In this paper, the common instruments and basic operations of chemical experiments are investigated.
A, access to solid drugs, first of all, the test tube should be placed horizontally, and sent to the bottom of the test tube with a paper slot or medicine spoon, so the operation shown in the diagram is wrong;
B, when using liquid: ① reagent bottle bottle mouth should be close to the test tube mouth to prevent liquid from flowing out; (2) The label faces the palm to prevent the liquid from flowing out and corroding the label; (3) the bottle stopper is not placed upside down on the table, which may pollute the bottle stopper and thus the medicine. The operation shown in the figure is correct;
C. When testing the air tightness of the device, the pressure of the gas in the device changes. Bubbles come out, indicating that the air tightness of the equipment is good, otherwise the air tightness is not good and the operation is correct, so it is correct;
D when heating the liquid, the liquid in the test tube should not exceed 1/3 of the volume of the test tube to prevent boiling and splashing, so the operation is correct. So choose one