Question #c8c79

1 Answer
Oct 12, 2015


#15 * 20^(23)"atoms"#


The first thing you need to determine is how many atoms you get per molecule of hydrogen sulfide, #"H"_2"S"#.

You know by looking at the subscripts in the chemical formula that one molecule of hydrogen sulfide contains

  • two atoms of hydrogen
  • one atom of sulfur

So one molecule contains a total of three atoms.

Next, find you how many molecules of hydrogen sulfide you get in that many moles. You know that one mole of a substance contains exactly #6.022 * 10^(23)# molecules of that substance - this is known as Avogadro's number.

In your case, you will have

#0.8color(red)(cancel(color(black)("moles H"_2"S"))) * (6.022 * 10^(23)"molecules")/(1color(red)(cancel(color(black)("mole H"_2"S")))) = 4.818 * 10^(23)"molecules"#

This means that the number of atoms will be

#4.818 * 10^(23)color(red)(cancel(color(black)("molecules H"_2"S"))) * "3 atoms"/(1color(red)(cancel(color(black)("molecule H"_2"S")))) = 15.45 * 10^(23)"atoms"#

I'll leave the answer rounded to two sig figs, despite the fact that you only gave one sig fig for the number of moles of hydrogen sulfide

#"no. of atoms" = color(green)(15 * 10^(23))#