Just to make this clear up-front: Moderators seldom close questions unilateral.
We've been more active recently due to overflowing queues, but we usually only close very clear cases. Most other decisions are made by community moderation, which is a democratic process. So please, if you find a closed question, unless you absolutely know it was close unilaterally by a moderator, do not assume it was.
In most cases, the moderators will err on the side of leaving a question open.
The rules have been written down and there is hardly any disconnect between how they are applied and how they are written down. Homework has and will probably always be a controversial subject within our user base, and if we were not to follow our own rules we could as well just close down ship.
[...] they do not seem to meet the criteria for "off-topic" at https://chemistry.stackexchange.com/help/on-topic .
I disagree. The page you cite is only the landing page. The very, very brief summary under which we actually consider questions. I am quite certain you are referring to this bullet point:
Do-my-homework questions: Homework questions are OK, but they must follow these guidelines. Please don't ask "do my homework for me" type questions – we only clear conceptual doubts in homework questions and will not do your work for you.
At a brief glance you might appear right.
I must admit the instructions could be clearer, because this section is linking to the homework policy. This is a discussion for another time, but maybe the section should read something like this:
Do-my-homework questions: Homework questions are OK, but they must follow the guidelines outlined in this meta post. Please don't ask "do my homework for me" type questions – we only clear conceptual doubts in homework questions and will not do your work for you.
(I would even cut the last sentence.)
In the comments you say:
What I'm saying is that the written rules don't say anything at all about this, they say only that you should show your work (if applicable) and ask about the concept you're confused by.
That actually makes me question whether or not you have yourself clicked through to the actual policy.
We quite recently noticed that there was a change in the UI. We have unfortunately not gotten around to fix this. We are all volunteers here after all. In any case, the OP of the closed question (and anyone who has the open/close privilege) will see a more detailed description of why this question was closed.
The linked policy has been around long before I started here. Throughout the years it was changed, little by little, there have been multiple discussions about how to change it and to make it clearer. One of those is quite recent. With some other points we got stuck due to not reaching consensus or even compromise.
The topic is difficult, especially since there is that dreadful effort criterion, which everybody has a very subjective opinion about.
Let's just look at the questions individually and try to keep an open mind about that effort criterion.
Is this a homework question? Possibly. Do I care? No, not a bit. Should it have been closed with the homework close reason? Maybe.
In my opinion, a question about a buffer, which does not at least in passing mention the Henderson-Hasselbalch equation constitutes a case of not enough effort. If altavista were still around I'm pretty sure it would have pointed to that equation. So this is the reason why I think it can be closed with the homework close reason.
On the other hand, I think this question is way too basic to fit our scope. Any textbook about general chemistry will have a better explanation of this concept. There are open books on the internet that explain this very well (and a couple of ones which are garbage). Chemistry.se is not supposed to substitute a textbook. So my personal choice would - in this case - have been to close it as a duplicate of Resources for learning chemistry; which would have been somewhat against our written rules. (Because we have not yet been able to find a compromise on that.)
In any case, this was rightfully closed according to the written rules.
I must admit I don't understand the close-voters either. Sure, this is a question mixing basic concepts of chemistry, but I cannot see why this would constitute closure according to the homework policy. I guess that is somewhat due to the fuzzy interpretation of that policy.
However, I must also admit, I don't feel strong enough about unilaterally reopening the question. That should also be a community decission.
[Please don't use edit statements, there is a history of the post for that.]
Travel back in time to see the version of the post when it was closed: revision 3. I must admit, I don't understand what the actual question is here:
Is this how moles work (can different substances be added like this)?
Now the question has been reformatted and reopened and gotten an answer.
At first glance this looked like one of the 'Am I right?' category. How to handle these has also been discussed: Policy on AMIRITE questions. It's not as clear, which is also a shortcoming of the homework policy.
However, I agree that the question should be open.
There are coming in plenty of questions every week. Many of them are of mediocre or worse quality. We are all volunteers and those who dig through the review queues watch out for protecting the quality of this site. We owe them thanks. I recently went through about 100 questions of this queue and it can be quite enraging. It's almost always a community decision and sometimes the community doesn't get it right. We are human, it happens. There are multiple ways for inquiry. They need to be used. If you don't know how, and you don't care to find out, then that shall no longer be our problem. There is plenty of help, and many people are willing to help. If the OP doesn't interact with the people s{..}he wants to answer the question, then this is also no longer our problem.
Your complaint that we follow invisible rules is not true.
The whole thing with the false premise. That has been just another issue and it has been discussed: I'm voting to close this question as off-topic because it's based on false premise. I don't think I need to repeat myself or others here.
I think people underestimate the degree to which it is aggravating to new users when there is a disconnect between the written rules and the actual rules. You read the rules page, you read all the sub-rules pages linked from the rules page, you verify that your question is compliant with the rules, you spend time crafting your question, only to get a notification that the question was removed anyway with no explanation given.
Well, this is not really true. Questions can't be closed without reason, and the asker will know that reason. I'm not sure how much any of these users have read the rules and make sure to comply with them; I'm also not quite sure how much time went into crafting the question. But that is certainly not the issue here. Those questions are not as bad as some others we get on a daily basis.
It might be aggravating to new users that there question is being closed, I actually sympathise with that. It is very well how they handle what comes after. You are looking for help, then please do your part. Others are volunteering their free time here, and even if they decide to pot a question on hold, they have at least read it.