(1) A. Because the boiling point of water is only 100℃, it cannot be heated in a water bath, so A is wrong;

B, because the boiling point of glycerol is higher than 170℃, so b is correct;

C, sand is solid, it is not convenient to control the temperature, C is wrong;

D, because the boiling point of vegetable oil is higher than 170℃, it needs to be heated in vegetable oil in order to control the temperature between 140 ~ 170℃ in the experiment.

So choose BD;

The acetic anhydride produced is toxic and volatile, and the experiment should be carried out in a fume hood or ventilated place.

So, the answer is: fume hood or ventilated place;

(2) Steam distillation can be used to separate and purify organic matter, so the product after steam distillation in Figure 2 is in a three-necked flask; The long glass conduit in device B should extend into the mixture to make the mixture fully contact with water vapor, which is beneficial to the purification of cinnamic acid.

So the answer is: produce water vapor; Making the mixture fully contact with water vapor is beneficial to the purification of cinnamic acid; Three-necked flask;

(3) When the temperature is low, the solubility of sodium cinnamate will decrease and crystals will precipitate. Therefore, the purpose of thermal filtration is to prevent sodium cinnamate from crystallizing out and blocking the funnel. The specific method is to use a hot filter funnel or take heat preservation measures.

Therefore, the answer is: to prevent sodium cinnamate crystal precipitation from blocking the funnel; Use hot filter funnel or take heat preservation measures;

(4) Hydrochloric acid is a strong acid, so the purpose of adding 1: 1 hydrochloric acid is to convert cinnamic acid into cinnamic acid; After putting the filter paper smaller than the inner diameter of the Buchner funnel, firstly, wash the bottle and squeeze out a small amount of distilled water to wet the filter paper, then turn on the tap and suck lightly, so that the filter paper is close to the funnel porcelain plate, and then turn on the tap to suck and filter. Option B is incorrect, and other options are correct.

So the answer is: convert cinnamic acid into cinnamic acid; ACD

(5) The mass of 5ml benzaldehyde and 14mL acetic anhydride are 1.06g/ml×5ml=5.3g,14ml×1.082g/ml =15. The amounts of the two substances are 5.3g÷ 106g/mol=0.05mol,15.148g ÷102g/mol = 0.15mol respectively, so according to the equation,

So the yield is: 3.1g7.4g×100% = 41.9%,

So the answer is: 4 1.9%.