Ogni sabato passo il mocio sul pavimento del soggiorno.

Because ogni is followed by a singular noun in Italian.

• ogni sabato = every Saturday
• not ogni sabati

This is different from English, where every can also be followed by a singular noun, so the pattern is actually similar.

Italian can also say:

• tutti i sabati = every Saturday / on Saturdays

Both are correct, but ogni sabato is very common and concise.

With ogni, you normally do not use an article.

So you say:

• ogni sabato
• ogni giorno
• ogni settimana

not:

• ogni il sabato

The word ogni already works like every, so no extra article is needed.

Passo here is the first person singular of the verb passare in the present tense:

• io passo = I pass

But in this sentence, passare does not mean just to pass in the usual English sense. With cleaning, it can mean to run something over a surface, so:

• passare il mocio = to mop / to run the mop over

So passo il mocio means I mop or more literally I pass the mop over.

Because the sentence is a complete statement: I mop the living room floor every Saturday.

Italian needs a conjugated verb in a normal sentence, so passare changes to match the subject io:

• io passo = I pass / I mop
• tu passi
• lui/lei passa

So passo is used because the subject is I, even though io itself is not written.

Yes, but that is normal in Italian.

Italian often drops subject pronouns when the verb already makes the subject clear. Since passo clearly means I, you do not need to say io.

So:

• Ogni sabato passo il mocio... = normal
• Ogni sabato io passo il mocio... = also possible, but more emphatic

You would add io only if you want contrast or emphasis.

Il mocio means the mop.

In everyday Italian, cleaning vocabulary can vary a bit by region or preference. You may also hear:

• lo straccio = cloth, rag, sometimes used for floor-cleaning cloth
• il mocio = mop
• il mop = sometimes used too, especially in modern usage

In this sentence, il mocio is the cleaning tool used on the floor.

Italian uses definite articles more often than English.

So even where English might say:

• I mop the floor

Italian often says:

• passo il mocio sul pavimento

Literally, that includes the mop and the floor.

This is very normal. Italian often prefers:

• il mocio
• il pavimento
• la cucina
• il soggiorno

where English might sometimes leave the article out or structure things differently.

Sul is a contraction of:

• su + il = sul

Here, su means on.

So:

• sul pavimento = on the floor

This fits the idea of moving the mop over the surface of the floor.

Because the mop is being used on the surface of the floor, not inside it.

Italian says:

• passare il mocio sul pavimento
• literally, to pass the mop on the floor

Using su highlights contact with a surface. That is why it sounds natural here.

Del is a contraction of:

• di + il = del

So:

• il soggiorno = the living room
• del soggiorno = of the living room

Therefore:

• il pavimento del soggiorno = the living room floor
• literally, the floor of the living room

Italian commonly expresses this idea with noun + di + noun:

• il pavimento del soggiorno
• la porta della cucina
• il tavolo del salotto

English often uses a noun directly before another noun, as in living room floor, but Italian usually prefers the di structure.

So il pavimento del soggiorno is the normal Italian way to say the living room floor.

Yes, it is very natural.

The sentence structure is:

• Ogni sabato = time expression
• passo = verb
• il mocio = object
• sul pavimento del soggiorno = place/surface

Italian often puts time expressions like ogni sabato at the beginning, just like English can say Every Saturday, I mop...

You could rearrange parts for emphasis, but this version sounds normal and clear.

Yes. A few natural alternatives are:

• Ogni sabato passo il mocio in soggiorno.
• Ogni sabato lavo il pavimento del soggiorno.
• Ogni sabato do il mocio al pavimento del soggiorno.
• Ogni sabato passo lo straccio sul pavimento del soggiorno.

These are not all exactly identical in tone or regional usage, but they are all possible ways to express a similar idea.

The original sentence is understandable and natural, especially if you want to emphasize the action of using the mop.