How to determine the acid in a mixture
How to determine the acid in a mixture
From the point of view of electrolytic theorydissociation, acids are compounds, the dissociation of which forms a positive hydrogen ion H + and a negative ion of the acid residue. Lewis acids are presented in a more general way: they are called all cations, anions or neutral molecules that are capable of receiving electron pairs. The bases of Lewis are capable of giving electronic pairs.
Instructions
1
Indicators are used to determine the acid in the mixture. Reactions of acids with indicators lead to a change in the color of the latter. The qualitative detection of acids in solutions is based on this principle.
2
For example, litmus. Dip a small slice of litmus paper into the solution. In a neutral environment, it will turn purple, turn red in an acidic environment, and turn blue in an alkaline medium. The intensity of the color depends on the concentration of the solution. Litmus is the most widely used acid-base indicator.
3
Another well-known indicator ismethyl orange (methylorange), an organic synthetic dye. Methylorange becomes red in an acidic medium, orange in neutral and yellow in alkaline. When methylorange reacts with substances, its structure changes, and this changes the intensity of absorption of light rays.
4
Congo red turns blue from a strong acid. In a neutral and alkaline environment, it will be red. To determine the alkaline environment, phenolphthalein is often used, which becomes crimson in such conditions. When strongly acid reaction medium phenolphthalein orange. In weakly acidic, neutral and strongly alkaline solutions it is colorless.
5
Qualitative for individual acids areredox transformations, leading to precipitation. Thus, according to the ionic equation Ag (+) + Cl (-) = AgCl ↓, it is possible to determine the hydrochloric acid HCl, because when adding silver cations to the solution, a white precipitate of AgCl ↓ precipitates. A white precipitate also falls out in the equation Ba (2+) + SO4 (2-) = BaSO4 ↓. Silver cations can also be detected orthophosphoric acid H3PO4: 3Ag (+) + PO4 (3-) = Ag3PO4 ↓ (yellow precipitate).
