What is how long does it take to write 2500 words?

It's impossible to give a definitive time for writing 2500 words, as it heavily depends on several factors:

Typing Speed: A faster typist will naturally complete the task quicker. Average typing speeds range from 40-80 words per minute (WPM).
Familiarity with the Subject: Writing about a well-known topic requires less research and planning, significantly speeding up the process. Unfamiliar topics necessitate considerable research, slowing things down.
Research Required: Extensive research increases writing time, especially if sources are difficult to locate and analyze.
Planning and Outlining: A detailed outline ensures a structured writing process, reducing time spent on rearranging content and ensuring a cohesive flow.
Editing and Proofreading: Time must be allocated for revising, editing, and proofreading the document to eliminate errors and improve clarity.
Distractions and Focus: Interruptions significantly prolong writing time. A focused environment is crucial for productivity.

Estimates:

Fastest Possible: A skilled writer, familiar with the subject, with a fast typing speed, and minimal research, could potentially write 2500 words in 3-5 hours (assuming minimal editing).
Average: For the average writer, on a moderately familiar topic, with some research and editing, 6-12 hours is a more realistic timeframe.
Slower/More Complex: For complex topics requiring extensive research and multiple revisions, or for writers with slower typing speeds, it could take 12+ hours, spread over several days.

In summary, preparation, subject knowledge, and typing speed are all vital factors that influence the estimated time.