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问题 选择题

25°C时某些弱酸的电离平衡常数如下表，下列说法正确的是( )

化学式CH3COOHHClOH2CO3
KaKa=1.8×10-5Ka=3.0×10-8Ka1=4.1×10-7

Ka2=5.6×10-11

 

A．等物质的量浓度溶液酸性由强到弱的顺序为：H2CO3＞CH3COOH＞HClO

B．等物质的量浓度溶液pH由大到小的顺序为：Na2 CO3＞NaClO＞NaHCO3＞CH3COONa

C．等物质的量浓度的NaClO和NaHCO3 混合溶液中：c(HClO)＋c(ClO－)＝c(HCO3－)＋c(CO32－)＋c(H2CO3)

D．向次氯酸钠溶液中通入少量二氧化碳气体的离子方程式为：ClO—+CO2+H2O=CO32—+2HClO

答案

BC

题目分析：相同温度下，根据表格中给出的3种弱酸的电离常数进行比较，可知相同条件下酸性强弱顺序为CH3COOH＞H2CO3＞HClO，A错误；其对应的强碱盐水解呈碱性，根据越弱越水解规律可知，相同条件下水解程度Na2 CO3＞NaClO＞NaHCO3＞CH3COONa，所以B正确；根据物料守恒，等物质的量浓度的NaClO和NaHCO3 混合溶液中c(HClO)＋c(ClO－)＝c(HCO3－)＋c(CO32－)＋c(H2CO3)，C正确；因为碳酸酸性强于次氯酸，而HCO3-酸性弱于次氯酸，所以根据强酸值弱酸原理，向次氯酸钠溶液中通入少量二氧化碳气体的离子方程式为：ClO—+CO2+H2O=HCO3—+HClO，D错误；故选BC。

完形填空

阅读下面短文, 掌握其大意, 然后从1—10各题所给的A、B、C和D项中, 选出最佳选项, 并在答题卡上将该项涂黑。
Philo Farnsworth, the inventor of one of the country’s greatest machines was actually born in a log cabin,  1 to high school on horse back and without   2 of university degree（indeed, at age 14）, thought of the idea of electronic television. In 1906 Farnsworth was born in a community near Beaver City, Utah,  3 by his grandfather.  4 he was 12, his family moved to a ranch （大牧场）in Rigby, Idaho, which was four miles from, the nearest high school,  5 necessitating（使成为必要）his daily horseback rides. Because he was interested in the electron and electricity, he persuaded his chemistry teacher, Justin Tolman, to give him   6 instruction and to allow him to listen to a senior course.
The death of his father forced him to leave at the end of his second year, but, as it   7 , at no great intellectual cost. There were, at the time, no more than a handful of men   8 the planet who could have understood Farnsworth’s idea for building an electronic television system, and it’s   9 that any of them were at this local community. One such man was Vladimir Zworykin who had moved to the US from Russia with a Ph. D in electrical engineering. He went to work for Westinghouse with a dream of building an all-electronic television system. But he wasn’t   10 to do so.
小题1:
A．rodeB．ranC．droveD．jumped
小题2:

2,4,6

 
A．sakeB．applicationC．benefitD．significance

小题3:
A．livedB．settledC．inheritedD．occupied
小题4:
A．BecauseB．WhenC．HoweverD．Until
小题5:
A．thusB．thenC．finallyD．yet
小题6:
A．importantB．interestingC．specialD．vivid
小题7:
A．turned outB．showed upC．bore outD．reflected on
小题8:
A．inB．withinC．aroundD．on
小题9:
A．necessarilyB．essentialC．falseD．unlikely
小题10:
A．possibleB．capableC．thoughtfulD．able
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名词解释

6sigma
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