A câmara de ar está vazia.

Because Portuguese uses estar for a state or condition, especially one that can change.

An inner tube can be empty now and full later, so está vazia is the natural choice.

Using é vazia would sound strange, as if being empty were its permanent, defining characteristic.

Because vazia agrees with câmara, which is a feminine singular noun.

In Portuguese, adjectives usually agree with the noun in gender and number:

• câmara → feminine singular
• vazia → feminine singular

Compare:

• o pneu está vazio = the tyre is empty
• a câmara está vazia = the inner tube is empty

No.

• pneu = tyre / tire
• câmara de ar = inner tube

So this sentence is talking about the inner tube, not the tyre as a whole.

Literally, câmara de ar is something like air chamber, but the normal meaning is inner tube.

Because de ar is the normal way to form this kind of noun phrase in Portuguese.

Here, de means something like for / containing / involving air. It identifies the type of câmara.

• câmara de ar = inner tube
• garrafa de água = water bottle
• óculos de sol = sunglasses

Using do ar would mean of the air or from the air, which is not the meaning here.

A is the feminine singular definite article, meaning the.

It is used because the speaker is referring to a specific inner tube, not just any inner tube.

Portuguese often uses definite articles in places where English may or may not use the, so learners usually need to get used to seeing them more often.

If you were introducing it for the first time as an unspecified one, you could say:

• Uma câmara de ar está vazia.

But in normal context, A câmara de ar... is very natural.

Because grammatical gender is a property of the noun itself, and câmara is a feminine noun in Portuguese.

You can see that from:

• the article: a
• the adjective: vazia

This does not mean the object is biologically female. It is just grammar.

A rough European Portuguese pronunciation is:

uh KAH-muh-ruh duh AR esh-TAH vuh-ZEE-uh

A more technical approximation in IPA is:

/ɐ ˈkɐ.mɐ.ɾɐ dɨ ˈaɾ ɨʃˈta vɐˈzi.ɐ/

A few useful points:

• câmara has the stress on the first syllable
• de ar is usually pronounced very smoothly together
• unstressed vowels in European Portuguese are often reduced, so they may sound weaker than you expect

Está vazia is correct and natural.

But in everyday speech, especially when talking about tyres or inner tubes, Portuguese speakers may also say:

• A câmara de ar está sem ar. = The inner tube has no air.
• A câmara de ar está furada. = The inner tube is punctured.

So:

• vazia focuses on the result: it is empty
• sem ar is a very common practical way to say there is no air in it
• furada means there is a hole / puncture

Not necessarily.

Vazia only tells you that it is empty of air.

It might be empty because:

• it has a puncture
• someone let the air out
• it was never inflated

If you specifically want to say it has a puncture, use furada.

Grammatically, yes, but only if the context makes it completely clear.

On its own, câmara can mean several things in Portuguese, such as:

• chamber
• council
• camera, in some contexts

So if you are talking about an inner tube, câmara de ar is much clearer and more natural.

You would say:

As câmaras de ar estão vazias.

Notice how several words change:

• a → as
• câmara → câmaras
• está → estão
• vazia → vazias

This is a good example of agreement across the whole sentence.