Which of the following is correct for TLC using silica gel as absorbent? A: Higher the absorption activity of absorbent. larger k and smaller Rf B: Higher the absorption activity of absorbent. larger k and larger Rf C: Stronger the polarity of solvent. larger k and smaller Rf D: Weaker the polarity of solvent. larger k an d larger Rf

Which one is correct for description of TLC using silica gel as absorbent? A: Higher the absorption activity of absorbent. larger k and smaller Rf B: Higher the absorption activity of absorbent. larger k and larger Rf C: Stronger the polarity of solvent. larger k and smaller Rf D: Stronger the polarity of solvent. larger k and larger Rf

Erratic is to predictable as exorbitant is to______. () A: small B: implicit C: productive D: absorbent E: reasonable

In the event of a small bunker oil spill on deck occurring while bunkering, you should ____. A.wash down the area immediately with a fire hose B.wash down the area with kerosene C.cover the area with absorbent material D.cover the area with foam

下列哪些关于吸附作用的说法是正确的？ A: 物质从流体相 (气体或液体) 浓缩到固体表面从而达到分离的过程称为吸附作用 (adsorption), 在表面上能发生吸附作用的固体微粒称为吸附剂 (absorbent),而被吸附的物质称为吸附物 (adsorbate) B: 如果在吸附剂和吸附物之间有电子的转移, 发生化学反应而产生化学键, 这种吸附称为化学吸附 C: 当吸附剂和吸附物之间作用力是通过分子间引力 ( 范德华力) 产生的吸附称为物理吸附 D: 物理吸附是可逆的, 可以成单分子层吸附或多分子层吸附, 选择性较差