These two questions are not duplicates

Question

The two questions are:

Why is arsenous acid denoted H3AsO3?

and

Why is methane's molecular formula conventionally "CH₄", while water is "H₂O" (among others)?

The second question was recently closed as a duplicate of the first. I agree that the answer to the first question does contain a viable answer to the second question. However, the answer to the second question is related, but not relevant, to the first question.

I have two specific concerns about closing the second question and marking it as a duplicate of the first.

1. Individuals who are confused about the notation issue in the second question (mostly individuals who are beginning their studies or who have little to no chemistry background) will not understand the connection between the the two questions, as the first question appears to be about acids and the second does not appear to be about acids (even though it really is). An individual who understands the link between the two questions, likely already knows the answer to both.

2. The best answer to the first question includes a valid answer to the second question, but the best answer to the second question is not relevant to the first question. A good answer to a question about rectangles will out of necessity be applicable to squares, but a good answer about squares may not be relevant to rectangles. Similarly, an answer about the notation of all compounds will be applicable to a subset of compounds, but an answer restricted to that subset will not necessarily be applicable to the whole.

Answer 1

However, the answer to the second question is related, but not relevant, to the first question.

&

Similarly, an answer about the notation of all compounds will be applicable to a subset of compounds, but an answer restricted to that subset will not necessarily be applicable to the whole.

Remember that closing as duplicate is one-way. It basically means "Look for an answer to this question over there". I've seen it used on SO (though that's not always a good indicator of policy) to connect questions with completely different scenarios with nearly the same issue.

Individuals who are confused about the notation issue in the second question (mostly individuals who are beginning their studies or who have little to no chemistry background) will not understand the connection betweis more en the the two questions, as the first question appears to be about acids and the second does not appear to be about acids (even though it really is).

Scrolling down to the answers ought to solve the confusion. If the individual is interested in looking for an answer to the question, I doubt they'll just glance at the acid question and turn away. Besides, the answer on the CH4 question is still visible.

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MSO seems to disagree with me. Sort of:

This post says

Rule of thumb: If you ask a question similar to another question and it is likely to get the exact same answer, you have yourself a duplicate question.

Of course, here it talks of exact same answer, though I think that a deeper answer is OK.

This post has some conflicting answers. Jalf seems to be against linking to overarching "duplicate answers", but the motivation there is about linking to a long answer that deals with many other issues. I'm not sure how the arsenous post can be classified. Sbi seems to be fine with closing such things as dupes, as long as the closed question isn't deleted. GN's answer seems to also be against closing such "dupes", bit I'm not sure.

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I myself am not too sure of my decision here, and I'm open to reopening it (and maybe adding a "related" hatnote). So we'll see what the community feels and act accordingly :)

Answer 2

How many questions do we want in the category "why are atoms listed in this particular order for this empirical / molecular formula?"

I'd suggest that we want exactly one.

That is rather the point of StackExchanges - to give definitive answers to questions.

This answer: https://chemistry.stackexchange.com/a/538/25 is a definitive answer to that question.

All others should be closed as duplicates.

If necessary, the question associated with that answer - Why is arsenous acid denoted H3AsO3? - (and in particular its title) could be edited to show that that is the definitive question.

Then, all other questions that are duplicates or subsets of "why are atoms listed in this particular order for this empirical / molecular formula?" should be closed as duplicates of that definitive question.