【简答题】Further, natural dyes tended to be ______in ______and ______quickly. It was against this ______that Perkin's discovery was made.
【单选题】在醋酸—醋酸钠缓冲溶液中,起抵制外加酸作用的是( )
【单选题】下列4组条件中,能判定△ABC∽△DEF的是 [ ]
A.
AB=5,BC=4,∠A=45°;DE=10,EF=8,∠D=45°
B.
∠A=45°,∠B=55°;∠D=45°,∠F=75°
C.
BC=4,AC=6,AB=9;DE=18,EF=8,DF=12
D.
AB=6,BC=5,∠B=40°;DE=5,EF=4,∠E=40°
【单选题】在pH=5.0的醋酸缓冲液中用0.002 mol/L的 EDTA 滴定同浓度的Pb2+。已知: lgK(PbY)=18.0, lgaY(H)=6.6, lgaPb(Ac)=2.0, 化学计量点时溶液中pPb应为
【判断题】Sea dye marker 用来驱赶鲨鱼。