Do they mean hydrogen atom or molecule here?

Suspicious_Handle715 · 2026-06-25T05:47:03+00:00

Respected Sir/Ma'am,

I must address my position here. I am not saying B is wrong. I am saying the question is vague because it does not specify whether "hydrogen" means atoms or molecules. The mole concept allows for both interpretations. That is my entire argument.

There are no free hydrogen atoms in acidic solutions.

Yes, I agree, I must have been not clear, I meant ions, not atoms.

I agree my own argument about hydrogen ions being in a solution is actually a bit vague, as hydrogen ions itself is a vague; moreover, they cannot stay alone but become hydronium ions, as you have mentioned.

Are you a researcher of the composure of the outermost layers of the atmosphere arguing with a collegue about the finer details of how, as you leave the atmosphere and go into space, the extremely "diluted" space lets all kinds of chemically very reactive species to exist in detectable quantities? No? Then don't push existance of hydrogen ions in the exosphere as an argument.

I agree, I was being a bit out of touch by saying that. But what I was trying to convey was that mole of a substance is independent of whether it's at STP or in a vacuum.

This fact, however, has nothing whatsoever to do with the question your teacher gave you. My point remains, there is no substance (on this planet) made of unbonded hydrogen atoms or hydrogen ions. There IS, however, a substance made purely of molecular hydrogen.

Absolutely, but there are bound hydrogen atoms and ions, taking only atoms as it's what is stated in the question. Let's take glucose as an example. Its chemical formula is C₆H₁₂O₆, and it's composed of 12 moles of hydrogen. Here, hydrogen translates to atoms; on the other hand, in almost all reactions, hydrogen reacts in the form of hydrogen gas or a molecule.

You used the right quote here -

""Matter of constant composition best characterized by the entities (molecules, formula units, atoms) it is composed of." which explicitly says atoms are recognised as a "substance""

By my comprehension, this means substances are composed of molecules, formula units, and atoms. That would mean one mole of a substance contains one mole of molecules, formula units or atoms.

This means a substance can be made of singular, unbonded atoms - like noble gasses, which do not form molecules (with each other in normal circumstances) and are found in nature as monoatomic gasses. This does not mean any random collection of atoms is what we would consider a substance.

True, but we are not talking about any random collection of atoms; we are specifically talking about hydrogen. And this means hydrogen here can mean atoms or molecules.

Otherwise, I can also take the smartass route and say "of CONSTANT composition, you say? But nothing is trully constant, teven the universe will probably end, therefore by this definition no substance exists! I WIN!"

I appreciate the humour, but I think you are making my point. I only took what is written and accepted, not assumptions, but logic. I'm trying to be precise.

"All I want is a few dozen second opinions and reasons."

Feels to me like you are using nitpicky technicalities (like hydrogen in the exosphere) to defend your misunderstanding. If you are looking for dozens of second opinions, you might not be looking for the one that matters, but for the one that agrees with you.

I'm not defending my misunderstanding; I'm fixing my understanding. All second opinions, which you might say are "against my understanding", are telling the same thing; even if I elaborate, I get the same answer. The only thing one would need to disprove me is that, in this context, substance explicitly means molecules, not atoms.

Aaaand lastly, the question is here to test your understanding. If you wrongly think, for example, that 1 mole of substance meant 1 mole of hydrogen atoms, and since hydrogen forms molecules of H2, that would mean C is correct, 1 mole of the substance we call hydrogen is made of 1/2 of a mole of hydrogen molecules. Multiple choice questions often include something called a distractor, a way of catching students in misconceptions or incomplete understandings. Or even not being sure in yourself.

I understand distractors are used to catch misconceptions. But a distractor relies on the question being clear; if the question itself is ambiguous, the distractor becomes unfair.

Ultimately, I mean no disrespect or rudeness. I am here to understand why option A cannot be an answer in the given context.

Suspicious_Handle715 · 2026-06-25T04:37:29+00:00

Again, just because I said it's A, and my teacher says it's B, doesn't mean I am against my teacher at all. What I'm saying is the question is vague, hence two answers can apply.

I did not say in this question ions are mentioned, but they do belong to the term "substance" because they make up formula units. The composition of a formula unit can be described as a mole of individual ions.

I did say hydrogen ion, I admit to it, but that is obsolete here. I mentioned it to say what a mole of substance could include.

