heya ni shuunoukago o oku.

I put a storage basket in the room.

Breakdown of heya ni shuunoukago o oku.

• を: direct object particle
• 部屋へや: room
• に: location particle
• 置おく: to put

Questions & Answers about heya ni shuunoukago o oku.

What does each part of 部屋 に 収納かご を 置く mean?

• 部屋（へや） = room
• に = a particle marking the place where something is put
• 収納かご（しゅうのうかご） = storage basket / storage bin
• を = a particle marking the direct object
• 置く（おく） = to put, place, set down

So the sentence structure is basically:

room + in/into + storage basket + object marker + put

Why is に used after 部屋?

に is used because 置く is a verb that often marks the location of placement with に.

So in this sentence:

• 部屋に = in the room / into the room

It tells you where the basket is being placed.

This is different from を, which marks what is being placed.

Why is を used after 収納かご?

Because 収納かご is the thing being acted on by the verb 置く.

In other words:

• 収納かごを置く = place the storage basket

The particle を marks the direct object, so it answers the question what is being placed?