## Formula unit

Lorena Zhang 4E
Posts: 63
Joined: Fri Sep 28, 2018 12:16 am

### Formula unit

There are several practice problems that ask for the formula unit of a molecule or ion. I am not sure what that means.

rosemarywang4i
Posts: 34
Joined: Fri Sep 28, 2018 12:28 am

### Re: Formula unit

I'm pretty sure that 'formula unit' is another term for the empirical formula. But perhaps if you link some of the practice problems we can get a better idea of what you're confused about.

Lorena Zhang 4E
Posts: 63
Joined: Fri Sep 28, 2018 12:16 am

### Re: Formula unit

For example, E 25 asks for the number of KNO3 formula units in 0.750 mol KNO3.

Sam Kelly 1K
Posts: 30
Joined: Fri Sep 28, 2018 12:16 am

### Re: Formula unit

Yeah as Rosemary said, formula unit refers to the empirical formula of a compound, or the lowest ratio of ions in an ionic compound. For example, NaCl is the formula unit of table salt/sodium chloride. Other compounds like NH4NO2 are a little more complicated, since one might think it could just be simplified down to NH2O. Since we need to show the different ions, however, the notation must remain as is.