hannou no kakunin wo suru.

It is read:

はんのう の かくにん を する。
hannou no kakunin o suru

A note on pronunciation:

• 反応 = はんのう
• 確認 = かくにん
• を is pronounced お in modern Japanese, even though it is written を
• する = to do

の connects two nouns.

Here, it links:

• 反応 = response / reaction
• 確認 = confirmation / checking

So 反応の確認 means something like:

• confirmation of the response
• checking the reaction
• a check of the response

In other words, の shows that 確認 is about 反応.

確認 is a noun, but it is also a suru-noun.

That means it can act like a verb when combined with する:

• 確認 = confirmation / checking
• 確認する = to confirm / to check

This is very common in Japanese. Many words of Sino-Japanese origin work this way:

• 勉強 → 勉強する
• 連絡 → 連絡する
• 確認 → 確認する

So in this sentence, 確認 is the action noun, and する turns it into an action.

を marks the direct object of the verb.

In 反応の確認をする, the thing being done is 確認.

So the structure is:

• 反応の確認 = the checking/confirmation of the response
• を = object marker
• する = do

Literally, the sentence is close to:

do the checking of the response

That sounds a bit unnatural in English, but it is a normal Japanese structure.

Both are possible.

• 確認する
• 確認をする

They are very close in meaning. In many cases, 確認する is the more compact and more common way to say to confirm or to check.

But 確認をする is also natural, and it can sound:

• a little more explicit
• slightly more formal or procedural
• suitable for instructions, checklists, or step-by-step actions

So 反応の確認をする is not wrong at all. It just has a slightly more noun-based feel, like describing a task or procedure.

Yes, absolutely.

反応を確認する is very natural and probably the more straightforward everyday phrasing.

Compare:

• 反応を確認する = check the response directly
• 反応の確認をする = do a check/confirmation of the response

The difference is subtle. The first is more direct and verbal. The second feels a little more formal, procedural, or task-oriented.

In many real situations, both would be understood the same way.

する is the plain form, sometimes called the dictionary form.

します is the polite form.

So:

• 反応の確認をする。 = plain style
• 反応の確認をします。 = polite style

Using する here can sound like:

• a plain statement
• a note to oneself
• a manual or checklist item
• a heading or instruction

So in isolation, する often has a practical, written, or neutral feel.

Yes. This is completely normal in Japanese.

Japanese often leaves out the subject when it is obvious from context. Depending on the situation, this could mean:

• I check the response
• We check the response
• You should check the response
• Check the response

The exact subject is not stated, because Japanese often relies on context rather than explicitly naming it.

Not necessarily.

反応 is broader than just a spoken reply. It can mean:

• a reaction
• a response
• a response from a system or device
• a physical or emotional reaction

So the nuance depends on context. For example, it could refer to:

• a person’s reaction
• a patient’s response
• a machine’s response
• a chemical reaction result
• an audience reaction

If you specifically meant a verbal answer, other words might be used depending on context, such as 返事 or 応答.

You are right: normal Japanese writing usually does not use spaces like this.

The standard writing would be:

反応の確認をする。

Spaces are often added only in learning materials to make the parts easier to see:

• 反応
• の
• 確認
• を
• する

So the spaced version is for readability, not standard spelling.