Antes da festa, eu vou passar o aspirador na sala e no quarto.

Because da is a contraction of de + a.

• antes de = before
• a festa = the party
• antes da festa = literally before of the party, but naturally before the party

This kind of contraction is very common in Portuguese:

• de + o = do
• de + a = da
• de + os = dos
• de + as = das

So after antes de, if the next word has a definite article, the forms usually contract.

Vou + infinitive is one of the most common ways to talk about the future in Brazilian Portuguese.

• eu vou passar = I am going to vacuum
• literally: I go to pass

In everyday Brazilian Portuguese, this structure is often more natural than the simple future:

• eu vou passar o aspirador = very common in speech
• passarei o aspirador = correct, but more formal or less conversational

So if you want to sound natural in spoken Brazilian Portuguese, ir + infinitive is a great choice.

Literally, passar o aspirador means something like to pass the vacuum cleaner over a place.

In Brazilian Portuguese, this is a very common way to say to vacuum.

You may also hear:

• aspirar a sala = to vacuum the living room
• passar o aspirador na sala = to run the vacuum in the living room

Both are correct, but passar o aspirador is extremely common in everyday speech.

Portuguese uses articles more often than English.

So o aspirador means the vacuum cleaner, and that is the normal expression in this phrase:

• passar o aspirador

Saying passar aspirador may be heard in some contexts or regions, but passar o aspirador is the standard and safest form for learners.

This is similar to other common expressions where Portuguese prefers an article:

• tocar o piano
• lavar o carro
• fechar a porta

Because na and no are contractions of em + a and em + o.

• em + a sala = na sala
• em + o quarto = no quarto

So:

• na sala = in the living room
• no quarto = in the bedroom

These contractions are very important in Portuguese and happen all the time.

Other examples:

• em + a cozinha = na cozinha
• em + o banheiro = no banheiro

Because Portuguese nouns have grammatical gender.

• sala is feminine, so it takes a
• quarto is masculine, so it takes o

That is why you get:

• na sala = em + a sala
• no quarto = em + o quarto

This grammatical gender does not necessarily match anything logical in English. It is just something you learn with each noun.

A good habit is to learn nouns together with their article:

• a sala
• o quarto
• a festa
• o aspirador

Yes. Portuguese often drops subject pronouns when the verb form already makes the subject clear.

So both are correct:

• Antes da festa, eu vou passar o aspirador na sala e no quarto.
• Antes da festa, vou passar o aspirador na sala e no quarto.

Both mean the same thing.

Including eu can:

• add emphasis
• make the sentence clearer
• sound a bit more explicit

In many everyday contexts, Brazilians would naturally omit it.

In this sentence, it means the vacuuming will happen in those rooms.

So:

• na sala = in the living room
• no quarto = in the bedroom

Portuguese often uses em with rooms to show where an action happens.

If you wanted to focus more directly on the rooms as objects being cleaned, you could also hear:

• vou aspirar a sala e o quarto

But with passar o aspirador, using na and no is very natural.

Yes. Quarto can mean bedroom, but it can also mean room, depending on context.

In this sentence, because it is paired with sala, the most natural meaning is bedroom:

• na sala e no quarto = in the living room and in the bedroom

But in other contexts, quarto could mean a room in a house, hotel, etc.

Examples:

• Meu quarto = my bedroom
• O quarto do hotel = the hotel room

Yes. Antes da festa is a time expression, and Portuguese allows some flexibility with its position.

All of these are possible:

• Antes da festa, eu vou passar o aspirador na sala e no quarto.
• Eu vou passar o aspirador na sala e no quarto antes da festa.

The version with Antes da festa at the beginning sounds very natural if you want to set the time first.

Putting it at the end is also common and can sound slightly more neutral in some contexts.

Antes da festa is the normal and preferred form.

Technically, antes de a festa can appear in some grammatical contexts, especially when avoiding contraction for a specific reason, but in ordinary usage with a noun phrase like this, Brazilians overwhelmingly say:

• antes da festa

So as a learner, you should strongly prefer the contracted form here.

It is especially common and natural in Brazilian Portuguese.

You may also hear other versions, such as:

• aspirar
• usar o aspirador
• passar o aspirador

For a learner of Brazilian Portuguese, passar o aspirador is an excellent phrase to know because it sounds very everyday and idiomatic.

Without contractions, it would look like this:

• Antes de a festa, eu vou passar o aspirador em a sala e em o quarto.

But that sounds unnatural in normal Portuguese. Native speakers contract these forms:

• de + a = da
• em + a = na
• em + o = no

So the natural sentence is:

• Antes da festa, eu vou passar o aspirador na sala e no quarto.

Learning these contractions is essential because they are used constantly in real Portuguese.