A given sample of caffeine, C8H10N4O2, has 6.47 x 1022

atoms of carbon. How many atoms of hydrogen in the same

sample?

8.08 × atoms of hydrogen

Explanation:

From the given data, we have two categories of variables (unknowns):

The longer route would be to solve for these variables first, by determining the number of moles of the Caffeine sample (0.134 moles of C8H10N4O2) from the mass of carbon (12.89 g = 1.07 moles in 6.47 atoms) provided. And then solve for the number of atoms of H. [N.B: 1 mole of ANY substance = 6.022 × atoms ]

Alternatively and quicker, we can use the mole ratios of the Carbon:Hydrogen atoms in the compound.

8 : 10 ≡ 4 : 5

If   4 moles -- 6.47 atoms

Then 5 moles -- ?? atoms

⇒ No. of atoms of Hydrogen =

=8.08 × atoms of hydrogen

not clear