المكون في وعاء الخلط.

Because Arabic often leaves out is/are in the present tense.

So المكون في وعاء الخلط can be a complete nominal sentence meaning the ingredient is in the mixing bowl.
The structure is:

• المكوّن = the subject/topic
• في وعاء الخلط = the predicate, giving the location

This is very normal in Modern Standard Arabic.

It could be either, depending on context.

As a standalone line with a period, it is most naturally read as a full sentence:

• المكوّن في وعاء الخلط. = The ingredient is in the mixing bowl.

But the same words could also function as a noun phrase in a larger sentence:

• المكوّن في وعاء الخلط = the ingredient in the mixing bowl

Arabic often allows this kind of ambiguity, and context usually makes the meaning clear.

In this context, it is most likely المُكَوِّن pronounced al-mukawwin.

Why is that not obvious? Because normal Arabic spelling usually leaves out short vowels and most other vowel marks. So المكون could, in theory, be read in more than one way.

Here, context strongly suggests المُكَوِّن because that commonly means ingredient or component.

So a learner should understand that:

• written form: المكون
• full vocalization: المُكَوِّن
• likely meaning here: the ingredient

It is singular.

• مكوّن = ingredient / component
• مكوّنات = ingredients / components

So this sentence is talking about one ingredient or one component, not several.

في is the preposition in.

So في وعاء الخلط means in the mixing bowl.
This whole prepositional phrase tells you where the ingredient is.

English speakers can think of it very directly:

• في = in
• وعاء = bowl / container
• الخلط = mixing

Because وعاء الخلط is an iḍāfa construction, often called a possessive or noun-link construction.

In an iḍāfa:

• the first noun usually does not take الـ
• the second noun determines whether the whole phrase is definite

So:

• وعاء الخلط literally = bowl/container of the mixing
• because الخلط is definite, the whole phrase is definite

That is why Arabic does not say الوعاء الخلط for this meaning.

Yes. That is the literal structure.

Arabic often expresses compound nouns this way:

• وعاء = bowl / container
• الخلط = mixing

So وعاء الخلط literally means the bowl/container of mixing, but natural English says mixing bowl.

Also, الخلط here is not a finite verb. It is a verbal noun (also called a maṣdar) meaning mixing.

If you wrote it with full vowel marks as a complete sentence, it would be:

الْمُكَوِّنُ في وِعاءِ الخَلْطِ

This shows the grammar clearly:

• الْمُكَوِّنُ = nominative, because it is the subject of the nominal sentence
• وِعاءِ = genitive, because it comes after the preposition في
• الخَلْطِ = genitive, because it is the second term of the iḍāfa

In ordinary printed Arabic, these endings are usually not written, so you normally just see:

المكون في وعاء الخلط