Lecture
Place 1–2 cm3 of soap solution and synthetic detergent solution into two test tubes, respectively. Close the test tubes with stoppers and shake them. Foaming of the contents is observed in both test tubes. Add 1–2 cm3 of a calcium or magnesium salt solution to each test tube, close them with stoppers, and shake them. In the test tube with soap, a white precipitate forms and no foam appears, whereas in the test tube with the synthetic detergent, foaming persists.
Draw conclusions about the cleaning action of soap and synthetic detergents in hard water.
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