No hi ha mantega a casa, però sí que hi ha melmelada.

Hi ha means there is / there are.

Catalan normally uses haver-hi for existence:

• Hi ha mantega = There is butter
• Hi ha melmelada = There is jam

It does not usually use ser or estar for this idea.
Those verbs are used for other things, such as identity, description, or location of a specific thing.

So this sentence is about whether something exists or is available at home, which is why hi ha is the right choice.

Hi is a little pronoun that originally has a locative sense, something like there.

In modern Catalan, hi ha is basically a fixed expression meaning there is / there are. So learners should usually think of it as one unit.

That is why:

• Hi ha mantega
• No hi ha mantega

sound natural, while leaving out hi would be wrong in standard Catalan.

Because in Catalan, hi is still part of the existential construction haver-hi, even when the place is stated separately.

So:

• No hi ha mantega a casa
• A casa no hi ha mantega

are both normal.

To an English speaker, this can feel a bit redundant, because English usually just says There isn’t any butter at home. But in Catalan, the hi stays.

In standard Catalan, hi ha usually stays the same even with plural nouns:

• Hi ha una poma = There is an apple
• Hi ha dues pomes = There are two apples

So even with plurals, standard Catalan normally uses hi ha, not hi han.

You may hear pluralized forms in some informal speech, but for learners, hi ha is the safe standard form.

Because here they are being used as mass nouns in a general, non-specific way.

• No hi ha mantega = There isn’t any butter
• Hi ha melmelada = There is some jam

This is very common in Catalan. When you are talking about whether something is available, you often do not use the article.

If you added an article, it would usually make the noun sound more specific:

• la melmelada = the jam
• la mantega = the butter

So the version in the sentence is the natural one for general availability.

A casa is the normal idiomatic way to say at home or at someone’s house.

So:

• Som a casa = We are at home
• No hi ha mantega a casa = There isn’t any butter at home

By contrast, a la casa usually sounds more like at the house / in the house as a physical building, and is less idiomatic for the general idea of home.

Sí que adds emphasis or contrast.

Here, it means something like:

• but there really is jam
• but there definitely is jam
• but jam, there is

It is especially common after a negative statement:

• No hi ha mantega, però sí que hi ha melmelada

So the speaker is contrasting two facts:

• no butter
• yes, jam

The que here is not translated literally as that. It is just part of this emphatic pattern.

Yes. That would still be correct:

• No hi ha mantega a casa, però hi ha melmelada.

This version is more neutral.

The original:

• però sí que hi ha melmelada

is stronger and more contrastive. It sounds like the speaker is correcting an expectation or highlighting the positive part more clearly.

So both are possible, but sí que gives extra emphasis.

In Catalan, no normally goes before the verb, and clitic pronouns like hi stay attached to the verb.

So the order is:

• no + hi + ha

That gives:

• No hi ha mantega

This is the regular Catalan pattern for negation:

• No en tinc
• No hi vaig
• No hi ha pa

So No hi ha is exactly what you should expect.

Yes. That is also natural Catalan.

Compare:

• No hi ha mantega a casa
• A casa no hi ha mantega

Both mean the same basic thing, but the focus shifts slightly.

• No hi ha mantega a casa presents the lack of butter first, then adds the location.
• A casa no hi ha mantega emphasizes at home more strongly, perhaps in contrast with somewhere else.

Catalan allows this kind of movement quite naturally, especially with place phrases.