问题
选择题
____ you bring _____ to his attention that now students are bearing too heavy a leaming load(负担) ? [ ]
A. Why not; that
B. Why not; this
C. Why don't; it
D. Why don't; what
答案
答案:C
____ you bring _____ to his attention that now students are bearing too heavy a leaming load(负担) ? [ ]
A. Why not; that
B. Why not; this
C. Why don't; it
D. Why don't; what
答案:C
(8分)如何用所提供的试剂和方法除去混合物中的杂质(括号内为杂质)。将所选答案的编号填入表内相应的空格中(不需要外加试剂的,此格可标“——”,可重复选择)
I.可供选择的试剂:
A.盐酸
B.NaOH溶液
C.CuO
D.饱和的NaHSO3溶液II.可供选用的操作:①洗气 ②加热 ③过滤 ④分液
混合物 | 所用试剂 | 主要操作 | |
(1) | BaSO4(I2) | ||
(2) | CaCO3(SiO2) | ||
(3) | SO2(HCl) | ||
(4) | CO2(CO) |