题干

化学与生产、生活息息相关.

(1)水是生命之道

自来水是我国目前主要的生活饮用水.下表是我国生活饮用水的部分标准:

项目

标准

感官指标

无异味、异臭

化学指标

pH6.5﹣8.5,游离氯≥0.3mg/L﹣1,铁<0.3mg/L…

①感官指标表现的是自来水的 ____性质(填“物理”或“化学”).

②化学指标中的pH=6.7时,表明自来水呈 ____性;

③生活可用 ____来区别硬水和软水.

④自来水中的游离氯有少量可转变成氯离子,如图为氯原子结构示意图:则氯离子的符号: ____;

(2)分类产生价值,垃圾变成资源

①废旧干电池内部填有氯化铵(NH4Cl)和二氧化锰(MnO2),二氧化锰中锰元素化合价为 ____.

②废旧铝制易拉罐属于 ____(填“金属材料”或“合成材料”),其“不生锈”的原因是铝表面生成一层致密的氧化物薄膜,写出反应的化学方程式 ____.

上一题 下一题 0.0难度 选择题 更新时间:2019-10-22 04:09:08

答案(点此获取答案解析)

物理,酸,肥皂水,Cl﹣,+4,金属材料,4Al+3O2=2Al2O3

同类题4

阅读理解七选五。根据短文内容,从短文后的选项中选出能填入空白处的最佳选项。选项中有两项为多余选项。

Public Speaking Training

·Get a coach

    ____,so get help. Since there are about a billion companies out there all ready to offer you public speaking training and courses, here are some things to look for when deciding the training that's right for you.

·Focus on positives

    Any training you do to become more effective at public speaking should always focus on the positive aspects of what you already do well. Nothing can hurt confidence more than being told that you aren't doing well. ____, so good public speaking training should develop those instead of telling you what you shouldn't do.

·____    If you find a public speaking course that looks as though it's going to give you lots of dos and don'ts, walk away! Your brain is so full of what you're going to be talking about.

    ____ As far as we're concerned, there are basically no hard and fast rules about public speaking. Your audience can be your friends.

·You are a special person not a clone

    Most importantly, good public speaking training should treat you as a special one, with your own personal habits. ____ Your training course should help you bring out your personality, not try to turn you into someone you're not.

A. You aren't like anybody else

B. You already do lots of things well

C. Turn your back on too many rules

D. Check the rules about dos and don'ts

E. Whatever the presentation, public speaking is tough

F.The one thing you don't want is for them to fall asleep

G. So trying to force a whole set of rules into it will just make things worse