[Examination Requirements] Comprehensive application of common metal elements (sodium, magnesium, aluminum, iron, copper, etc.). ) and common nonmetallic elements (hydrogen, carbon, nitrogen, oxygen, silicon, sulfur, chlorine, etc. ).
Hot spot-detection and substance identification of common ions
1. Inspection of common anions (1) uses acid-base indicator for inspection.
(2) test with reagents such as hydrochloric acid.
Carbon dioxide-
3. Add BaCl2 or CaCl2 solution to produce white precipitate, and then add dilute hydrochloric acid to precipitate and dissolve, releasing colorless and tasteless.
Gas.
SO2-
4: First, add enough dilute hydrochloric acid, no precipitate is generated, and then add BaCl2 solution to generate white precipitate.
SO2-
3. Add BaCl2 solution to produce white precipitate, then add dilute hydrochloric acid to give off colorless pungent smell and dissolve magenta.
Liquid fading gas.
(3) Test with AgNO3 (nitric acid acidification) solution.
(4) Use some characteristic reaction tests.
I
: When starch solution and chlorine water are added dropwise, the solution turns blue (or when chlorine water and carbon tetrachloride are added, the carbon tetrachloride layer turns purple).
2. Inspection of common cations
H+
-Drop purple litmus solution, and the solution will turn red.
3. Answer template for ion detection experiment operation
Operation? Phenomenon? Conclusion Sampling and joining? Is there a generation? Yes
For example, check whether the solution contains Fe2++
But does not contain Fe3++
The method is to take a proper amount of solution in a clean test tube and drop a few drops.
KSCN solution does not show blood red, and then a few drops of H2O2 (or fresh chlorine water) are added to the solution, and the solution turns blood red, indicating that the solution contains Fe2++.
But does not contain Fe3++
.
4. Principle of substance identification
(1) The selected method or reagent should be simple and the experimental phenomenon should be obvious.
(2) When using physical methods, they can generally be carried out in the order of observation method → sniffing method → aqueous solution method.
(3) When chemical methods are used, solid heating, water solubility, indicator test and designated reagent method can be used. Liquid can be tested by indicator test method and designated reagent method; The gas can be ignited and the specified reagent can be introduced.