Two such questions -
I would argue in most cases these sort of questions which ask a question are either homework or are too broad. Your first example I would say could be homework because it doesn't show any effort to solve the problem, but it could also very easily be closed as too broad since it is asking for a list of chemicals that might perform a reaction.
The second question does seem to try to explain their reasoning, but their explanation is confusing. So I would lean more towards unclear what they are asking.
Without looking at the two specific examples, I am just going to answer the question in the title. The answer is:
This cannot be taken as a general rule.
Each question should really be judged on its own. If we applied your rule to every question here, we would lose a lot of interesting content.
Anybody who has >3k rep may use their close vote as they wish. However I would like to repeat my plea: if you think that a question can give rise to an interesting answer from which we can all learn from, please consider giving it a chance.
Again I would like to emphasise that I am not talking about the two examples specifically - I am just speaking in general terms.
It’s no secret that I dislike the homework close reason. For that reason I really do not want to discuss this further. However, I thought it was necessary to refute such a blanket statement.
As a final note to anybody who reads this, please stop flagging homework posts for moderator attention. If you have been doing this, your flags will have been declined, and will continue to be declined.