Его молчание вызвало беспокойство.

Here его means his.

Russian его can mean either:

• him as an object: Я вижу его = I see him
• his as a possessive: его книга = his book

In Его молчание вызвало беспокойство, его modifies молчание (silence), so it means his silence.

A useful point: Russian does not have a separate word for his like English does. The same form его is used.

Молчание is in the nominative case because it is the subject of the sentence — the thing that caused the concern.

So the structure is:

• Его молчание = his silence → subject
• вызвало = caused
• беспокойство = concern / anxiety → direct object

Because молчание is a neuter singular noun.

In the past tense, Russian verbs agree with the subject in gender and number:

• masculine: вызвал
• feminine: вызвала
• neuter: вызвало
• plural: вызвали

Since молчание is neuter, the verb is вызвало.

A very common clue is the ending -ие / -ние.

Words like:

• молчание = silence
• знание = knowledge
• понимание = understanding

are typically neuter.

That is why the sentence uses вызвало, not вызвал or вызвала.

It is in the accusative case, because it is the direct object of вызвало.

The verb вызвать usually takes a direct object: to cause something.

So:

• вызвало что? = caused what?
• беспокойство = concern / anxiety

However, for many inanimate neuter nouns, the accusative looks exactly like the nominative. So беспокойство looks the same in both cases.

Вызвать is the perfective verb, while вызывать is its imperfective partner.

• вызывать = to cause, to be causing, to cause repeatedly/in general
• вызвать = to cause, to bring about once as a completed event

In this sentence, the idea is that his silence caused concern as a completed fact, so вызвало (from вызвать) is natural.

Compare:

• Его молчание вызывало беспокойство.
  His silence was causing concern / used to cause concern.

• Его молчание вызвало беспокойство.
  His silence caused concern.

It can mean any of those depending on context.

Common translations are:

• concern
• worry
• anxiety
• unease

In this sentence, concern is often the most natural neutral translation:

• His silence caused concern.

If the context is more emotional or serious, worry or anxiety may also fit.

Yes. Russian word order is more flexible than English word order.

The neutral order here is:

• Его молчание вызвало беспокойство.

But you could also say:

• Беспокойство вызвало его молчание.

That still means roughly the same thing, but the emphasis changes. The second version puts more focus on беспокойство at the beginning.

English usually depends much more on word order to show who did what. Russian often shows this through case endings and verb agreement instead.

Russian has no articles like a, an, or the.

So Его молчание вызвало беспокойство could be understood as:

• His silence caused concern
• His silence caused the concern

Which one sounds best depends on context. In many cases, plain concern is the most natural English translation.

A careful pronunciation is approximately:

Его молча́ние вы́звало беспоко́йство.

Stress:

• его → usually stressed on the last syllable: его́
• молча́ние
• вы́звало
• беспоко́йство

A rough English-style approximation would be:

yi-VO mol-CHA-ni-ye VYZ-va-la bys-pa-KOY-stva

But it is better to learn it from the stressed Russian form above.

Yes, but it would not mean exactly the same thing.

• молчание = silence in the sense of not speaking
• тишина = silence / quiet in the sense of lack of sound

So:

• Его молчание = his silence / the fact that he said nothing
• Его тишина would sound less natural for this meaning unless you specifically mean quietness rather than not speaking

In this sentence, молчание is the correct and natural choice.

No, его itself stays the same here.

Russian possessive его (his) is indeclinable, so it does not change for the gender, number, or case of the noun that follows:

• его книга = his book
• его письмо = his letter
• его молчание = his silence
• его друзья = his friends

So even though молчание is neuter singular nominative, его remains его.