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Answer 1 · 2015-06-27T11:55:08

That much sodium nitrate contains $1.4 * 10^(22)$ formula units.

Since sodium nitrate is an ionic compound, you can't really say that you're dealing with molecules, but with formula units.

In order to calculate how many formula units a certain mass of a substance contains, you need to do two things

determine how many moles are present in that many grams by using the substance's molar mass;
determine how many formula units you have in that many moles by using Avogadro's number.

So, use sodium nitrate's molar mass to determine how many moles are present in 2 g

$2cancel("g") * "1 mole "/(85.0cancel("g")) = "0.0253 moles"$

Avogadro's number tells you that 1 mole of any substance contains exactly $6.022 * 10^(23)$ molecules of that substance.

![https://shirleycahyadi.wordpress.com/2013/09/30/different-formulas-for-quantitative-chemistry-and-mole-conversion/](useruploads.socratic.org)

This means that you have

$0.02353cancel("moles") * (6.022 * 10^(23)"f. units")/(1cancel("mole")) = color(green)(1.4 * 10^(22)"f. units"$