【简答题】分光光度法中参比溶液的作用是什么?如何选择适宜的参比溶液?
【单选题】We ___ eighteen lessons by the end of this term.
【简答题】设有下列文法: PROGRAM→begin d;S end S→d;S|sT T→εf;sT (1)试构造该文法的LL(1)分析表。 (2)给出句子begin d;s;s end的分析过程。
【单选题】He picked his cap ______ from the floor and stuck it back on his head.
【单选题】He picked up his cap from the floor and stuck it back on his head.
A.
to take hold of and lift or move
B.
to go somewhere in your car and collect sb. who is waiting for you
C.
to get information or a skill by chance rather than by making a deliberate effort
【简答题】为探究SO 2 与可溶性钡盐能否反应生成白色BaSO 3 沉淀,甲、乙两同学用下图所示装置进行实验(夹持装置、加热装置已略,气密性已检验) 实验操作和现象 (1)A中反应的化学方程式是_________________ 。 (2)C中可溶性钡盐溶液X为_________ 。实验过程中,发现液体Y不能很顺利地滴下,则可如何改进:_________。 (3)分析B中不溶于稀盐酸的沉淀的产生原因,甲同学...
【单选题】Sea levels are______to rise between 7 and 23 inches by the end of 21st century.
【简答题】如何选择使用参比溶液?参比溶液的作用是什么?
【简答题】分光光度法中参比溶液的作用是什么?如何选择适宜的参比溶液?