That is only true as long as there is no ь in the end, in which case the noun can be either masculine or feminine.
molodets, one can not approach the issue of gender in Russian that way (like in a Romance language) and a good way to look at it is in terms of soft/hard endings, but even that is not so strict.
What you said doens't make any sense to me. What are you trying to say here?
I like the pairing of "whose" and "juice" :D It somehow helps me remember what чей means :)
It doesn't matter whether you say, "Чей это сок?", "Это чей сок?" or "Чей сок это?" - all three options are used and mean the same thing. But the first one is the most common one. And it doesn't sound any more weird than the English "Who are you talking to?" (as opposed to "To whom are you talking?") sounds to a Russian.
Because the sentence would be more accurately rendered as whose juice is this?
"This is", "These are", "Is this" and "Are these" - all of those phrases correspond to the same Russian pronoun "Это". There is also a demonstrative adjective "это" which modifies singular nouns of neuter gender, e.g. "это окно" = "this window". But we say "этот стол" ("this table" - masculine gender) and "эта стена" ("this wall" - feminine gender).
I know all of this, but this one really doesn’t make any sense to me. It’s the word order that’s messing me up. when you say «это стол», subject verb, cool, it works. if you say это чей сок? cool, it works as well. чей сок это, cool as well. but Чей это сок? this word order is weird as all hell. why would you separate “whose” from “juice”? it’s like your asking about это instead of juice.
I also find the word-order problematic, from an English-speaking point of view. Studying Romance languages doesn't help either, where equivalents to Это are often required to agree with the noun they're attached to.
Most of all, though, is the "logic" (not making fun of anyone here, just pointing out why I'm having a little problem here) is that the sentence more or less means "Whose juice is this unknown thing?" when you know perfectly well it's juice. I'm getting used to the lack of agreement between это and everything else, it just seems a bit odd.
PS But even in French, there's an equivalent: c'est (an abbreviation of ce est) and ce sont:
C'est un homme, c'est un femme, ce sont des hommes, ce sont des femmes:
"He is a man, she is a woman, they are men, they are women".
Ce has a lot of uses in French. Like c'est du jus = "It is juice".
Чей and сок are both masculine, so whatever word order is used, it is clear that you are asking about juice, not это.
Almost none. If you’re holding the juice, «Чей это сок?» will be the better option. In general, «Чей сок?» would do.
«Чей этот сок» is the correct sentence since it is referring to the juice. The current sentence is unnatural.
Come on! The given Russian question is not only natural, but it is the commonest thing you can think of. At the same time, your version is marginal as it translates into "Whose is this juice?" How often do you hear that in English? Это is a universal word in question starting with чей, чьё, чья, чьи: "Чьё это полотенце?", "Чья это тарелка?", "Чьи это носки?". In all these questions the word "это" can be moved to the end of the sentence without changing the meaning; however, such a shift will result in a poor rythm so the questions will sound less natural.