 2.8 g of an unknown solid. The student only used 1.1 g of that unknown solid to perform the recrystallization. Following the recrystallization, the student recovered 0.63 g of the unknown solid. Calculate the percent recovery. Circle the correct answer. You must show your math (including all units) for full credit.

(a) 43 %

(b) 190 %

(d) 57 %

(e) 233 %

3. Tell how to prepare the following solutions:

a) 250mL of a 50.0 ppm solution of Ni from pure solid NiCl2 6H2O (FW=237.71 g/mol)

b) 500mL of a 0.01000M EDTA from the pure solid (FW=372.23 g/mol)

Solve the above completely showing all of your work so I can see how you derived answers.

Thanks!

7. Complete the following table:

Element Moles Mass Num

7. Complete the following table:

Element Moles Mass Number of molecules

13. It is the component that is in a solution, in smaller quantity.

a. Solution

b. Solvent

c. Solvent

d. Soluto

14. It is the component that is in a solution in greater quantity.

a. Solution

b. Solvent

c. Solvent

d. The answers b and c are correct.

15. The quantitative expression of the dissolved amount of solute in a quantity determined solvent is known as:

a. Solution

b. Volume

c. Concentration

d. Stoichiometry

16.Express the moles of solute among the liters of solution

a. Molality

b. Molarity

c. % weight by volume

d. % weight by weight

17.Express the moles of solute between kg of solvent

a. Molarity

b. ppm

c. ppt

d. Molality

18. What is the molarity of a solution prepared by dissolving 7.50 g of nitrate of magnesium, Mg (NO3) 2 in enough water to prepare 25.0 mL of solution?

a. 10.3 M

b. 5.6 M

c. 6.5 M

d. 2.03 M

19. How many grams of sodium chloride, NaCl are needed to prepare 125 mL of 0.037 M NaCl solution

a. 1.021 M

b. 0.268 M

c. 0.201 M

d. 0.500 M

20. Calculate the molality of a solution containing 12.5 g of ethylene glycol (C2H6O2) dissolved in 135 g of water.

21. A solution of ethylene glycol contains 21.2 g of ethylene glycol (C2H6O2) in 85.4 mL of water. Calculate the freezing point and the boiling point of the solution. (Assume the water density is 1.00 g / mL)

22. At what volume should you dilute 75 mL of a 10.0 M solution of H2SO4 to obtain a 1.75 M solution of H2SO4.

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