Lesson 2. Concentration of Ionic Solutions

The preparation of a solution is a lab procedure that should be learned. Although you will not bet the opportunity to do this at home, you are expected to learn the procedures. 

Steps involved in preparing a solution:

1. Calculate the mass required.
2. Measure out the mass on a scale
3. Place the solid in a clean dry beaker
4. Dissolve the substance in about 1/2 of the final volume
5. Transfer the solution to a volumetric flask. 
6. Rinse all equipment with distilled water 
7. Use a medicine dropper to bring the volume up the line on the flask. The bottom of the meniscus should be on the line.
8. Stopper the flask and invert several times. 

Example: 
Prepare 100 mL of a 0.100 M (mol/L) solution of sodium carbonate. 
Materials:
solid sodium carbonate, 100 mL beaker, scale, scoopula, stopper, funnel, stir rod, a medicine dropper

Procedure: 
1. Calculate the mass
n= CV= 0.100M x 0.100 L = 0.0100 mol 
The molar mass of NaCO₃ is 105.99 g/mol
m= nM = 0.0100 mol x 105.99 g/mol 
m=1.0599 g

2. Place the beaker on the scale, push the tare button to zero the scale with the beaker on it. Measure out 1.06 g

3. Pour about 50 mL of distilled water into the beaker. Stir with a stir rod until all of the solid is dissolved. 

4. Using a funnel, transfer the solution to the volumetric flask. Rinse the beaker and stir rod and funnel with distilled water.

5. Bring volume up to the line using a medicine dropper

6. Stopper the flask and invert at least twice.