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When the textbook asks for amounts of compound in units of formula units, what units are they expecting the answer to be in? Also, when would formula units be used over other units of measurement in real life applications?
A formula unit is a group of ions. You can think of it as a "molecule" of an ionic compound such as NaCl (table salt). When the textbook asks for the amount of a compound in formula units it is asking for a count of formula units or "How many formula units are there in this sample." Depending on the quantity being referred to, you could express this in moles (ex. 3 mol NaCl) or in individual formula units (ex. 50 NaCl). Formula units tell you a count, not a mass, which could be useful in real life applications like determining quantities for a chemical reaction.
In the book, its specifying formula units just as a generic unit. For example, in middle school or earlier math classes, if units were not specified, you would just put "units." Similarly, formula units could me molecules, atoms, etc., but for the purpose of these exercises, the unit is just "formula units." ex) 1 mol= 6.022 x 10^-23 formula units
When a question asks you to find the number of formula units, you use avogadro's number and solve the problem the same way you would if it had asked for the number of atoms, so are formula units and atoms basically the same?
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