Question

Sodium hydroxide is hygroscopic, which is why you were instructed to keep the bottle of sodium hydroxide covered to prevent contact with air. Define the term in bold and explain the error that would occur if you used the mass of NaOH to determine the molarity of the solution instead of standardizing the solution. Clearly indicate whether the error will lead to a molarity that is too high or too low.

Answer 1

Hygroscopic solid means soild when exposed to air it is absorbing moisture from air.

As sodium hydroxide is hygroscopic when it exposed to air it is absorbing moisture from air so it is instructed to keep sodium hydroxide bottle covered to prevent contact of air.

If we used mass of sodium hydroxide instead of standardizing the solution. There will be error due to hygroscopic nature of NaOH. Actual Sodium hydroxide quantity will be less due to moisture present sodium hydroxide so the molarity of prepared solution will be low.