Question #07ab7

1 Answer
Stefan V.
Oct 12, 2017

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.

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