text: It is common practice in laboratories to make a solution directly from its constituent ingredients.  There are three cases in practical calculation:
  * Case 1: amount of solvent volume is given.
  * Case 2: amount of solute mass is given.
  * Case 3: amount of final solution volume is given.
  In the following equations, A is solvent, B is solute, and C is concentration. Solute volume contribution is considered through the ideal solution model.
  * Case 1: amount (mL) of solvent volume V is given. Solute mass m = C V d /(100-C/d)
  * Case 2: amount of solute mass m is given. Solvent volume V = m (100/C-1/ d )
  * Case 3: amount (mL) of final solution volume Vt is given. Solute mass m = C Vt /100; Solvent volume V=(100/C-1/ d) m
  * Case 2: solute mass is known, V = m 100/C
  * Case 3: total solution volume is known, same equation as case 1. V=Vt; m = C V /100
  Example: Make 2 g/100mL of NaCl solution with 1 L water. The density of the resulting solution is considered to be equal to that of water, statement holding especially for dilute solutions, so the density information is not required.
  :m = C V = ( 2 / 100 ) g/mL × 1000 mL = 20 g
  Chemists often make concentrated stock solutions that may then be diluted as needed for laboratory applications. Standard solutions are those where concentrations of solutes are accurately and precisely known.