停止加热时,应遵守的原则是什么?
参考答案:
①煤气管道保持正压。②炭化室燃烧室压力接近正常。③停止加热时通知炉上停止出炉。④尽量保持炉温,使炉温下降少,而且下降均匀。
已知Ksp(PbCl2)=1.6×10-5,Ksp(PbI2)=7.1×10-9,Ksp(PbS) =8.0×10-28。若沉淀过程中依次看到白色 PbCl2、黄色PbI2和黑色PbS三种沉淀,则往Pb2+溶液中滴加沉淀剂的次序是 [ ]
A. Na2S、NaI、NaCl
B. NaCl、NaI、Na2S
C. NaCl、Na2S、NaI
D. NaI、NaCl、Na2S
________, his idea was accepted by all the people at the meeting.
A.Strange as might it sound
B.As it might sound strange
C.As strange it might sound
D.Strange as it might sound