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Postby gabbymaraziti » Sat Oct 12, 2019 10:22 pm

F.3 a) Write the formula for nitric acid. b) Without doing a calculation, estimate which element in nitric acid occurs with the greatest mass percentage.

Are we expected to be able to derive the formula for nitric acid and other compounds on our own?

Maria Poblete 2C
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Re: F.3

Postby Maria Poblete 2C » Sat Oct 12, 2019 10:51 pm

I was also wondering the same thing. I have an easier time deriving formulas for telltale compounds (ex. dihydrogen monoxide, haha) but am not sure if I should remember the methods of deriving for acids or oxides.

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Re: F.3

Postby preyasikumar_2L » Sat Oct 12, 2019 11:04 pm

a) I think this is supposed to be something that we have memorized, perhaps from the polyatomic ions (nitrate = NO3-). I know for me in AP Chem we had to memorize strong acids and bases and polyatomic ions, but I'm sure it wouldn't matter if you looked up the formula --> Nitric acid = HNO3

b) For this I think we should be able to derive this from prior knowledge and estimating, like H is about 1 g/mol, N is about 14 g/mol, and O is about 16 g/mol, and since there are 3 O it occurs in the greatest mass percentage.

Leyna Dang 2H
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Re: F.3

Postby Leyna Dang 2H » Sat Oct 12, 2019 11:12 pm

I'm not sure if we are expected to derive the formulas on our own, but hopefully this helps:

For part a, it helps to know that acids contain hydrogen and usually begin with an H. So, that gives you the first element of nitric acid. For the rest of the formula, I had to work backward. When you are usually given an ion and it ends in -ate, you change the -ate into a -ic when naming an acid. I applied this when writing the formula for nitric acid. I don't know if this is the right way of going around this but I basically assumed that because nitric ended in -ic, the ion it was before was probably NO3-, or nitrate. So, you end up with HNO3-.

For part b, you just look at the formula you got from part a and because the compound is composed of more than one oxygen (unlike hydrogen and nitrogen), we could assume that oxygen would have the greatest mass percentage.

Jasmine 2C
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Re: F.3

Postby Jasmine 2C » Sun Oct 13, 2019 10:55 am

I had the same worry as you. I saw so much practice problems asking us to name compounds and such, and with my super weak high school chem background, I immediately went to Fundamental Section D to read all about nomenclature. It provides very good explanations on how to name simple compounds, like nitric acid.

Nicholas Chin 4E
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Re: F.3

Postby Nicholas Chin 4E » Sun Oct 13, 2019 11:29 am

When I asked my TA they said that we are expected to memorize the names of cations and anions, but I'm not sure if we have to memorize the acids yet since that's something we will cover later.

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