Figuring out formula from looking at name

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In summary, there is no way to know that aluminum sulfate has the formula of Al2(SO4)3 just by looking at the name "Aluminum Sulfate". However, if you memorize the periodic table, you will know that Al is Aluminum and SO4 is Sulfate. Additionally, you can look up the charges for each molecule on a list somewhere.
  • #1
leroyjenkens
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For example, is there any way to know that aluminum sulfate has the formula of Al2(SO4)3 just by looking at the name "Aluminum Sulfate"? It seems like while doing chemistry problems, the problems kind of assume you can do that.

Thanks.
 
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  • #2
Well, aluminium ions are Al3+ and sulfate is (SO4)2-. So the only way to combine them and get something neutral back, is in the ratio 2 : 3.
 
  • #3
Right, so Al2 makes it now a +6 charge and (SO4)3 will have a -6 charge. But you do in fact need to remember Al is Aluminum and SO4 is Sulfate. But as far as the charges, we were always allowed to look at the periodic table for those. We had a whole week where we just memorized different things like carbon dioxide, water, methane, ethane, oxalate, sulfate, sulfite, etc. If you weren't required to do so I would suggest doing it anyways, it makes chem WAY easier.
 
  • #4
Thanks for the responses guys.
We had a whole week where we just memorized different things like carbon dioxide, water, methane, ethane, oxalate, sulfate, sulfite, etc. If you weren't required to do so I would suggest doing it anyways, it makes chem WAY easier.
Is there like a list of all of them somewhere for me to study? What are they called? I'll go look it up.
I do need to learn that stuff, because when I see "sulfate" all I know is it's sulfur.
 
  • #5


I didn't actually watch this video lol, but I am sure it will be helpful. If not, basically everything you need to remember is on the board behind him. Except I don't think methane was on his list, which is CH4. If you need any more help just ask.
 
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  • #6
Awesome, thanks. This forum is making me more and more un-retarded every day.
 
  • #7
Yeah no lie, I'm going to ask so many math questions when i get to precalc (I suck at math) although this college algebra stuff is easy so far.
 
  • #8
I wrote all of those down, but I noticed they're all charged molecules. Is there a reason for that? You mentioned methane isn't on the list, and since it's not charged, maybe that's why.
 
  • #9
leroyjenkens said:
charged molecules

They are called ions :wink:

--
 
  • #10
Yes they are but remember a lot of times you have to combine them with ions and anions and balance them out. Also what borek says is correct but I believe many of them have negative charges too (anions).
 
  • #11
Entropee said:
Also what borek says is correct but I believe many of them have negative charges too (anions).

Just to clear things up... Ions with a positive charge are called cations and ions with a negative charge are called anions (As you rightly said).

:)
 
  • #12
Ah yes forgive me, I forgot they were called cations, been a while now.
 

Related to Figuring out formula from looking at name

1. How do I determine the formula of a compound from its name?

There are a few steps you can follow to figure out the formula of a compound from its name. First, identify the elements present in the compound. Then, determine the charge of each element based on its position on the periodic table. Next, use the charges to balance the overall charge of the compound. Finally, write the elements and their subscripts to form the formula.

2. What is the difference between empirical and molecular formulas?

Empirical formulas show the simplest whole-number ratio of atoms in a compound, while molecular formulas show the actual number of each type of atom in a molecule. Empirical formulas are often used for compounds with unknown molecular formulas, while molecular formulas are used for compounds with known molecular structures.

3. Can I determine the formula of a compound just by looking at its name?

Not necessarily. While the name of a compound can give you clues about its composition, it may not always be enough to determine the exact formula. It's important to also consider the charges of the elements and their ratios when figuring out the formula of a compound.

4. How do I know if a compound is ionic or covalent based on its name?

Compounds with "ide" endings, such as sodium chloride, are usually ionic, while compounds with "ate" or "ite" endings, such as sulfuric acid or sulfurous acid, are usually covalent. However, there are exceptions to this rule, so it's important to also consider the composition and charges of the elements in the compound.

5. What is the significance of parentheses in chemical formulas?

Parentheses in chemical formulas indicate that the elements within them are bonded together as a group. This means that the subscript outside of the parentheses applies to all elements within the parentheses. This is often used to show multiple copies of a polyatomic ion in a compound.

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