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### F.13 homework problem

Posted: Thu Oct 03, 2019 12:57 am
In F.13, we are asked to find the empirical formula of a phosphorus and chlorine compound. We get PCl5 but part b asks for the specific name of this compound. Is this something we memorize or supposed to know already? If someone could answer this and try to explain how we name compounds that would be amazing :)

### Re: F.13 homework problem

Posted: Thu Oct 03, 2019 1:02 am
I was also not sure about that. I looked up the name of the compound.

### Re: F.13 homework problem

Posted: Thu Oct 03, 2019 11:14 am
I don't think naming compounds is something we will be tested on or actually have to know. However, you should be expected to remember the formulas of common compounds such as hydrochloric acid and calcium carbonate.

In this case, PCL5 is a molecular compound, so the rule for this is replacing the ending of the second element Cl with "ide" and using the prefix "penta" to indicate the number of the element present. Thus, the name is phosphorus pentachloride.

### Re: F.13 homework problem

Posted: Thu Oct 03, 2019 1:19 pm
Since phosphorus and chlorine are covalently bonded together, they make a covalent compound. Simple covalent compounds are generally named by using prefixes to indicate how many atoms of each element are shown in the formula. Also, the ending of the last (most negative) element is changed to -ide. The prefixes used are mono-, di-, tri-, tetra-, penta-, hexa-, and so forth

### Re: F.13 homework problem

Posted: Thu Oct 03, 2019 11:03 pm
I'm guessing covalent compounds will come up a lot in the class, so here are the first ten prefixes for the future. Just add the corresponding prefix for the number of atoms. 1=mono, 2=di, 3=tri, 4=tetra, 5=penta, 6=hexa, 7=hepta, 8=octa, 9=nona, 10=deca.