WASHINGTON — The government will examine thousands of Hillary Rodham Clinton’s emails for public release — and for possible security lapses — after revelations she used a private account to conduct official business as secretary of state, a senior State Department official said Thursday. Clinton’s extensive use of private emails has raised questions in the buildup to her expected presidential run about whether she adhered to the letter or spirit of accountability laws. The official said the department would review 55,000 pages of emails amassed from Clinton’s personal files to determine if there were any instances where she improperly transmitted sensitive information.