Writing Empirical Formulas

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Aedra Li 3H
Posts: 40
Joined: Fri Aug 30, 2019 12:17 am

Writing Empirical Formulas

Postby Aedra Li 3H » Fri Oct 04, 2019 3:59 pm

Once you have determined how much of each compound is required for an empirical formula, how do you know what order to write the compounds in when you are rewriting whole empirical formula?

Alice Chang 2H
Posts: 101
Joined: Fri Aug 30, 2019 12:18 am

Re: Writing Empirical Formulas

Postby Alice Chang 2H » Fri Oct 04, 2019 4:08 pm

TIL:

I just found this online, hope this helps!

There's something called Hill System. This is the system of writing chemical formulas. In this system the carbon atoms are first, then hydrogen atoms and then other in alphabetical order. When the formula contains no carbon or hydrogen atoms, then all the elements are sorted alphabetically.


You can find more info/where I found the answer here: https://chemistry.stackexchange.com/questions/1239/order-of-elements-in-a-formula

kpang_4H
Posts: 55
Joined: Fri Sep 20, 2019 12:17 am

Re: Writing Empirical Formulas

Postby kpang_4H » Fri Oct 04, 2019 6:24 pm

I noticed that in the practice problems, you can just write the elements in the same order the mass percentage compositions or mass of the elements are shown.

Ruth Glauber 1C
Posts: 100
Joined: Wed Sep 18, 2019 12:20 am

Re: Writing Empirical Formulas

Postby Ruth Glauber 1C » Sat Oct 05, 2019 5:38 pm

I believe you tend to put Carbon, Hydrogen and Oxygen first, and go off of the others in alphabetical order?

Rodrigo2J
Posts: 102
Joined: Sat Jul 20, 2019 12:16 am

Re: Writing Empirical Formulas

Postby Rodrigo2J » Sat Oct 05, 2019 6:46 pm

I actually asked the TA this question and he said that the order of the elements doesn't necessarily matter as long as you have the correct subscripts and ratios for each atom. But just for a reference, if it is an ionic substance start with the metal and then the nonmetal(s), if it is an organic compound usually start with carbon then hydrogen, oxygen, and so on.

405398682
Posts: 26
Joined: Wed Sep 18, 2019 12:21 am

Re: Writing Empirical Formulas

Postby 405398682 » Sat Oct 05, 2019 11:17 pm

The order of the elements is not that important in this kind of question. As long as you get the ratio of the mass of every element correct, I think you will be fine.

AveryAgosto
Posts: 76
Joined: Wed Sep 18, 2019 12:16 am

Re: Writing Empirical Formulas

Postby AveryAgosto » Sun Oct 06, 2019 11:05 pm

I think for the material we are learning in 14A, the order is not important. I think the ratio's are the important part.

Grecia Velasco 4D
Posts: 56
Joined: Thu Jul 11, 2019 12:17 am

Re: Writing Empirical Formulas

Postby Grecia Velasco 4D » Wed Oct 09, 2019 12:25 pm

Write the elements in the same order that the mass % composition is in. For example: H 25%, O 25%, C 25%, Fe 25% = HOCFe when solving for empirical formula.

EvanWang
Posts: 101
Joined: Sat Sep 07, 2019 12:16 am

Re: Writing Empirical Formulas

Postby EvanWang » Wed Oct 09, 2019 12:49 pm

Generally, the order the elements are given in the problem will be the same order you can write them in your answer. In organic molecules, that normally means C, H, then everything else.


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