Mole ConceptHard
Question
The mercury content of a stream was believed to be above the minimum considered safe limit (1 part per billion, by mass). An analysis indicated that the concentration was 1.68 parts per billion. How many Hg atoms are present in 15 L of water, the density of which is 0.998 g/ ml. (Hg = 200)
Options
A.7.57 × 1013
B.7.57 × 1019
C.7.57 × 1016
D.5.37 × 1016
Solution
Mass of mercury present = $\frac{1.68}{10^{9}}$× (15000 × 0.998) = 2.515 × 10−5 g
Number of Hg-atoms = $\frac{2.515 \times 10^{- 5}}{200} \times 6 \times 10^{23} = 7.545 \times 10^{16}$
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