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问题 选择题

将a molNa2O2和b mol NaHCO3固体混合后，在密闭容器中加热到250℃，让其充分反应。当排出气体为两种气体时，a : b 的值不可能是

A．1:1

B．1:2

C．2:3

D．3: 2

答案

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题目分析：在250℃时水是气体。发生的反应为2NaHCO3Na2CO3＋CO2↑＋H2O；2Na2O2+2H2O ="4NaOH+" O2↑；2Na2O2+2CO2 =Na2CO3+ O2 。A. 若a : b=1:1，则上述反应恰好完全进行，最后产生的气体为O2。错误。B. 若a : b=1:2，只发生反应2NaHCO3Na2CO3＋CO2↑＋H2O；2Na2O2+2CO2 =Na2CO3+ O2，最后得到的气体为O2和水蒸气。正确 。C．若a : b=2:3，发生反应为2NaHCO3 Na2CO3＋CO2↑＋H2O； 2Na2O2+2CO2 =Na2CO3+ O2 ；2Na2O2+2H2O="4NaOH+" O2↑；第三个反应没有完全进行，还有过量的水蒸气，因此最后得到的气体中含有O2和水蒸气。正确 。D．若a : b= 3: 2>1:1。NaHCO3不足量，Na2O2过量，最后得到的气体中只有O2。错误。2O2和NaHCO3固体混合混合物在加热时的发生化学反应的知识。

单项选择题

心脏骤停一旦确诊，应首先（）

A.清理呼吸道

B.气管内插管

C.人工呼吸

D.口对口呼吸

E.心脏按压
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单项选择题

When something goes wrong, it can be very satisfying to say," Well, it’s so-and-so’s fault. "or "I know I’m late, but it’s not my fault ; the car broke down. "It is probably not your fault, but once you form the habit of blaming somebody or something else for a bad situation, you are a loser. You have no power and could do nothing that helps change the situation. However, you can have great power over what happens to you if you stop focusing on whom to blame and start focusing on how to remedy the situation. This is the winner’s key to success.

Winners are great at overcoming problems. For example, if you were late because your car broke down, maybe you need to have your car examined more regularly. Or, you might start to carry along with you the useful phone numbers, so you could call for help when in need. For another ex-ample, if your colleague causes you problems on the job for lack of responsibility or ability, find ways of dealing with his irresponsibility or inability rather than simply blame the person. Ask to work with a different person, or don’t rely on the person. You should accept that the person. Ask to work with a different person, or don’t rely on this person. You should accept that the person is not reliable and find creative ways to work successfully regardless of how your colleague fails to do his job well.

This is what being a winner is all about—creatively using your skills and talents so that you are successful no matter what happens. Winners don’t have fewer problems in their lives ; they have just as many difficult situations to face as anybody else. They are just better at seeing those problems as challenges and opportunities to develop their own talents. So, stop focusing on "whose fault it is". Once you are confident about your power over bad situations, problems are just stepping stones for success.

The underlined word remedy in Paragraph 1 is closest in meaning to () .

A. avoid

B. accept

C. improve

D. consider
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