Question #1e5b3

1 Answer
Jul 1, 2017

Answer:

#2.4 * 10^(24)#

Explanation:

The first thing that you need to do here is to convert the mass of water to moles by using the compound's molar mass.

#36 color(red)(cancel(color(black)("g"))) * ("1 mole H"_2"O")/(18.015color(red)(cancel(color(black)("g")))) = "1.998 moles H"_2"O"#

Now, you know that very mole of water contains

  • two moles of hydrogen, #2 xx "H"#
  • one mole of oxygen, #1 xx "O"#

This means that your sample contains

#1.998 color(red)(cancel(color(black)("moles H"_2"O"))) * "2 moles O"/(1color(red)(cancel(color(black)("mole H"_2"O")))) = "3.996 moles O"#

Finally, to find the number of atoms of oxygen present in the sample, use the fact that #1# mole of elemental oxygen must contain #6.022 * 10^(23)# atoms of oxygen #-># this is the definition of a mole given by Avogadro's number.

You will end up with

#3.996 color(red)(cancel(color(black)("moles O"))) * (6.022 * 10^(23)color(white)(.)"atoms O")/(1color(red)(cancel(color(black)("mole O")))) = color(darkgreen)(ul(color(black)(2.4 * 10^(24)color(white)(.)"atoms O")))#

The answer is rounded to two sig figs.