What is a standard solution? How is it prepared?

Answer 1

It depends entirely on what the solute is and what the solution is to be used for.

Answer 2

It’s used to calibrate instruments. For example, the standard solutions used to calibrate a pH meter is buffer ph 4.0, 7.0, and 10.0. 

It’s any solutions where you know the precise concentration. You prepare it by weighing out the substance in an analytical scale and dissolving it in a volumetric flask. Say you want to make a 1.0 M NaOH solution so you weight out 40.0000 g of NaOH. Dissolve in a 1 L volumetric flask.