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问题 选择题

下列各组反应（表内物质均为反应物）刚开始时，放出H2的速率最大的是（　　）

编号金属（粉末状）物质的量酸的浓度酸的体积反应温度
AMg0.1mol6mol/L硝酸10mL60℃
BMg0.1mol3mol/L盐酸10mL30℃
CFe0.1mol3mol/L盐酸10mL60℃
DMg0.1mol3mol/L盐酸10mL60℃

A．A

B．B

C．C

D．D

答案

硝酸和镁反应不生成氢气，所以排除．镁的金属性比铁的强，所以在外界条件相同的情况下，镁比铁的反应速率快；在金属、酸相同的条件下，温度越高、酸的浓度越大，化学反应速率越快，故选D．

单项选择题

CD光盘记录信息的轨迹叫光道，信息存储在______的光道上。

A．一条圆形

B．多条同心环形

C．一条渐开的螺旋形

D．多条螺旋形
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单项选择题

In every cultivated language there are two great classes of words which, taken together, comprises the whole vocabulary. First, there are those words (1) which we become acquainted in daily conversation, which we (2) , that is to say, from the (3) of our own family and from our familiar associates, and (4) we should know and use (5) we could not read or write. They (6) the common things of life, and are the stock in trade of all who (7) the language. Such words may be called "popular", since they belong to the people (8) and are not the exclusive (9) of a limited class.

On the other hand, our language (10) a multitude of words which are comparatively (11) used in ordinary conversation. Their meanings are known to every educated person, but there is little (12) to use them at home or in the market-place. Our (13) acquaintance with them comes not from our mother’s (14) or from the talk of our school-mates, (15) from books that we read, lectures that we (16) , or the more (17) conversation of highly educated speakers who are discussing some particular (18) in a style appropriately elevated above the habitual (19) of everyday life. Such words are called "learned", and the (20) between them and the "popular" words is of great importance to a right understanding of linguistic process.

8（）

A. in public

B.at most

C. at large

D. at best
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