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问题 选择题

把0.05mol醋酸分别加入到下列100mL溶液中，溶液的导电能力变化最明显的（　　）

A．0.5mol/LNaOH溶液

B．0.5mol/L盐酸

C．0.5mol/LNH4Cl溶液

D．0.5mol/L氨水

答案

A、100mL0.5mol/LNaOH溶液中加入0.05mol醋酸，得到100mL0.5mol/LNaAc溶液，离子浓度变化基本不变，则溶液的导电性不变，故A不选；

B、100mL0.5mol/L的盐酸溶液中加入0.05mol醋酸，得到100mL0.5mol/LHCl和0.5mol/L的醋酸溶液，但盐酸电离生成的氢离子抑制醋酸电离，离子的浓度比原来的大些，导电性比原来的强，故B不选；

C、100mL0.5mol/LNH4Cl溶液中加入0.05mol醋酸，得到100mL0.5mol/LNH4Cl和0.5mol/L的醋酸溶液，但NH4Cl电离生成的铵根离子抑制醋酸电离，离子的浓度比原来的大些，导电性比原来的强，故C不选；

D、因0.5mol/L氨水中存在电离平衡，电离的程度很弱，溶液中的离子浓度很小，导电性差，但0.05mol醋酸加入到100mL0.5mol/L氨水溶液中得到100mL0.5mol/LNH4Ac溶液，NH4Ac是强电解质，在水中完全电离，则离子浓度增大明显，导电性变化明显，故D选；

故选D．

单项选择题 A1/A2型题

肾上腺皮质的球状带（）

A.分泌糖皮质激素

B.分泌盐皮质激素

C.位于皮质最浅层

D.在皮质三个带中最薄

E.细胞排列成环形或半环形
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单项选择题

Generally speaking, a British is widely regarded as a quiet, shy and conservative person who is (1) only among those with whom he is acquainted. When a stranger is at present, he often seems nervous, (2) embarrassed. You have to take a commuter train any morning or evening to (3) the truth of this. Serious-looking businessmen and women sit reading their newspapers or dozing in a corner; hardly anybody talks, since to do so would be considered quite offensive. (4) , there is an unwritten but clearly understood code of behavior which, (5) broken, makes the offender immediately the object of (6) .

It has been known as a fact that a British has a (7) for the discussion of their weather and that, if given a chance, he will talk about it (8) . Some people argue that it is because the British weather seldom (9) forecast and hence becomes a source of interest and (10) to everyone. This may be so. (11) a British cannot have much (12) in the weathermen, who, after promising fine, sunny weather for the following day, are often proved wrong (13) a cloud over the Atlantic brings rainy weather to all districts! The man in the street seems to be as accurate — or as inaccurate — as the weathermen in his (14) .

Foreigners may be surprised at the number of references (15) weather that the British make to each other in the course of a single day. Very often conversational greetings are (16) by comments on the weather. "Nice day, isn’t it" "Beautiful!" may well be heard instead of "Good morning, how are you" (17) the foreigner may consider this exaggerated and comic, it is worthwhile pointing out that it could be used to his advantage. (18) he wants to start a conversation with a British but is (19) to know where to begin, he could do well to mention the state of the weather. It is a safe subject which will (20) an answer from even the most reserved of the British.

18（）

A. Even if

B. Because

C. If

D. For
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