A sample of the male sex hormone testosterone,C19H28O2, contains 3.88 * 10^21 hydrogen atoms.

(a) How many atoms of carbon does it contain?

(b) How many molecules of testosterone does it contain?

(c) How many moles of testosterone does it contain?

(d) What is the mass of this sample in grams?

Answer:

To find atoms of carbon, we take the number of hydrogen atoms and multiply the number by 19/28 (ratio of carbon to hydrogen atoms), thus cancelling the number of hydrogen atoms and getting carbon atoms.

To find, the number of molecules we use the ration of 1/28, where 1 molecules of C19H28O2 has 28 H atoms.

To find the moles of testosterone, we have to use Avogadro's number 6.022 molecules/mol to cancel the number of molecules from part b and get the number of moles.

To find the mass, we have to use the molar mass of C19H28O2, 288.42g/mol so we can cancel the number of moles from part c and get the number of grams.

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