Short answer: "Où est-ce que ma chaise est ?" is correct.

Long answer: "est-ce que" is used in order to keep the order between the subject and the verb.

For "Ma chaise est là." the following sentences are correct:

• "Où est ma chaise ?"
• "Où ma chaise est-elle ?"
• "Où est-ce que ma chaise est ?" (may sound weird)
• "Où est-ce qu’est ma chaise ?" (may sound weird)

As a native I would say :

• Où est-ce qu’est ma chaise?
• Où est ma chaise?

I think you do not say Où est-ce que ma chaise est? or at least I never hear people using it.

Maybe because it is not a pronom, because Où est-ce qu'elle est? is used.

Maybe because there is nothing behind because Où est-ce que ma chaise est passée? is also used.

I do not know the rule behind it but it sounds very wrong to me.

“Ma chaise est où?” is not correct formal. If you want to ask a question, you need to inverse the verb and the noun : “Où est ma chaise?”, like you said.

You can ask questions without the question mark, these are called “Phrase interrogative passive (ou indirecte)” or something really close to that. For example : “J’aimerais savoir où se trouve ma chaise.” is a question, “without a question”.

If you want more advice regarding “est-ce que”, you can follow this link.

“Où est-ce que tu vas?” and “Où est-ce que ma chaise est?” are both incorrect. In a direct interrogation sentence, as I said earlier, verb and noun need to be reversed. It is not the case here, as “tu” comes before “vas” and “ma chaise” comes before “est”.

We could try to flip this direct interrogation to an indirect interrogation, but in this case, as pointed in the link I… linked.. earlier, you cannot use “est-ce que” in an indirect interrogation.

The correct syntax is therefore : “Où est ma chaise” and “Où vas-tu?”.

Obviously, this is the formal grammar, but in everyday’s life we use pretty much all of the formulations given in the answer.

No, “Où est-ce que ma chaise est?” is not correct French. I don’t have a grammatical explanation for it, just my native intuition. It sounds weird, I wouldn’t expect a native speaker to say it. I think the weirdness comes from having the verb être at the end of the sentence, which apparently clashes with the fact that être always requires a complement (except in philosophy).

For yes/no questions, in informal spoken French, the verb-subject-complement syntax feels stilted and wouldn’t be used, leaving a choice of “est-ce que” and using intonation only to convey that the sentence is a question. For questions that start with a question adverb, the adverb-verb-subject-complement syntax is sometimes acceptable in informal spoken French. You can ask “Où est ma chaise ?” in informal spoken French. In contrast “Où vas-tu ?” is ok but a bit formal, and “Quand viens-tu ?” is very formal. I don’t have a grammatical explanation for this strange difference.

In informal spoken French, you can use the adverb-subject-verb order when the subject is a pronoun. Since informal spoken french lets you use a pronoun and put its antecedent after it in the same sentence, this doesn’t limit what you can express this way.

Où elle est ?   (formal: « Où est-elle ? »)
Où elle est ma chaise ?   (formal: « Où est ma chaise ? »)
Où il va ?   (formal: « Où va-t-il ? »)
Où il va ce type ?   (formal: « Où va cette personne ? »)

There’s no straightforward “est-ce que” construction for “où est ma chaise”. Some of the informal variants of est-ce que do work, mostly with an extra pronoun.

Où c’qu’elle est ma chaise ?
Où qu’elle est ma chaise ?
Où qu’c’est qu’elle est ma chaise ?
Ma chaise, où qu’elle est ?
Où est-ce qu’est ma chaise ?   (sounds a bit weird, but not wrong)
Où qu’est qu’c’est qu’est ma chaise ?

Où est ma chaise?
Où se trouve ma chaise?
Où est-ce que ma chaise se trouve?

Those are the possibilities I’d go for. Maybe Où est-ce qu'est ma chaise might be right, but I can’t imagine a native French speaking person say this.