Question

A 2.578 g of leaf sample was dried. The dried material weighting 0.7692 g was ashed and dissolved in a 500 mL. The concentration of a metal in the final solution was reported as 1.75 mg/L. Report the concentration as ppm of the metal in
a) the wet sample,
b) the dry sample,
c) find % of water in the original sample.

Answer 1

80627 Chemistry, Other

A 2.578 g of leaf sample was dried. The dried material weighting 0.7692 g was ashed and dissolved in a 500 mL. The concentration of a metal in the final solution was reported as 1.75 mg/L. Report the concentration as ppm of the metal in:

a) the wet sample

b) the dry sample

c) find % of water in the original sample.

Answer:

The amount of metal in the whole sample:

m (Me) = 1.75 X 0.5 = 0.875 mg

a) Concentration of metal in the wet sample is: 0.875 mg / 0.002578 kg = 339 ppm

b) Concentration of metal in the dry sample is: 0.875 mg / 0.0007692 kg = 1 137 ppm

c) m (H₂O) = 2.578 - 0.7692 = 1.8088 g

% (H₂O) = 1.8088/2.578 X 100 = 70%

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