The concentration of the alkane c20h42 (fm 282.56) in a particular sample of rainwater is 0.2 ppb. assume that the density of rainwater is close to 1.00 g/ml and find the molar concentration of c20h42.

Formula used for determining the molarity is:

 -(1)

Number of moles of solute that is is determined as:

 -(2)

Mass of the solute can be calculated as:

- (3)

density of rain water = 1.00 g/mL (given)

Concentration of = 0.2 ppb (given)

Since,

So, 0.2 ppb =

Substituting the values in formula (3):

Mass =      (As 1 mg = g).

Now, substituting the values of mass and formula mass in formula (2):

Number of moles =

Volume of solution = 1 L

Substituting the values of number of moles and volume of solution in formula (1):

Molarity =

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