问题 多选题

下列实验方案不能达到实验目的是(  )

A.用燃着的木条鉴别氧气和二氧化碳

B.用酚酞试液鉴别稀盐酸和氯化钠溶液

C.用水鉴别碳酸钙粉末和碳酸钠粉末

D.用碳酸钠粉末鉴别稀盐酸和稀硫酸

答案

A、由于氧气能够助燃而二氧化碳不能,所以用燃着的木条鉴别时能够燃烧更旺的是氧气,能使燃着木条熄灭的是二氧化碳;

B、稀盐酸溶液显酸性,氯化钠溶液呈中性,由于酚酞试液遇酸性和中性溶液均不会变色,所以该鉴别方法不可行;

C、碳酸钙不溶于水而碳酸钠能溶于水,所以可以用水鉴别碳酸钙粉末和碳酸钠粉末;

D、碳酸钠与稀盐酸和稀硫酸反应时的现象均是有气泡(二氧化碳)产生,现象相同,所以用碳酸钠粉末鉴别稀盐酸和稀硫酸不可行;

故选BD

填空题
阅读理解

阅读理解

     Every day has just 24 hours - and this applies to all people. Some people are constantly pushed for

time. This article is about how we can learn to manage our valuable time more effectively.

     In reality we cannot manage time. We can only manage ourselves and our relationship with time.   1   

And habits are not that easy to changes.

     Below here are tips that can help you manage your time better.

     Organize your goals.

     Organize your goals based on two criteria: degree of urgency and importance: a. Should be done

today, tomorrow, etc. b. Should be done at "that date". c. Can be put off for so many days. d. Can ask

someone else to do it.    2  

     Clean up your list.

     Make a list of everything you think that is not helping or benefiting you and do not do them!

     Focus on one goal.

     Concentrate only on one goal at a time. Otherwise, if while dealing with something you think about

everything you can do later, most likely you will get bored and disappointed.    3   The boredom (厌倦)

is guaranteed with this way of thinking.

     Identify your deadlines.

        4   Divide the activities per day / week and long-term goals to get a clear

picture of what you have to do and when.

     Find suitable work environment.

        5  

     Be realistic.

     Make sure that your goals are realistic and do not try for the impossible.

     Say "NO".

     Learn to say "no" to other activities, requests and people who eat your time

     (unless indeed at that very moment it is necessary for you to help them).

A. Allow time to adjust your list if necessary.

B. After all, how we use our time is largely a matter of habit.

C. Create a suitable environment to work, one that fits your style.

D. Check the list of what you should do and when it must be completed.

E. After organizing your goals, start with the most important and urgent.

F. It is like every time you eat you think all the meals you must eat in your life.

G. Do not let boredom discourage you if what you have to complete is boring.