问题 问答题

请根据图示回答下列问题:

(1)写出图中标号的仪器名称:①______,②______

(2)实验室用高锰酸钾制取氧气的化学方程式为:______,可以选用的气体收集装置是(用A、B、C、D、E、F等填空)______;

(3)实验室制取氧气还有另一种方法,其反应原理和高锰酸钾制取氧气的原理不同,所选用的气体发生装置也不相同.这两种制法需选用不同气体发生装置的原因是:______;

(4)装置A和C都可以作为实验室制取某种气体的发生装置,两者相比,A具有的主要优点是:______.

答案

(1)要熟记常见仪器的名称和用途;

(2)高锰酸钾制取氧气的反应物是高锰酸钾,生成物是锰酸钾、二氧化锰、氧气,利用观察法进行配平即可,反应条件是加热;收集方法的选择是根据:难溶于水或不易溶于水用排水法收集,密度比空气大用向上排空气法收集,密度比空气小用向下排空气法收集,氧气密度比空气大,可以用向上排空气法收集,不易溶于水,可以用排水法收集;

(3)过氧化氢溶液和二氧化锰制取氧气反应物的状态是固体和液体,不需要加热,如果固体与固体反应制取气体需要加热例如用高锰酸钾制氧气,所以说与反应物的状态有关;

(4)装置A中是双孔塞,可以随时加入液体药品,装置C是单孔塞,不能随时加入液体药品,加入药品时需要拿下塞子,会混入空气.

故答案为:(1)①长颈漏斗②酒精灯;

(2)2KMnO4

  △  
.
 
K2MnO4+MnO2+O2↑;D、E;

(3)反应物的状态不同,反应条件不同;

(4)可以随时添加液体反应物并且不会混入空气.

多项选择题
单项选择题

Home prices slid in November, raising questions about whether the housing recovery is robust enough to maintain a sustained turnaround. From October to November, home prices fell 0.2% after (1) 0.1% in October, according to a report Tuesday by Standard & Poor’s/Case-Shiller’s home price index. (2) five of the 20 metro areas (3) by the index saw price increases for the month.

On a(n) (4) basis, prices were 5.3% lower in November than in November 2008. Prices were the same as in late 2003. "What we’ve seen (5) the past couple of months is that the pace of (6) has fallen down," says Maureen Maitland of Standard & Poor’s. "Some markets have (7) Is that because we haven’t (8) the foreclosure (回赎权的取消) cycle Because of unemployment We’re not seeing the (9) we were seeing in the last summer months. "

Metro areas that have seen a retreat in home prices (10) Seattle, Charlotte, Las Vegas and Tampa. All four (11) gains they made in recent months (12) . (13) , for the 20-metro index, the annual rate of decline is improving. That (14) , with other recent housing reports that show prices (15) or accelerating, could point to (16) the housing market is starting to (17) its footing, some economists say. Existing home sale prices were $178 300 in December, which is 1.5% higher than December 2008, according to a report this week by the National Association of Realtors. That was the first year-over-year (18) in median price since August 2007.

"The most (19) thing we can say is not only the market is stabilizing, but we’ve seen that housing demand is p," says Bernard Baumohl, with the Economic Outlook Group. "Housing probably will continue to climb upwards through the summer, (20) it could slip a little as the tax credit expires. \

12()

A.deleted

B.validated

C.finished

D.erased