Please solve the problems below showing your work and how you derived the correc

Question

Please solve the problems below showing your work and how you derived the correct answer. I don't really understand the steps I need to take.

1. Describe how to prepare a 5.0% w/v solution of sodium chloride.

2. All grain contains an acceptable amount of rat hairs. If 40 rat hairs weighing 1.5x10-4 g each were found in a 1.00 kg sample of grain, what is the content of rat hairs in that sample expressed in ppm?

3. The concentration of lead in an industrial waste steam is 0.28ppm. What is its molar concentration?

Describe the preparation of 500 mL of a 0.1 N H2SO4 assuming that you have in stock 18.0 M H2SO4. You may assume that this solution will be used for an acid-base volumetric analysis. A spectroscopic method for determining albumin content in serum involves the preparation of a stock solution of albumin (6g/100mL aqueous solution). From the prepared stock, you need to prepare a series of working standard solutions. Assume reagent cost is a consideration so you plan to prepare a 1mL of each of these standards: 12, 24, 36, and 48 g/L. To complete this task you have 500 ?L and 1000?L automatic transfer pipets. Describe how you might prepare these standards.

Explanation / Answer

1)

5.0% w/v = 5 % of wt per volume

that is

5 grams of NaCl per 100 mL solution

2)

ppm = part per million,

lets so,

wt of rat hairs = 40*1.5*10^-4 g = 40*1.5*10^-4*10^-3= 0.000006 kg

content of rat hairs = 0.000006/1*10^-6 ppm = 6*10^-12 ppm

3)

0.28 ppm = 0.000279681 g/L

mol. wt of lead = 207.2

so moles of lead in 1 L = 0.000279681/207.2 = 0.00000134981 moles

molar conc. of lead = moles/litre =0.00000134981 moles/L = 1.35*10^-6 moles/L = 1.35*10^-6 M

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