How to Use Volumetric Flasks
A volumetric flask is laboratory analytical glassware used for the preparation of solutions with the exact volume. Such a flask comprises a flat-bottomed bulb and a long neck. There is a ring graduation volume mark in the neck part of the flask. This glassware is available in a variety of sizes but flasks for 25, 100, 250, 500 and 1000 ml are commonly used in the laboratory practice. As an example, consider making 500 ml of the 2 molar solution of sodium hydroxide (NaOH) using the volumetric flask.
Other People Are Reading
Instructions
-
-
1
Multiply the molarity by the volume of the solution and the molar mass of the compound to calculate the mass of the substance needed. In our example, the molar mass of sodium hydroxide is 40 g/mole and the solution volume is 0.5 L (500 ml). The mass of sodium hydroxide is 2 mole/L x 0.5 L x 40 g/mole = 40 g.
-
2
Weigh the calculated amount of the compound (step 1) on the analytical scale. Carefully transfer sodium hydroxide into the "500 ml" volumetric flask.
-
-
3
Add about 400 ml of the distilled water into the volumetric flask. Gently swirl the flask until the sodium hydroxide gets completely dissolved.
-
4
Add the distilled water slowly to the volumetric flask until the level of the liquid almost reaches the volume mark on the flask neck.
-
5
Fill in the plastic pipette with the distilled water.
-
6
Lift the volumetric flask to bring the volume mark to the eye level. You will see the curved solution meniscus.
-
7
Add the distilled water from the pipette drop by drop until the bottom of the solution meniscus lines up exactly with the volume mark.
-
1
