【简答题】Directions: There are 2 passages in this section, Each passage is followed by some questions or unfinished statements. For each of them there are four choices marked A), B), C)and D).You should decide...
【单选题】l-丁醇和乙酸在浓硫酸作用下,通过酯化反应制得乙酸丁酯,反应温度为ll5~l25℃,反应装置如图.下列对该实验的描述错误的是( )
【单选题】计算机当前的应用领域广泛,但据统计其最广泛的领域是
【简答题】实验室用过氧化氢( H 2 O 2 )制取氧气时常用二氧化锰作催化剂.反应的化学方程式2H 2 O 2 Mn O 2 . 2H 2 O+O 2 ↑.有同学提出硫酸铜能否代替二氧化锰作该反应的催化剂.下面请你一起参与实验探究,并回答问题: (1)作出假设:硫酸铜可以作过氧化氢分解反应的催化剂. (2)实验探究: 实验1:取甲、乙两支试管,分别加人等体积的5%过氧化氢溶液.在甲试管中加人适量的硫酸铜溶...
【简答题】In Passage 2, the speaker uses an
example of figure skaters to illustrate the idea that “you can never progress
by never failing”. You are going to give a presentation on this topic. In your
presentat...
【单选题】禽流感是A型禽流感病毒所引起的,是一种急性高度致死性传染病。防治禽流感时需要大量使用过氧乙酸、含氯类消毒剂等。氯胺是一种长效缓释有机氯消毒剂,它与水可以发生复分解反应。其生成物的杀菌能力是一般含氯消毒剂的4~5倍,有关氯胺(NH 2 Cl,分子中Cl的化合价为+1价)的说法不正确的是
A.
氯胺与水发生复分解的产物为NH 2 OH和HCl
【简答题】Academic success (1) in many forms.
【简答题】In the United States, the best-known program designed to promote future academic success is Head Start. The program, which stresses parental involvement, was designed to serve the “whole child”, inclu...
【单选题】维果茨基指出心理机能是由低级向高级发展的原因,下列哪项不是()
A.
起源于社会文化历史的发展,是受社会规律制约的
C.
从个体发展来看,儿童在与成人交往过程中通过掌握高级的心理机能