OVERVIEW
- A 45% (w/w) concentrated Potassium hydroxide solution is a clear colorless liquid that can be purchased from several commercial suppliers.
- % refers to solution concentration in percentage and “(w/w)” refers to solute and solvent amount given in grams (i.e., percentage by weight). This means a 45% (w/w) Potassium hydroxide solution contains 45 g of KOH per 100 g of Potassium hydroxide solution.
- The density of 45% (w/w) Potassium hydroxide solution is 1.456 g/ml at 25°C which means that the weight of the 1 ml of Potassium hydroxide solution is 1.456 g at 25°C.
- 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 KOH is equal to 56.11 g of KOH (molecular weight = 56.11).
Calculation procedure:
| Known values | |
| Density of Potassium Hydroxide | 1.456 g/ml |
| Molecular weight of KOH | 56.11 g/mole |
| Concentration of Potassium Hydroxide | 45% (% by mass, wt/wt) |
Step 1: Calculate the volume of 100 g of Potassium Hydroxide.
Formula:
Density = weight / volume or
Volume = weight / density or
Volume of 100 g of Potassium Hydroxide : 100/1.456 = 68.6813 ml
Note: 45% (w/w) Potassium Hydroxide means that 100 g of Potassium Hydroxide solution contains 45 g of KOH.
The volume of 100 g of Potassium Hydroxide is 68.6813 ml. This means 45 g of KOH is present in 68.6813 ml of Potassium Hydroxide.
Step 2: Calculate how many grams of Potassium hydroxide is present in 1000 ml of Potassium Hydroxide solution.
68.6813 ml of Potassium Hydroxide contain = 45 grams of KOH
1 ml of Potassium Hydroxide will contain = 45/68.6813 grams of KOH
1000 ml of Potassium Hydroxide will contain = 1000 x 45/68.6813 = 655.2 grams of KOH
1000 ml of Potassium Hydroxide will contain 655.2 grams of KOH
Step 3: Calculate the number of moles of Potassium Hydroxide present in 655.2 g of Potassium Hydroxide solution.
56.11 grams of KOH is equal to 1 mole.
1 gram of KOH will be equal to 1/56.11 moles.
655.2 grams will be equal to = 655.2 x 1/56.11 = 11.677 moles
Therefore, we can say that 1 liter of Potassium hydroxide solution contains 11.677 moles or in other words molarity of 45% (w/w) Potassium Hydroxide is equal to 11.677 M.
Calculator – Calculate the molarity of concentrated Potassium Hydroxide (KOH)
Use Calculator to calculate the molarity of concentrated Potassium Hydroxide (KOH) when concentration is given in % by mass (w/w)
Molecular weight of Potassium Hydroxide (KOH) : 56.11 g/mol
(Change the % (wt/wt) concentration)
Density of glacial Potassium Hydroxide: g/ml
Molarity of Potassium Hydroxide: 11.677 M
(Change the density)
Good, but you accidently put HCl in one of the blue arrows in the flow chart. It should be KOH.
Thanks!