Question #07ab7

1 Answer
Oct 12, 2017

Answer:

#5.8 * 10^(21)#

Explanation:

Your tool of choice here is Avogadro's constant, which acts as the definition of a mole.

In order to have #1# mole of sodium oxide, you need to have #6.022 * 10^(23)# formula units of sodium oxide #-># this is known as Avogadro's constant.

#color(blue)(ul(color(black)("1 mole Na"_2"O" = 6.022 * 10^(23)color(white)(.)"formula units Na"_2"O")))#

So if you know for a fact that #1# mole of sodium oxide contains #6.022 * 10^(23)# formula units of sodium oxide, you can say that your sample will contain

#9.7 * 10^(-3)color(red)(cancel(color(black)("moles Na"_2"O"))) * (6.022 * 10^(23)color(white)(.)"formula units Na"_2"O")/(1color(red)(cancel(color(black)("mole Na"_2"O"))))#

# = color(darkgreen)(ul(color(black)(5.8 * 10^(21)color(white)(.)"formula units Na"_2"O")))#

The answer is rounded to two sig figs, the number of sig figs you have for the number of moles present in the sample.