Question F3(6th Edition)

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Danny Zhang 4L
Posts: 62
Joined: Fri Sep 28, 2018 12:26 am

Question F3(6th Edition)

Postby Danny Zhang 4L » Tue Oct 02, 2018 10:02 pm

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

I am only using this problem as an example. When the question asks for the formula of a certain compound, are we supposed to figure it out ourselves or are we supposed to look it up? If it is the first case, I would like to know how you would figure out the formula of nitric acid.

Kate Chow 4H
Posts: 61
Joined: Fri Sep 28, 2018 12:28 am

Re: Question F3(6th Edition)

Postby Kate Chow 4H » Tue Oct 02, 2018 10:07 pm

Based on what Dr. Lavelle said in class, for now it's fine if we look up the formulas of compounds. Eventually, we'll have to memorize some of the more common compounds, but he'll teach us and also let us know when.

Mindy Kim 4C
Posts: 65
Joined: Fri Sep 28, 2018 12:25 am

Re: Question F3(6th Edition)

Postby Mindy Kim 4C » Tue Oct 02, 2018 10:10 pm

And in regards to naming acids, compounds with a suffix of -ate have the suffix of "-ic" and "acid." Compounds with a suffix of -ite have the suffix of "-ous" and "acid." Therefore, since the compound is nitric acid, the compound is nitrate, which is NO3-. Adding a hydrogen of +1 charge balances out the NO3-. Therefore, the compound is HNO3.

005115864
Posts: 64
Joined: Fri Sep 28, 2018 12:15 am

Re: Question F3(6th Edition)

Postby 005115864 » Tue Oct 02, 2018 10:12 pm

Hi,

Okay so this is a question that is testing your knowledge on polyatomic ions and acids which should've been a topic covered in your high school chemistry class. To start off, nitric acid has the word acid in it and knowing from general chemical rules, almost all acids begin with a hydrogen which is what makes them acidic. Not only that, they also tell you it is nitric acid. Note, nitRIC acid is different from nitROUS acid. The key difference between these polyatomic ions is Nitric acid is NO3^-1 where as Nitrous Acid is NO2^-1 both of which, though, are bonded to a hydrogen. This is what makes them acidic.

Additionally, to estimate the greatest mass percentage I would simply use what you already know to your advantage. For instance, we now know that Nitric acid is HNO3. So, using the periodic table or your memory, you know that the mass of H is 1.01 g/mol, N is 14.01g/mol and O is 16g/mol. Since Oxygen is the most present in the compound with the highest mass, it is safe to assume it will have the highest mass percentage without using math. It's just memorization but I hope this explanation was helpful.


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