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The chemical formula of KOH is white powder or flake solid. Its melting point is 380 ℃, and its boiling point is 1324 ℃. It has the characteristics of strong alkali and corrosiveness. When exposed to the air, it is easy to absorb water in the air and deliquesce and absorb carbon dioxide to form potassium carbonate. Soluble in water, ethanol, and glycerin. When dissolved in water, alcohol or treated with acid, a lot of heat will be generated.
The following is the preparation method of 30% potassium hydroxide solution:
1. Calculate the proportion of potassium hydroxide and water: take 30% potassium hydroxide solution as an example, then 30 g of potassium hydroxide and 80 g of water are needed.
2. Weigh potassium hydroxide and water and use balance and other relevant instruments to weigh accurately.
3. Slowly pour the potassium hydroxide into the water and stir with a glass until it is even.
4. Calibration: generally, take a quantitative solution and dry it in the oven to the working reference reagent potassium hydrogen phthalate, then dissolve it in the water without carbon dioxide, and calibrate it with phenolphthalein reagent. Pre use calibration.
The concentration of potassium hydroxide standard titration solution, expressed in moles per liter, is calculated according to the following formula:
Where, m -- the accurate value of the mass of potassium hydrogen phthalate, unit: G.
V1 -- volume value of potassium hydroxide ethanol solution, unit: ml.
V2 -- volume value of potassium hydroxide ethanol solution in blank test, unit: ml.
M -- value of molar mass of potassium hydrogen phthalate, in g / mol [M (khc8h4o4) = 204.22]