WASHINGTON — After six days of carefully choreographed oral arguments, President Trump’s impeachment trial is about to enter a volatile phase as senators are allowed to ask whatever they want of House prosecutors and White House lawyers.

It is a moment of opportunity — and peril — for both parties, as 100 senators question the House impeachment managers and Mr. Trump’s legal defense team in as many as 16 hours over two days that could shape the endgame of the trial.

Senator Josh Hawley, Republican of Missouri, wants to ask the leading House manager about the whistle-blower whose confidential complaint about Mr. Trump’s dealings with Ukraine touched off the impeachment inquiry, and about Hunter Biden, whom the president asked Ukraine’s president to investigate. Senator Angus King, independent of Maine, plans to question the defense lawyer Alan M. Dershowitz’s criteria for impeachment. Senator Kevin Cramer, Republican of North Dakota, is seeking more information about the president’s personal lawyer, who played a central role in his pressure campaign on Ukraine.

“I’m a little bit curious about Rudy Giuliani,” Mr. Cramer said.

The questions, which will begin Wednesday afternoon and could go late into the evening, will allow senators, who have been sitting restlessly in the Senate chamber for more than a week listening to dueling presentations from the two sides, the chance to participate in the proceedings, albeit indirectly. Under the arcane rules of impeachment, they are to submit written queries that will be read aloud by Chief Justice John G. Roberts Jr., who is presiding over the trial.