【单选题】用已知浓度的盐酸来测定某Na 2 CO 3 溶液的浓度时,若配制Na 2 CO 3 溶液时所用Na 2 CO 3 中分别含有: ①NaOH②NaCl③NaHCO 3 ④K 2 CO 3 杂质,所测结果偏低的是 [ ]
【单选题】In what way armed robberies are Americanized in Britain?
A.
Handguns instead of shotguns are used in armed robberies.
B.
Convenience stores become the targets at night and the criminals are not professional.
C.
British police find it is very difficult to crack the crime as American police.
D.
There is a sharp rise of robberies committed by Americans in Britain.
【单选题】对正在发育的大中型岩堆,线路通过时最好采取的措施是( )。
【简答题】The whole country was armed in a few days.英译汉
【单选题】—How long ________ at this job? —ince 1990.
B.
have you been employed
【单选题】配制 C ( Na 2 CO 3 )= 0.5mol • L -1 溶液 500ml ,应称取 Na 2 CO 3 ( )g 。 M ( Na 2 CO 3 )= 106 g . mol -1 。
【单选题】配制Na2CO3 溶液(0.01mol/L)100ml,已知Na2CO3 分子式 105.99,称取Na2CO3()
【单选题】欲配制c(Na2CO3)=0.5mol/L溶液500mL,应称取Na2CO3()。
【判断题】对正在发育的大中型岩堆,线路通过时最好采取避绕的措施.