Need help on the two problems below: 25. A bottle is labeled 56.2 ppm FeCl 3 . E

Question

Need help on the two problems below:

25.

A bottle is labeled 56.2 ppm FeCl3. Express this concentration in ppm Fe3+ and in molarity.

30.

What type of glassware should be used when making up solutions when you need to know concentrations accurately? Under what circumstances can graduated cylinders be used to prepare solutions?

A bottle is labeled 56.2 ppm FeCl3. Express this concentration in ppm Fe3+ and in molarity. 30. What type of glassware should be used when making up solutions when you need to know concentrations accurately? Under what circumstances can graduated cylinders be used to prepare solutions?

Explanation / Answer

given concentration of FeCl3 is 56.2 ppm

=> 56.2 g of FeCl3 is present in 1000000 g of water

molar mass of FeCl3 = 162.2

now mole of FeCl3 = 56.2/162.2 = 0.34648

FeCl3 ------> Fe+3 + 3Cl-

1 mole of FeCl3 gives 1 mole Fe+3 and 3 mole Cl-

hence mole of Fe+3 present = 0.34648

hence mass of Fe+3 = mole * molarmass of Fe = 0.34648 * 55.845 = 19.35 ppm

mole of Cl - = 0.34648*3 = 1.04

mass of Cl- = mole * molarmass of Cl = 1.04*35.5 = 36.92

hence concentration of Fe+3 = 19.35 ppm and Cl- = 36.92 ppm

30.

Graduated cylinders, beakers, volumetric pipets, burets and volumetric flasks are five kinds of glassware often used to measure out specific volumes. Volumetric pipets, flasks and burets are the most accurate; these are typically calibrated to a high level of accuracy

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