What is the formula of aluminm hydroxide? (multiple choices listed in detail portion)?

Question

a) AlOH
b)Al (OH) 2
c) Al (OH) 3
d) Al3OH

Answer 1

C, Al(OH)3...
Would you like an explanation? Okay, I'm supposed to be learning about this in Chemistry right now, so, I think this is how it works...

If you study the periodic table of elements, then you will find the number of valence (or outer) electrons each element has. Al has 3, O has 6, and H has 1. Before we start, it is important to know that a filled orbital has 8 valence electrons... okay?
O and H combine, so they have a total of 7 valence electrons. You can imagine this by thinking of the letters OH surrounded by 7 dots in a circle, 2 pairs of dots on each side and 1 alone (a filled orbital with have four pairs opposite each other). The lone pair needs an electron, so it can borrow one from aluminum, which has 3 electrons. Aluminum loses its electron, so now it has 2, and the OH is now full, because it has 8 electrons. However, the aluminum has to get rid of its other two electrons, so another OH is brought in. The aluminum gives up an electron and the second OH is now full. Finally, the last OH pair is brought in and the aluminum gives away its last electron. So now, it is empty and the OH's are full. I guess they're balanced. Anyway, you are now left with 1 Al and 3 OH's, making Al(OH)3. Do you understand now?

Al (3), and OH (7) (because O=6 & H=1, which equals 7)...
Al - 1 = (2), so now OH = (8) (now it's full)
Al - 1 = (1), so a 2nd OH (7) is brought in, making it OH (8)
Al - 1 = (0), so a 3rd OH (7) is brought in, making it OH (8)

It took 1 Al and 3 OH's, so the new compound is Al(OH)3
Hope this helps!!!
P.S. sorry for any confusion earlier when I tried to "draw" them. The computer changed the spacing so all you could see was a mess of stars and stuff. : )

Answer 2

The answer is C. Here is a brief explanation on how you can attempt such kinds of questions in the future.

First of all, you'll have to find the oxidation numbers of the ions involved here: aluminum ion and hydroxide ion. You can find this from a standard table for oxidation numbers. For a test, since the teacher won't allow you to bring the table in with you, you'll have to memorize it yourself. I know it sucks, but that is the only way... Anyways, from that table you find out that Al has an oxidation number of 3+ and OH has an oxidation number of 1-.

Then, what you do is, make the oxidation number of Al the subscript (that is written below it) of OH and the oxidation number of OH the subscript of Al. Then, you get Al(OH)3

Hope this helps

Answer 3

c. Aluminum is a +3 cation, OH is a -1 anion.

Answer 4

c

Answer 5

C

Answer 6

C