Formula Units

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Formula Units

Postby anjali41 » Wed Oct 02, 2019 2:16 pm

I was just wondering what formula units are. I think I saw them come up in the textbook and never learned about them in high school chem. Can someone explain what they are and their relevance?

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Re: Formula Units

Postby 205296774 » Wed Oct 02, 2019 2:22 pm

Sure! Formula units are just a type of particle associated with ionic compounds so you only use the term formula units when the problem relates to an ionic compound. Other "particles" are atoms and molecules but those are associated with elements and molecular compounds, respectively. Basically, formula units are just a type of particle like atoms or molecules.

Hope this helps!

Lauren Haight 1E
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Re: Formula Units

Postby Lauren Haight 1E » Wed Oct 02, 2019 2:23 pm

According to the textbook glossary, formula units are the group of ions that matches the formula of the smallest unit of an ionic compound. In terms of an example, the book provides the following: the formula units for sodium chloride, or NaCl, are the one cation of Na+ and the one of anion Cl-. So essentially, I would say that formula units are the anions and cations that make up an ionic compound.

Jessica Booth 2F
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Re: Formula Units

Postby Jessica Booth 2F » Wed Oct 02, 2019 10:03 pm

Formula units can be thought of as the same thing as number of molecules. So when given a problem that asks to find the formula units of a compound you just take the number of moles and multiply by Avogadro's number (6.022 x 10^23).

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Re: Formula Units

Postby KaitlynBali_4B » Thu Oct 03, 2019 2:28 am

Making this connection helped me with one of the homework problems: 6.022*10^23 formula units = 1 mol of an ionic compound

Naji Sarsam 1F
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Re: Formula Units

Postby Naji Sarsam 1F » Thu Oct 03, 2019 8:50 am

Formula units are different from molecules in that all atoms in an ionic compound have formed atomic bonds with other atoms, to form a lattice. In this way, ionic compounds are not groups of moleculas which are associeated with one another through intermolecular bonds. Rather, they are one coherent compound. Thus, since there is no way to define an individual molecule if all atoms are bonded together, chemists call the ratios of each atom to one another in the ionic compound the formla unit.

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Re: Formula Units

Postby PGao_1B » Thu Oct 03, 2019 9:22 am

Formula units are empirical formulas of any ionic or covalent network solid compound used as an independent entity for stoichiometric calculations. It is the lowest whole number ratio of ions represented in an ionic compound. There are (Avogadro's number) formula units in 1 mole of ionic compound.

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