Preparation From Constituent Ingredients
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 ideal solution model.
- Case 1: amount (mL) of solvent volume VA is given. Solute mass mB = C VA dA /(100-C/dB)
- Case 2: amount of solute mass mB is given. Solvent volume VA = mB (100/C-1/ dB )
- Case 3: amount (mL) of final solution volume Vt is given. Solute mass mB = C Vt /100; Solvent volume VA=(100/C-1/ dB) mB
- Case 2: solute mass is known, VA = mB 100/C
- Case 3: total solution volume is know, same equation as case 1. VA=Vt; mB = C VA /100
Example: Make 2 g/100mL of NaCl solution with 1 L water Water (properties). The density of resulting solution is considered to be equal to that of water, statement holding especially for dilute solutions, so the density information is not required.
mB = C VA =( 2 / 100 ) x 1000 =20 g
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