试题与答案

在元素周期表中,同一主族元素化学性质相似。目前也发现有些元素的化学性质和它在周期

题型:填空题

题目:

在元素周期表中,同一主族元素化学性质相似。目前也发现有些元素的化学性质和它在周期表中左上方或右下方的另一主族的元素性质相似,称为对角线规则。据此回答:

(1).锂在空气中燃烧,除生成_______外,也生成微量的_________(用化学式做答)。

(2).铍的最高价氧化物对应的水化物的化学式是__________,它属于两性氧化物,可以证明这一结论的离子方程式是 ____________________;_________________________。

(3).已知反应 Be2C + 4H2O = 2Be(OH)2 + CH4↑,则Al4C3遇足量强碱溶液反应的离子方程式为_______。

(4).科学家证实,BeCl2属于共价化合物,设计一个简单实验证明这一点,你想到的可行的方法是_________________________________。

答案:

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参考答案:B

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题型:单项选择题

The "Karat" marking on jewelry tells you what proportion of gold is mixed with other metals, ff 14 parts of gold are mixed with 10 parts of base metal, the combination is called 14-Karat (14K) gold. The higher the Karat rating, the higher the proportion of gold in the object. The lowest Karat gold that can be marketed in the United States is 10-Karat gold. Jewelry does not have to be marked with its Karat quality, but most of it is. ff there is a Karat quality mark, next to it must be the U.S. registered trademark of the person or company that will stand behind the mark, as required by the National Gold and Silver Stamping Act.

If a ring is stamped 24K, it has

A.204 parts of gold,

B.24 parts of gold.

C.two and four-tenths parts of gold.

D.10 parts of gold.

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