Eso es totalmente imposible.

Eso means that, but not in the sense of a specific masculine noun like that book. Here it is a neuter demonstrative pronoun, used to refer to:

• an idea
• a situation
• something just mentioned
• something someone did or said

So in Eso es totalmente imposible, eso means something like that / that idea / that situation.

Examples:

• ¿Salir ahora? Eso es imposible. — Go out now? That’s impossible.
• Lo que propone, eso es absurdo. — What he’s suggesting, that is absurd.

Both can mean this/that, but they point to things differently:

• esto = this, something closer to the speaker
• eso = that, something a bit farther away, or something the other person said
• aquello = that over there / that more distant thing

In conversation, eso is very common for referring to something just mentioned by someone else.

For example:

• Person A: Quiero hacerlo hoy mismo.
• Person B: Eso es imposible.

Here eso refers to what the other person just said.

Spanish often uses ser for definitions, identity, and statements about what something is by nature or how it is being classified.

So:

• Eso es imposible = That is impossible

Using ser here makes sense because imposible is being used as a general judgment or classification.

Estar imposible exists, but it usually means something different, such as:

• Está imposible trabajar aquí.
• El niño está imposible hoy.

That kind of estar often suggests a temporary state or behavior. In your sentence, es is the normal choice.

Yes. Imposible is a cognate of English impossible. They come from the same Latin root, so they look and mean nearly the same thing.

The main difference is spelling:

• English: impossible
• Spanish: imposible

Spanish uses only one s sound here in spelling: -sible, not -ssible.

Because it is agreeing with eso, which is a neuter pronoun. In Spanish, when an adjective refers to esto, eso, or aquello, it normally appears in the masculine singular form.

So you get:

• Esto es bueno.
• Eso es imposible.
• Aquello es raro.

Even though eso is neuter, the adjective usually appears in the default masculine singular form.

Totalmente means totally or completely.

Without it:

• Eso es imposible. — That’s impossible.

With it:

• Eso es totalmente imposible. — That’s totally/completely impossible.

So it is not necessary for the grammar. It just adds emphasis.

In Spanish, adverbs like totalmente, muy, bastante, and realmente usually go before the adjective they modify.

So:

• totalmente imposible
• muy difícil
• realmente interesante

That is the normal word order.

You will sometimes hear unusual order for emphasis in some contexts, but Eso es totalmente imposible is the standard and natural phrasing.

Grammatically, a native speaker might understand it, but it sounds unnatural in normal Spanish.

The natural order is:

• Eso es totalmente imposible

If you want a stronger or more idiomatic alternative, you could say:

• Eso es completamente imposible
• Eso es absolutamente imposible
• Eso es del todo imposible

But imposible totalmente is not the usual order.

Yes, sometimes. Spanish often drops words if the context is clear.

• Es totalmente imposible. — It’s totally impossible.

This works when everyone already knows what you are talking about.

But if you want to point clearly to a specific idea, suggestion, or situation, eso is useful:

• Eso es totalmente imposible.

So both are possible; the version with eso is more explicit.

Yes. It is completely natural and standard in Spain.

It sounds:

• clear
• neutral
• normal in speech and writing

It is not especially formal or informal. You can use it in everyday conversation, in discussion, or even in more serious situations.

A broad pronunciation guide is:

EH-so es to-tal-MEN-teem-po-SEE-bleh

A few useful notes:

• Eso: the e is like eh, and so has a clear s
• es is short
• totalmente has the stress on men: to-tal-MEN-te
• imposible has the stress on si: im-po-SI-ble

In natural speech, totalmente imposible often flows together a bit, so you may hear something close to:

totalmenteimposible

That is just normal connected speech.

They mean almost the same thing:

• Eso es imposible. — That’s impossible.
• Eso no es posible. — That isn’t possible.

The second version can sound a little less absolute in some contexts, though often they are interchangeable.

Compare:

• Es imposible llegar a tiempo. — strongly says it cannot be done
• No es posible llegar a tiempo. — also says it cannot be done, but can sound slightly less dramatic depending on tone

Adding totalmente makes the statement even stronger:

• Eso es totalmente imposible.

Yes. Some common alternatives are:

• Eso es imposible. — simpler, very common
• Eso es completamente imposible. — completely impossible
• Eso es absolutamente imposible. — absolutely impossible
• Eso es del todo imposible. — entirely impossible
• No hay manera. — There’s no way. (more idiomatic)
• Eso no puede ser. — That can’t be.

These all have slightly different tones, but they are close in meaning.

Yes, very often. That is one of the main uses of eso.

For example:

• Viajar mañana sin billete? Eso es imposible.
• Terminar todo hoy? Eso es totalmente imposible.

Here eso refers to the whole idea or action, not to one noun.

This is very common in Spanish and is one reason eso is so useful.

Not by itself. It is neutral. Whether it sounds rude depends mostly on:

• tone of voice
• context
• who you say it to

For example:

• Calm tone: Eso es totalmente imposible. — neutral, factual
• Sharp tone: Eso es totalmente imposible. — could sound dismissive or blunt

If you want to sound softer, you could say:

• Me parece totalmente imposible. — It seems totally impossible to me
• Creo que eso es imposible. — I think that’s impossible
• Ahora mismo eso parece imposible. — Right now that seems impossible

Yes, three useful points:

1. Eso often means that idea / that thing you just said
2. ser is the normal verb in Eso es imposible
3. Adverbs like totalmente normally go before the adjective:
   totalmente imposible

So this sentence is a very good model for many similar ones:

• Eso es muy difícil
• Eso es bastante raro
• Eso es realmente interesante