Answer analysis test analysis:

Na2CO3 impurity is mixed into sodium hydroxide to prepare standard solution. Because the molecular weight of sodium hydroxide is 40 and the molecular weight of sodium carbonate is 100, two sodium hydroxide molecules are the same as one sodium carbonate molecule when hydrochloric acid is consumed, and the converted standard sodium hydroxide concentration is small, so the determination result is high, and A can be selected;

When reading the end point of titration, look down at the scale of burette, and the actual reading becomes smaller, so the measured concentration is low, so B cannot be selected; The conical bottle with unknown liquid is washed with distilled water, and it is correct to wash without the liquid to be tested, which will not affect the result, so C cannot be selected; When the titration reaches the end reading, it is found that there is a drop of solution hanging from the tip of the burette, so the actual reading is greater than the real reading, so the measurement structure is too large, so you can choose D; If the basic burette is not wetted with standard solution, the concentration of standard sodium hydroxide becomes smaller, so the measured result is larger, so the answer to this question is ADF.

Test location: acid-base titration

Comments: This question examines acid-base titration, which is the focus of college entrance examination over the years. This question focuses on students' analytical energy. This problem is moderately difficult, especially the A-choice analysis is slightly more difficult.