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问题 实验题

某二氧化锰样品中含有杂质炭，为测定该样品中二氧化锰的质量分数，某兴趣小组设计了如下实验方案：利用下图实验装，在一定量的样品中通入干燥纯净的氧气，使杂质炭在加热条件下反应生成CO2来进行分析测定。

（1）仪器①的下端插在液面下是为了防止                             ，如果该实验选择甲装置来制取氧气，则反应的化学方程式为                                 。

（2）用乙装置可用来收集和干燥气体。若在烧瓶内装入浓硫酸进行气体干燥，气体应从              端通入（选填“a”或“b”），下列气体中不能用浓硫酸干燥的是                       。

A．H2 B．NH3 C．CO2 D．O2

（3）丙是用干燥纯净的O2与样品反应来测定二氧化锰质量分数的装置，仪器③中装有碱石灰，其作用是___________________________________。

（4）为验证装置丙中②已将CO2吸收完全，可在②与③之间加入丁装置进行证明，则丁装置中加入的试剂为                       

A. 浓盐酸　　B. 澄清石灰水　　C. 烧碱溶液 D. 浓硫酸

（5）称取8g二氧化锰样品进行实验，丙中装置②反应前后的质量差为1.1 g，计算样品中二氧化锰的质量分数为多少？

答案

（1）产生的气体从长颈漏斗逸散到空气中；2H2O22H2O+ O2↑

（2）b；B

（3）吸收空气中的二氧化碳，使实验数据更准确

（4）B

（5）解：设样品中二氧化锰的质量分数为x%。

                C + O2CO2

               12               44 

         8g×(1－x%)      1.1 g 

         12 ：44=［8 g×（1－x%）］：1.1g 

         x%=96.3%

答：样品中二氧化锰的质量分数为96.3%。

选择题

— Does he prefer tea             coffee?    — Tea. [ ]

A. to

B. or

C. and

D. but

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单项选择题

Caesar was right. Thin people need watching. I’’ve been watching them for most of my adult life, and I don’’t like what I see. When these narrow fellows spring at me, I quiver to my toes. Thin people come in all personalities, most of them menacing. You’’ve got your "together" in person, your mechanical thin person, your condescending thin purism, your tsk-tsk thin person, your efficiency-expert thin person. All of them are dangerous.In the first place, thin people aren’’t fun. They don’’t know how to goof off, at least in the best, fat sense of the word. They’’ve always got to be adoing. Give them a coffee break, and they’’ll jog around the block. Supple them with a quiet evening at home, and they’’ll fix the screen door and lick S & H green stamps. They say things like "there aren’’t enough hours in the day". Fat people never say that. Fat people think the day is too damn long already.Thin people make me tired. They’’ve got speedy little metabolisms that cause them to bustle briskly. They’’re forever rubbing their bony hands together and eyeing new problems to "tackle". I like to surround myself with sluggish, inert, easygoing fat people, the kind who believe that if you clean it up today, it’’ll just get dirty again tomorrow.Some people say the business about the jolly fat person is a myth, that all of us chubbies are neurotic, sick, sad people. I disagree. Fat people may not be chortling all day long, but they’’re a hell of a lot nicer than the wizened and shriveled. Thin people turn surly, mean, and hard at a young age because they never learn the value of a hot-fudge sundae for easing tension. Thin people don’’t like gooey soft things because they themselves are neither gooey nor soft. They are crunchy and dull, like carrots. They go straight to the heart of the matter while fat people let things stay all blurry and hazy and vague, the way things actually are. Thin people want to face the truth. Fat people know there is no truth. One of my thin friends is always staring at complex, unsolvable problems and saying, "The key thing is fat people never say that." They know there isn’’t any such thing as the key thing about anything.

When it comes to looking at things, fat people and thin people never come to terms with each other because________.

A．in nature thin people have less sensational inclination than most fat people who are always at the mercy of fat

B．in essence thin people are less emotional and touchy than fat people who are too impulsive

C．in nature thin people look at things in rose-colored spectacles whereas fat people always take a dim view of the objects

D．In essence thin people are too quick on the trigger whereas fat people are slow at picking up subtle things
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