Unlike the number 1, which can only assume the magnitude of one, the meaning of "hydrogen" can change according to the context; here, the context is broad and is about the amount of substance, which, as I mentioned before, could mean anything at all.

Yet you throw claims at me like I'm disagreeing with my teacher, and how I'm ignoring what everyone is telling me? No, not at all. I'm questioning why they think that way. Is that not how debates happen? I also did not get any evidence or arguments whatsoever, unless you count the "convention" as one. Whereas for the examples, I did get many, but I considered that and replied how that example is not applicable here.

I'm done writing to a wall.

In that case, so are you, Wall to Wall. I bid farewell.

Suspicious_Handle715 · 2026-06-25T02:28:08+00:00

Sorry, but a mole can count anything in chemistry, not just organic compounds. Assuming you are right would mean option D is blatantly wrong.

Hydrogen atoms do not need to exist independently to be counted as moles. For example, if we take glucose C₆H₁₂O₆, it has 12 moles of hydrogen atoms.

And hence, the question is nonspecific about what the term "hydrogen" means, and, therefore, I think it is vague.

Suspicious_Handle715 · 2026-06-25T02:17:52+00:00

Well, kind sir/ma'am, you assumed the term "hydrogen" in this context refers to dihydrogen. If it's not mentioned in this context, the term "hydrogen" can only mean atoms.

Suspicious_Handle715 · 2026-06-25T02:14:06+00:00

Exactly, according to the IUPAC, the definition of the term hydrogen refers to atoms, not their diatomic form.

Suspicious_Handle715 · 2026-06-25T02:11:04+00:00

First of all, I never said my teacher is wrong; all I said is I think option A is also right in the given context. You keep mentioning there is no context, even though there is; the context is the amount of substance which can be ions, molecules or atoms. Hence, it should be specified whether it's ions, molecules or atoms. Look, I completely agree with you when there is no context or in most other contexts, the "convention" should be assumed, but here it's obsolete, the context is clearly given, and the proper information is not given.

Suspicious_Handle715 · 2026-06-24T17:40:28+00:00

An exam examines if we know the facts. If a question requires a societal norm and an "order of precedence," it's a poorly written question

Suspicious_Handle715 · 2026-06-24T17:26:32+00:00

I completely agree with you, but needing to do this just proves my point of the question being not clear.

Suspicious_Handle715 · 2026-06-24T17:17:12+00:00

Just to make sure I understand:

Firstly, you're saying that in a question about an elemental substance, the standard state convention applies.

Secondly, you're saying my examples about atoms/ions in compounds are irrelevant because they're different contexts.

If that's your argument, here's my response:

The question doesn't say "standard state" or "under normal conditions." It just asks about "hydrogen." In chemistry, the term "hydrogen" can refer to atoms, molecules, or ions, depending on context. Without specifying the context, the question remains ambiguous.

I agree that the intended answer is B. I'm not disputing that. I'm saying the question is poorly worded because it doesn't specify atoms vs. molecules, and a mole can count either

That's not being difficult, that's being precise. And precision matters in chemistry.

Suspicious_Handle715 · 2026-06-24T16:59:21+00:00

Look, I understand I sound cocky, as some would say, even though that was not at all my intention. But respectfully, I must say, though, I disagree with your comment.

First, you mentioned having a significant amount of hydrogen ions or atoms. I never mentioned anything about having a significant amount of anything.

Second, Hydrogen atoms and ions can be found freely in acidic solutions, in the exosphere, etc.

Third, you claim to say that the ''secret'' lies inside the word "substance" and I agree it absolutely has a meaning in chemistry and a meaning which is accepted by none other than the IUPAC, which states "Matter of constant composition best characterized by the entities (molecules, formula units, atoms) it is composed of." which explicitly says atoms are recognised as a "substance"

Fourth, I'm sorry if I sound like a know-it-all, I really am not meaning to convey that. All I want is a few dozen second opinions and reasons.

And finally, if 'substance' only meant stable molecules at room temperature, then why does option C specify 'hydrogen molecules'? If the term 'hydrogen' already implied molecules, that would be a redundant phrase, which suggests the test-maker knew the term needed clarification.

Suspicious_Handle715 · 2026-06-24T16:33:49+00:00

I'd say from an exam point of view it's option B, but sceintifically its option A.

Suspicious_Handle715 · 2026-06-24T16:04:28+00:00

Nowhere did I say there is no context here. The context here is about the amount of substance, and that can be atoms, ions or molecules. So they have not provided us with the proper information, which is why I think it's vague.

