Question #6a19b

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Answer 1 · 2017-07-18T02:19:07

$3.0 xx 10^23$ $"atoms"$

We're asked to find the number of atoms in $1.6$ $"g CH"_4$ .

To do this, we can first find the number of moles of $"CH"_4$ present, using the molar mass of methane ( $16.04$ $"g/mol"$ ):

$1.6cancel("g")((1color(white)(l)"mol CH"_4)/(16.04cancel("g CH"_4))) = 0.0997$ $"mol CH"_4$

Now, we can use Avogadro's number to find the number of molecules of $"CH"_4$ present:

$0.0997cancel("mol CH"_4)((6.022xx10^23color(white)(l)"molecules CH"_4)/(1cancel("mol CH"_4)))$

$= 6.01xx10^22$ $"molecules CH"_4$

Now, we ask ourselves, "How many atoms are in one molecule of methane?"

Well, there is $1$ $"C"$ and $4$ $"H"$ , which totals to $color(red)(5$ . We can use this relationship to find the number of atoms:

$6.01xx10^22cancel("molecules CH"_4)((5color(white)(l)"atoms")/(1cancel("molecule"))) = color(blue)(3.0xx10^23$ $color(blue)("atoms"$