【单选题】某箱产品共 20件,已知其中含有4件次品,其余为合格品.现每次从箱中抽出5件,若恰好有2件次品,有( ) 种抽法。
【单选题】用25ml移液管量取25ml溶液,其准确体积应为
【判断题】孟子提出性善论,进一步完善儒家孝道的哲学基础。
【单选题】A 25.0 mL sample of 0.15 M silver nitrate, AgNO3, is reacted with a 3.58 g sample of calcium chloride, CaCl2 (M = 111.0). Which of the following statements is true?
A.
Silver nitrate is the limiting reactant and calcium nitrate precipitates.
B.
Silver nitrate is the limiting reactant and silver chloride precipitates.
C.
Calcium chloride is the limiting reactant and calcium nitrate precipitates.
D.
Calcium chloride is the limiting reactant and silver chloride precipitates.
【单选题】Na2CO3可形成三种水合盐:Na2CO3·H2O、Na2CO3·7H2O、NaCO3·10H2O,在常压下,将Na2CO3投入冰-水混合物中达三相平衡时,若一相是冰,一相是Na2CO3水溶液,则另一相是:
【单选题】一般而言,轮胎使用建议其使用寿命是( )左右