Troquei a fronha e pus o despertador em cima da cómoda.

Both troquei and pus are in the pretérito perfeito simples in Portuguese, which is the usual tense for a completed action in the past.

• troquei = I changed / I replaced
• pus = I put

So the sentence describes two finished actions:

• first, changing the pillowcase
• then, putting the alarm clock on top of the chest of drawers

For an English speaker, this usually matches the simple past:

• I changed the pillowcase and put the alarm clock on top of the chest of drawers.

Pus is the 1st person singular past form of the verb pôr (to put), and pôr is irregular.

A few important forms are:

• pôr = to put
• ponho = I put / I am putting
• pus = I put
• posto = put

So pus is just the correct past form, even though it looks quite different from the infinitive.

You could also say coloquei o despertador..., because colocar also means to place / to put, but pus is very natural and common in everyday Portuguese.

Yes, it is. This verb is one of those forms you simply need to learn as irregular.

Here are a few past forms of pôr:

• eu pus
• tu puseste
• ele/ela pôs
• nós pusemos
• vocês puseram

So pus = I put.

This is a very useful verb to memorise early, because it appears a lot in everyday speech.

Portuguese often omits the subject pronoun when the verb ending already makes the subject clear.

• troquei already tells you the subject is I
• pus also matches I

So Troquei a fronha e pus o despertador... is perfectly natural.

You could say Eu troquei..., but that usually adds emphasis, contrast, or clarity:

• Eu troquei a fronha, não foi ele.

In neutral speech, leaving out eu is very common.

Portuguese uses definite articles much more often than English does.

So it is very normal to say:

• a fronha = the pillowcase
• o despertador = the alarm clock
• a cómoda = the chest of drawers

Even when English might be less explicit, Portuguese often keeps the article.

This is especially common with:

• everyday objects
• body parts
• possessions
• things already understood from context

So Troquei a fronha sounds natural, whereas leaving out the article would usually sound odd here.

Fronha means pillowcase.

It does not mean the pillow itself.

So:

• almofada = pillow
• fronha = pillowcase

That distinction is important, because Troquei a fronha means you changed the cover, not the pillow.

Trocar often means to change / replace / swap, and it works very naturally for things like clothes, sheets, pillowcases, batteries, and so on.

So:

• Troquei a fronha = I changed/replaced the pillowcase

Mudar also means to change, but it is often used more for:

• changing plans
• moving house
• changing behaviour
• changing position/state

In this sentence, troquei a fronha is the most idiomatic choice.

Em cima de means on top of.

So:

• em cima da cómoda = on top of the chest of drawers

It is formed like this:

• em cima de
  • a cómoda
• de + a = da
• so: em cima da cómoda

This expression is very common when something is physically resting on the upper surface of something else.

Examples:

• O livro está em cima da mesa.
• As chaves estão em cima do sofá.

Because Portuguese normally contracts de + definite article.

Here:

• de + a = da

So:

• em cima da cómoda

Other common contractions are:

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

Examples:

• em cima do armário
• ao lado da cama
• debaixo dos lençóis

These contractions are standard and expected.

Sometimes yes, but the meaning changes slightly.

• na cómoda literally means on/in the chest of drawers, depending on context
• em cima da cómoda clearly means on top of the chest of drawers

If you want to make it explicit that the alarm clock is resting on the top surface, em cima da cómoda is better.

Compare:

• O relógio está na cómoda.
  This can sometimes be understood more loosely.
• O relógio está em cima da cómoda.
  This clearly means on top of it.

So the sentence uses the more precise option.

Cómoda means a chest of drawers or dresser.

In European Portuguese, cómoda is the normal word for that piece of furniture.

A useful spelling note:

• European Portuguese: cómoda
• Brazilian Portuguese: cômoda

So if you are learning Portuguese from Portugal, cómoda is the expected spelling.

The accent mark shows which syllable is stressed.

• cómoda is stressed on the first syllable: CÓ-mo-da

In European Portuguese, that first vowel is open, which is why the written accent matters.

The accent helps you:

1. place the stress correctly
2. distinguish the vowel quality

So the spelling is not optional; it is part of the standard written form.

Yes, the original word order is natural, and you could reverse the two actions if that is the order in which they happened or if you want to present them differently.

Original:

• Troquei a fronha e pus o despertador em cima da cómoda.

Reversed:

• Pus o despertador em cima da cómoda e troquei a fronha.

Both are grammatically fine.

Portuguese usually keeps a fairly straightforward word order here:

• verb
• object
• location

So pus o despertador em cima da cómoda is very normal.

Sometimes, but not always with the same tone.

• pus from pôr = neutral, standard, very common
• meti from meter = often more colloquial, and sometimes less elegant depending on context

For physically placing an object somewhere, many speakers do use meter in everyday speech:

• meti o despertador em cima da cómoda

But pus is a very safe, standard choice and often better for learners.

Because this is just a simple coordination of two actions with the same subject:

• Troquei a fronha
• e pus o despertador em cima da cómoda

In Portuguese, as in English, you do not normally use a comma before e in a simple structure like this.

A comma might appear only for special emphasis, a parenthetical remark, or a more complex sentence.

So the sentence as written is punctuated normally.

Usually yes, that is the natural interpretation.

With trocar plus something like fronha, Portuguese normally suggests:

• removing one
• replacing it with another

So Troquei a fronha naturally means I changed the pillowcase, typically meaning you put a fresh one on.

If you wanted to be more explicit, you could say:

• Troquei a fronha por uma lavada.
• Troquei a fronha por uma limpa.

But in everyday speech, the shorter form is enough.

In this kind of sentence, yes, despertador means alarm clock.

It comes from the idea of waking someone up:

• despertar = to wake up / awaken
• despertador = something that wakes you up

Nowadays it can refer to:

• a traditional alarm clock
• sometimes the alarm function on a device, depending on context

But in this sentence, with em cima da cómoda, it most naturally refers to a physical alarm clock.