Learn Hardcore Chinese: tā bǎ shǒujī fàng zài jiā lǐmiàn.

It introduces the “ba-construction”: S + 把 + Object + Verb + result/location complement. It pulls the object (手机) in front of the verb (放) and highlights how the object is handled and what the outcome is—in this case, that it ends up at a specific place (在家里面).

Is 把 required? Are there natural alternatives without 把?

Not strictly, but 把 is the most natural choice for “put + to a place.” Alternatives:

Colloquial SVO: 她放手机在家里。 This is common in speech but less preferred in careful writing.
Focus on the result (no agent): 手机在家里了。 “The phone is at home (now).”
Passive: 手机被她放在家里了。 Emphasizes the phone rather than the doer, and can sound complaint-like. Avoid “她在家里放了手机” if you want to specify where the phone was put; with 放 you normally include a place or a result like 下/好.

Where should 了 go, and what’s the difference between 放在了 and sentence‑final 了?

她把手机放在家里了: sentence‑final 了 marks a new situation/result (“now it’s at home”).
她把手机放在了家里: 了 after 放 marks completion of the action.
Both sometimes appear together in speech for emphasis: 她把手机放在了家里了. In writing, many teachers suggest using just one.

What’s the difference between 放在, 放到, and 放进?

放在: neutral; emphasizes the final location. 她把手机放在家里。
放到: highlights the movement and reaching the destination. 她把手机放到家里了。
放进: “put into/inside,” used with container-like places. 她把手机放进包里了。 With 家里, 放进家里 is possible but less common than 放在/放到.

Do I need 里面? How does 家里面 differ from 家里, 家中, etc.?

家里: the most common and natural.
家里面: also fine; slightly more explicit/colloquial “inside the home.”
家中: formal/literary. 她把手机放在家中。 sounds written.
里 vs 里面: minimal difference; 里面 is a bit fuller/explicit. Colloquials like 里边/里头 also occur (家里边, 家里头).

Can I omit 在 and say 她把手机放家里?

Yes, in everyday speech: 她把手机放家里了 is very common. In careful/written Chinese, keep 在: 她把手机放在家里了.

Why is 在 after 放 here? Isn’t 在 a verb meaning “to be at”?

Here 在 is a preposition introducing the location complement of the action: 放在 + place = “to put at/in (place).” When 在 is the main verb it means “to be located at” (e.g., 我在家). After action verbs like 放/放在, 在 marks the end location of the action.

Does 把 require the object to be definite/specific?

Yes. 把 typically takes a specific, known object. Here, 手机 is understood as “her phone,” so it’s specific. Using something like 一个手机 with 把 often feels odd unless it’s further specified (e.g., 她把一个新买的手机放在家里了 is acceptable because it’s uniquely identified by “newly bought”).

Can I move the place phrase before 把, like 她在家里把手机放了?

You can place the location before 把, but the verb should still have an appropriate result/complement. Better:

她在家里把手机放下了。 (result: 放下)
她在家里把手机放在桌子上了。 (explicit place) “她在家里把手机放了” is usually felt incomplete unless the context implies a result.

How do I negate this?

Past-like negation: 她没(有)把手机放在家里。 (no 了)
Prohibitive: 别把手机放在家里。/ 不要把手机放在家里。 (don’t do it)

How do I express “left it at home” intentionally vs by mistake?

Intentionally leave behind: 她把手机留在家里了。
By mistake/forgot: 她把手机忘在家里了。 (also: 她把手机落(là)在家里了)

What’s the difference between 在家 and 在家里 here?

Both can work; 在家 is shorter and very common in speech. 在家里 is a bit more explicit (“inside the home”). With 放, 在家里 is the safest choice in careful usage, but you’ll hear 放在家 too in conversation.

Do I need to say 她的 (her) before 手机 or 家?

Not if context makes it clear. 她把手机… is normally understood as “her phone.” To specify someone else’s, add possessors: 她把弟弟的手机放在他家里了。

If I need to count “phone,” what measure word should I use?

Standard: 一部手机 / 一台手机
Colloquial but less standard: 一个手机

Pronunciation: any tips for 里面?

Pronounce the whole sentence as: tā bǎ shǒujī fàng zài jiā lǐmiàn. 里 is third tone (lǐ). 面 is often neutral in fast speech (lǐmian), though miàn4 is also heard.

Why is 她把手机在家里面放 wrong?

In a 把-sentence, the verb should follow the object immediately: 把 + 手机 + 放 + (在/到/进 + place). You can’t insert the location phrase between the object and the verb.

Can I just say 家 without 里/里面?

In speech, yes: 她把手机放在家了/放家里了 both occur, with 放家里 more natural. In careful writing, prefer 家里/家里面.

Is the passive with 被 natural here?

It’s grammatical: 手机被她放在家里了, but use it when you want to spotlight the phone/result or sound a bit complainy/affected. For neutral narration of what she did, the 把-version is more natural.