Hay un cubo azul para el agua y otro para la ropa sucia.

Hay means there is or there are. It is used to say that something exists.

So:

• Hay un cubo azul... = There is a blue bucket/bin...

A very important point: hay does not change for singular or plural.

• Hay un cubo = There is one bucket
• Hay dos cubos = There are two buckets

It comes from the verb haber, but in this use you can think of it as a fixed form meaning there is/there are.

In this sentence, cubo means bucket or bin/container, not the geometric shape cube.

Spanish cubo can mean different things depending on context:

• un cubo = a bucket / bin
• un cubo = a cube

Here, because the sentence talks about one for water and one for dirty clothes, it clearly means a container, not a geometric cube.

In Spain, cubo is very commonly used for a bucket or a bin.

In Spanish, descriptive adjectives usually come after the noun.

So:

• un cubo azul = a blue bucket

This is the normal word order in Spanish:

• una casa blanca = a white house
• un coche rojo = a red car

English usually puts the adjective before the noun, but Spanish usually puts it after.

Otro means another or the other one. In Spanish, the noun is often left out if it is already obvious from context.

So:

• Hay un cubo azul para el agua y otro para la ropa sucia.

literally means:

• There is a blue bucket for the water and another one for the dirty clothes.

The word cubo is omitted after otro because it is understood.

You could also say:

• Hay un cubo azul para el agua y otro cubo para la ropa sucia.

But that sounds a bit more repetitive. The version with just otro is more natural.

Because otro normally does not take the indefinite article un/una.

So Spanish says:

• otro cubo = another bucket

not:

• un otro cubo ❌

This is a very common point for English speakers, because English uses another, which feels like an + other. But in Spanish, otro already carries that meaning by itself.

Para means for here, in the sense of intended for or used for.

• para el agua = for the water
• para la ropa sucia = for the dirty clothes / dirty laundry

The second para is repeated because each container has its own purpose:

• one is for water
• the other is for dirty clothes

Spanish could not normally leave out the second para here without making the sentence unclear or unnatural.

This is a very common question.

Agua is grammatically feminine, but in the singular it usually takes el, not la, because it begins with a stressed a sound.

So:

• el agua
• el águila

But the noun is still feminine. You can see that in adjectives:

• el agua fría = the cold water
• el agua limpia = the clean water

The article changes to el for sound reasons, but the noun itself is still feminine.

In the plural, it goes back to normal feminine articles:

• las aguas

In Spanish, ropa is usually treated as an uncountable or collective noun, like clothing in English.

So:

• la ropa = clothes / clothing
• la ropa sucia = dirty clothes / dirty laundry

Even though English often uses the plural clothes, Spanish normally uses singular ropa.

You can say ropas in some contexts, but it is much less common and usually more specific. In everyday speech, la ropa sucia is the normal expression.

It can mean either, depending on context.

• la ropa sucia = dirty clothes
• la ropa sucia = dirty laundry

In this sentence, because it talks about a separate container, dirty laundry is probably the most natural English interpretation.

Because Spanish does not need it here. The structure is elliptical: some words are left out because they are understood from the first part.

Full idea:

• Hay un cubo azul para el agua y hay otro cubo para la ropa sucia.

But Spanish naturally shortens this to:

• Hay un cubo azul para el agua y otro para la ropa sucia.

English does something similar:

• There is a blue bucket for the water and another for the dirty clothes.

So nothing is missing grammatically; it is just a natural omission.

Grammatically, azul directly describes only the first cubo:

• un cubo azul = a blue bucket
• otro = another one

So the sentence clearly states that the first bucket is blue. It does not explicitly say that the second one is blue too.

If you wanted to say both were blue, you would normally make that clearer, for example:

• Hay dos cubos azules...
• Hay un cubo azul para el agua y otro azul para la ropa sucia.

Yes. Para is the correct choice here.

Use para when you mean:

• intended purpose
• destination
• use

So:

• un cubo para el agua = a bucket for water
• un cesto para la ropa sucia = a basket for dirty laundry

Por would not sound natural here, because por usually expresses ideas like:

• through
• by
• because of
• in exchange for

This sentence is about what each container is for, so para is right.

Yes, it is understandable and natural enough, especially in a practical context.

A speaker in Spain might also choose slightly different nouns depending on the exact object:

• cubo = bucket / bin
• cesta = basket
• cesto = basket/bin
• cubo de la ropa sucia = dirty-laundry bin

But your sentence is perfectly normal if you are talking about two containers, one for water and one for dirty laundry.