若=4+,则cot(+A)=_____________.
下列关于离子共存的说法不正确的是 A．在溶液中K+、Fe3+、Cl－、S2－是因发生氧
根据下列反应的化学方程式，判断有关物质的还原性强弱顺序，正确的是（ ）I2+SO2+2H2O====H2SO4+2HI2FeCl2+Cl2====2FeCl32FeCl3+2HI====2FeCl2+2HCl+I2A.I-＞Fe2+＞Cl-
In China, if you are not married by the time you are 30, you are in for trouble: social blame and pressure from family and friends can get you down. And if you are a woman, it’s even worse. Many
对按劳分配的分配方式理解不正确的是：（ ） A、这是由我国现实的经济条件决定的 B、社会主义条件下人们劳动的性质和特点，是实行这一分配
2如图是用来表示某物质发生化学变化的微观示意图．图中不同颜色的圆分别表示两种元素的原子，仔细观察下图，回答下列问题： （1）A物质属于 （
某同学组装了如图所示的电化学装置，电极Ⅰ为Al，其他电极均为Cu，则 ( ) A. 电流方向：电极Ⅳ→Ⓐ→电极Ⅰ B. 电极Ⅰ发生还原反应 C. 电
When I was six, Dad brought home a dog one day, who was called “Brownie”, My brothers and I all loved Brownie and did different things with her. One of us would walk her, another would feed her ,t
