问题 问答题

已知在化工生产中,原料往往不能全部转化成产品.某化工厂常用电解纯净的饱和食盐水的方法来得到烧碱溶液,再经浓缩、蒸发等步骤制造固体烧碱.某化学兴趣小组要分析该化工厂仓库里的固体烧碱样品.

(1)小组成员猜测该样品中含有碳酸钠,支持这种猜测的依据是(用化学方方程式表示)______.小组成员选用了三种不同类别的试剂,进行实验,验证猜想,并得出结论��碳酸钠确实存在.请你将实验过程中涉及的化学方程式填在下表中.

化学方程式
试剂1
试剂2
试剂3
(2)请你也猜测一下,该样品还可能含有______杂质.设计一个实验方案,来证实你的猜测是正确的.

实验步骤实验现象
(1)把固体烧碱溶于水
(2)

答案

(1)仓库中的氢氧化钠可能会吸收空气中的二氧化碳,并且反应生成碳酸钠,反应的化学方程式为:CO2+2NaOH=Na2CO3+H2O.

故填:CO2+2NaOH=Na2CO3+H2O.

碳酸钠能和氯化钙反应生成碳酸钙沉淀和氯化钠,能和氢氧化钙反应生成碳酸钙沉淀和氢氧化钠,能和稀盐酸反应生成氯化钠、水和二氧化碳,化学方程式如表中所示:

化学方程式
试剂1CaCl2+Na2CO3═CaCO3↓+2NaCl   
试剂2Na2CO3+Ca(OH)2═CaC03↓+2NaOH
试剂3HCl+NaOH=NaCl+H2O,Na2CO3+2HCl=2NaCl+H2O+CO2
(2)如果氯化钠没有完全电解,那么得到的氢氧化钠中会含有氯化钠.

故填:氯化钠.

可以用硝酸银和稀硝酸来检验氢氧化钠中含有氯化钠,实验步骤、实验现象如表中所示:

实验步骤实验现象
(1)把固体烧碱溶于水固体全部溶解
(2)取少量溶液,先加过量稀硝酸,再滴入硝酸银溶液先有气体逸出,后有白色沉淀生成

单项选择题
阅读理解

阅读下面短文,从A、B、C、D四个选项中选出最佳选项,并在机读卡上相应番号处将该项涂黑。

People who show confidence really seem to have it made. They seize more rewarding careers, keep good relationships, and just seem to do everything with more styles than the rest of us.

So what is the secret? There isn’t one. Self-confidence is a skill and habit that anyone can learn to develop. And although people who are raised in an encouraging environment with confident role models have a hard start in self-confidence development, we all can learn to become more confident at any age.

Try these simple tips for practicing and increasing your self-confidence levels:

Dare to fail. Anybody who’s out there bravely performing is going to fail repeatedly. If you are not failing, you are not trying. So don’t take failure too hard or too personally. Just learn to deal with it and use its lessons to keep improving.

When in doubt, pretend you know what you are doing. Because, if you are confident of your abilities, by the time you have done it, you will be experienced.

Dress for success. You don’t have to be beautiful to be confident. Make the most of your own unique physical characters and weaken your disadvantages.

Listen to yourself. You are the only person who knows what’s right for you. Don’t put others’ opinions above your own inner voice.

Build a confident vocabulary. Stop putting yourself down and give up continually blaming your tiny weaknesses. Learn to show up your strong points and the world will learn to see and celebrate them with you.

Pass on the praise. Praise others for their virtues and strengths. This practice will not decrease your confidence, but help increase it.

小题1: The passage is written mainly __________.

A.to explain the definition of self-confidence

B.to explain the secret of self-confidence

C.to tell people how important self-confidence is

D.to tell people how to build self-confidence小题2:The underlined word “one” in the second paragraph refers to __________.

A.the secret of self-confidence

B.the skill of self-confidence

C.the style of doing things

D.a rewarding career小题3:The main idea of the sixth paragraph is __________.

A.to be confident means to have no disadvantages

B.taking full advantage of your physical characters will help you be confident

C.your unique characters will help you be confident and be successful

D.to be confident means to be beautiful小题4:All the following are tips to increase your self-confidence level EXCEPT_________.

A.not to be afraid of failure

B.dress yourself properly

C.pretend to know everything

D.make your advantages more obvious小题5:__________ will weaken your self-confidence.

A.Praising others for their strong points

B.Always following others’ advice to do things

C.Giving up blaming your weaknesses

D.Believing in yourself