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问题 多选题

只通过一种试剂，不可以鉴别出来的一组物质是（　　）

A．H2SO4、NaOH、Ca（OH）2、NaCl

B．MgCl2、H2SO4、Na2SO4、HCl

C．K2SO4、NH4NO3、（NH4）2SO4、NaCl

D．MgCl2、Ba（NO3）2、Fe2（SO4）3、CuSO4

答案

A、四种物质中两种碱，一种酸和一种盐，没有一种试剂能将四种溶液鉴别出来．

B、四种物质中两种酸，两种盐，考虑硫酸根可用钡离子，考虑盐酸可用碳酸根离子，若加入碳酸盐，则硫酸、盐酸不能鉴别，加入氯化钡，则硫酸和硫酸钠不能鉴别，故没有一种试剂能将四种溶液鉴别出来．

C、可用氢氧化钡一次鉴别出来，硫酸钾和氢氧化钡反应产生硫酸钡沉淀，硝酸铵和氢氧化钡反应产生氨气，硫酸铵和氢氧化钡反应产生硫酸钡和氨气，氯化钠和氢氧化钡不反应，故可以鉴别．

D、用水作溶剂，硫酸铜溶于水呈蓝色，硫酸铁溶于水呈棕黄色，氯化镁和硝酸钡溶于水无色，将硫酸铜溶液分别加入到两种无色溶液中，产生白色沉淀的是硝酸钡，无现象的是氯化镁．故可以鉴别．

故选AB

选择题

下列关于灭火的方法中，正确的是（　　）

A．扑灭森林火灾，设置隔离带

B．油着火，用水浇灭

C．熄灭酒精灯，用嘴吹灭

D．仓库着火，首先打开门窗通风
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单项选择题

I will never forget the year I was about twelve years old. My mother told us that we would not be (16) Christmas gifts because there was not enough money. I felt sad and thought, "What would I say when the other kids asked what I’ d (17) " Just when I started to (18) that there would not be a Christmas that year, three women (19) at our house with gifts for all of us. For me they brought a doll. I felt such a sense of (20) that I would no longer have to be embarrassed when I returned to school. I wasn’t (21) . Somebody had thought (22) of me to bring me a gift.

Years later, when I stood in the kitchen of my new house, thinking how I wanted to make my (23) Christmas there special and memorable, I (24) remembered the women’s visit. I decided that I wanted to create that same feeling of (25) for as many children as I could possibly reach.

So I (26) a plan and gathered forty people from my company to help. We gathered about 125 orphans (孤儿) at the Christmas party. For every child, we wrapped colorful packages filled with

toys, clothes, and school supplies, (27) with a child’ s name. We wanted all of them to know they were (28) Before I called out their names and handed them their gifts, I (29) them that they couldn’t open their presents (30) every child had come forward. Finally the (31) they had been waiting for came as I called out, "One, two, three. Open your presents!" As the children opened their packages, their faces beamed and their bright smiles (32) up the room. The (33) in the room was obvious, and (34) wasn’ t just about toys. It was a feeling, and the feeling I knew (35) that Christmas so long ago when the women came to visit. I wasn’t forgotten. Somebody thought of me. I matter.

25（）

A.strength 

B.independence 

C.importance 

D.safety
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