There are three questions in this year's chemical experiment operation examination in our city: ① to explore the chemical properties of acid and alkali; ② preparation and collection of ②CO2; ③ Prepare

There are three questions in this year's chemical experiment operation examination in our city: ① to explore the chemical properties of acid and alkali; ② preparation and collection of ②CO2; ③ Prepare a certain solute mass. (1) According to instruments, diagrams and uses, A is a gas container; So, the answer is: gas cylinders;

(2) When taking potions, attention should be paid to: ① the bottle stopper is upside down, ② the label is aimed at the palm of your hand, ③ the bottle mouth is close to the test tube mouth, so ② it is wrong; When collecting gas by exhausting upward, the air duct should extend to the bottom of the gas container to exhaust the air in the gas container. Therefore, 3 errors; So, the answer is: ② ③;

(3) Check the air tightness. First, immerse the catheter in water, hold the test tube by hand, and observe whether there are bubbles emerging from the nozzle in the water; If bubbles appear, it means that the equipment is not leaking. So the answer is: there are bubbles coming out of the catheter mouth;

(4) The comprehensive calculation process shows that gas is generated and collected, so the answer is: ②.