What does it mean to standardize the naoh solution why can the molarity of the naoh solution not be determined accurately?

A standard solution is a solution (in this case sodium hydroxide) whose concentration (molarity) is known very precisely. The molarity of the sodium hydroxide solution cannot be determined accurately because s olid sodium hydroxide is highly hygroscopic (absorbs water from the air) and cannot be accurately weighed. Sodium hydroxide form sodium carbonate because it absorbs carbon dioxide from the air.