Formula Units

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Angelica Mercado 1A
Posts: 21
Joined: Fri Sep 29, 2017 7:04 am

Formula Units

Postby Angelica Mercado 1A » Thu Oct 05, 2017 10:36 pm

What is a formula unit? Does this by default always indicate the same thing, or does the definition change depending on the context of the problem?

Joyce Lee 1C
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Re: Formula Units

Postby Joyce Lee 1C » Thu Oct 05, 2017 10:40 pm

A formula unit is a group of ions. Formula units are different for each ionic compound. For example, the formula unit of (NH4)2SO4 consists of two NH4^+ ions and one SO4^2- ion. But, NaCl consists of one Na^+ ion and one Cl^- ion.
1 mole = 6.022 x 10^23 formula units.

I hope this cleared it up a bit!

Rachel Formaker 1E
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Re: Formula Units

Postby Rachel Formaker 1E » Thu Oct 05, 2017 10:50 pm

Discussing the formula unit of an ionic compound is equivalent to discussing a molecule of a covalently bonded compounds.
It is technically incorrect to call a unit of NaCl a molecule, although that may be what you have heard in past chemistry classes. Call it a formula unit instead.

Fundamentals Section C discusses this more thoroughly.

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