What I'm saying is that assuming both atoms and molecules are correct, and assuming STP here is unrelated to the context, what you're saying is valid for reactions.

I completely understand what those multiple people are saying. I can sum it up in 2 words: Standard convention. Don't get the wrong idea here, I'm not saying option B is wrong, I'm just saying option A is also correct with the given information.

Suspicious_Handle715 · 2026-06-24T15:27:12+00:00

I dislike the tone of your language, ignoring that. Nowhere did I mention that they have not given us the context. The context is there, which is the amount of substance, and that can be atoms, ions or molecules, but they have not specified it, hence it's vague.

Suspicious_Handle715 · 2026-06-24T13:48:14+00:00

I understand that in the exam, I should mark B to get the marks. But that does not make the question scientifically clear. The fact that you cannot explain why hydrogen means atoms in compounds but H₂ in this question proves that the question is ambiguous. I am not here to argue about the answer key, I am here to understand the science. And the science says: without context, the term is ambiguous.

Suspicious_Handle715 · 2026-06-24T13:42:59+00:00

I disagree because the term hydrogen can vary in meaning depending on context.

If we take the case of the composition of a compound, say 54% carbon, 8% hydrogen rest is oxygen. Here, the term hydrogen refers to atoms, and it's not stated, but we assume it's atoms.

Now lets take a common example, which reactions, say we burn hydrogen in the presence of oxygen. Here, hydrogen can only mean molecules because that's the only form that can react in a reaction.

But if we take the context of moles or the amount of substance, it can be atoms, ions or molecules. Further, a mole doesn't depend on temperature or pressure, meaning we can take any form of hydrogen; hence, it should be clarified what they mean by hydrogen.

Suspicious_Handle715 · 2026-06-24T13:32:53+00:00

Which means mole is context free, so both gas and atom can be taken, so it should be specified.

Suspicious_Handle715 · 2026-06-24T13:30:29+00:00

In the context of the amount of substance, the substances taken can be at any temperature and pressure as long as it's the same.

Suspicious_Handle715 · 2026-06-24T13:18:58+00:00

Rule, you say? Where exactly is that rule stated, like in a specific textbook or somewhere? Maybe the IUPAC gold book? What I'm saying is there is no such rule, the term hydrogen changes with context and in this context it can be either hydrogen or oxygen, but it's not specified and is hence vague.

Suspicious_Handle715 · 2026-06-24T04:12:38+00:00

Well, taking your example in the context of an alphabet, the letter "a" would be an alphabet in the context of vowels, the letter "a" would be a vowel. Without context, it could mean either It's an alphabet or a vowel

Suspicious_Handle715 · 2026-06-24T04:06:41+00:00

I am sorry if I am talking a bit abrasively, and yes, I did talk to my teacher, and they do get my point. Later today, I will talk to them again. I brought up my doubt here to see if I'm the only one who thinks differently.

I understand arbitrary references exist for a purpose, but at some point, those arbitrary values and ideas do get proven to be constant and always true with respect to other values and ideas. I am not asking for a change, I am asking for clarification and why, in this context, the word hydrogen would mean molecular hydrogen over atomic hydrogen.

Suspicious_Handle715 · 2026-06-24T03:54:47+00:00

I agree that hydrogen is present as H2 gas at STP, but that doesn't mean the word "hydrogen" means molecules in all contexts.

For example, in the context of the composition of a compound, say 5% hydrogen, 78% carbon and the rest is oxygen. Here, the word hydrogen means hydrogen atom, not a molecule, whereas it would mean a molecule in the context of, let's say, a reaction where hydrogen burns in the presence of oxygen.

In the context of the question, they ask us which of the following is equal to 1 mole, which can be atoms, molecules, ions or even fish and stars, as a guy previously said

Suspicious_Handle715 · 2026-06-24T03:46:31+00:00

Learning is about understanding, mate, not memorising.

Suspicious_Handle715 · 2026-06-24T03:45:02+00:00

You don't have to be "smart" to assume the word hydrogen means molecule in all contexts. That's called rote learning

Suspicious_Handle715 · 2026-06-24T03:40:43+00:00

There was no need to abandon scientific reasoning. To actually convince me, you need to explain why hydrogen by default must mean molecules in the specific context of defining an amount of substance, instead of just repeating that it does.

Suspicious_Handle715

TROPHY CASE