Overview
- Molarity refers to the number of moles of the solute present in 1 liter of solution. In simple words, 1 mole is equal to the atomic weight of the substance. For example, 1 mole of NaOH is equal to 39.997 g of NaOH (molecular weight = 39.997).
- Hence 0.25 M Sodium Hydroxide means that 9.9992 g of NaOH present in 1 liter of solution.
Calculation procedure
| Parameter | Value |
| Required volume | 1000 mL |
| Molecular weight of NaOH | 39.997 g/mole |
| Concentration of 0.25 M Sodium Hydroxide | 0.9999% (% by mass, wt/wt) |
Preparation
Step 1:
Find out how many g of Sodium Hydroxide you need.
Formula:
(0.25 mol/L) * (39.997 g/mol) = 9.9992 g of Sodium Hydroxide in 1 L.
So to make 1 L solution of 0.25 M NaOH, add 9.9992 g (can be considered 10 g for practical purpose) NaOH to 1 L H2O.
Step 2:
Weigh 10 g NaOH pellets. Pour in to a 1 L volumetric flask containing some water in it. Allow the pellets to dissolve. Add water with constant stirring, make up the volume to 1 Lwith water up to the mark.
Precautions: 1. Use fresh Sodium Hydroxide pellets as the pellets absorb water and CO2 from atmosphere. 2. Sodium hydroxide is caustic and could cause chemical burns. If you do get NaOH on your skin, immediately rinse it with a large volume of water.
Storage
NaOH should be stored in are containers made of HDPE (high density poly-ethylene).
Preparation of Additional Molarities
| Target Molarity | Amount of NaOH (g) |
| 0.1 | 4 |
| 0.5 | 20 |
| 1.0 | 40 |
| 3.0 | 120 |
| 6.0 | 240 |