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问题 填空题

短周期元素X、Y、Z、L、M、Q的原子半径和主要化合价见下表

元素代号XYZLMQ
原子半径/nm0．1600．1430．1020．0990．0770．074
主要化合价+2+3+6、-2+7、-1+4、-4-2
 

就以上6种元素，用化学用语回答下列问题

（1）同主族的元素是                ，

（2）写出同周期元素间形成的常温下是有毒气体化合物的分子式为         ，

（3）写出不同周期的元素间形成的常温下为液体且难溶于水的任意一种化合物的电子式         。

（4）等质量的X、Y的单质与足量盐酸反应，生成H2的物质的量之比为      

（5）写出由表中元素形成的物质间发生常见的置换反应的化学方程式            

答案

（1）S  O  (不分先后)（2分）

（2） CO （2分）

（3）或                          （2分）

（4）3：4  （2分）

（5）2Mg+ CO2 2MgO + C  （2分）

题目分析：根据元素原子的半径和主要化合价可判断，X是Mg，Y是Al，Z是S，L是Cl，M是C，Q是O。

（1）同主族的元素是S，O ；

（2）同周期元素间形成的常温下是有毒气体化合物的分子式为CO；

（3）不同周期的元素间形成的常温下为液体且难溶于水的化合物要么是CCl4，要么是CS2，电子式或  ；

（4）等质量的Mg、Al的单质与足量盐酸反应，

Mg   ~    H2                            2Al   ~    3H2

24g        1mol                        2×27g       3mol

1g         xmol                          1g         ymol

生成H2的物质的量之比为x：y＝3：4；

（5）表中元素形成的物质间发生常见的置换反应的化学方程式 2Mg+ CO2 2MgO + C，2H2S+O22H2O+2S，H2S+Cl2=2HCl+S↓。

单项选择题

预算单价法编制施工图预算的基本步骤中，措施费应在( )时计算。

A．套单价
B．工料分析
C．按费用定额取费
D．计算主材费
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单项选择题

The following two questions refer to the following passage:

A prestigious private high school has made available to local families a tuition prepayment plan to ease the burden of paying the school’s hefty tuition when a student matriculates. The plan allows parents of children under three years old to reserve a spot for their child at the school by making a payment of one-fourth of the current annual tuition for the high school. The parents then make an identical payment every year for the next 15 years, and the student’s full four-year tuition is considered paid in full, regardless of how much the regular tuition payments have risen in the intervening years.

Under which of the following circumstances would it be advisable for parents to take part in the prepayment plan ？（）

A. If the school assures parents that participation in the prepayment plan will be taken into consideration when the school admissions council makes decisions about which first-year students to admit to the school

B. If the parents are certain that their child will attend this high school, and if the rate of tuition increase would surpass the rate of return that the parents could earn if they invested the same 16 payments in interest-bearing investments of their own choosing

C. If the children of other parents who have taken part in the prepayment plan have been successful at the high school and gone on to enroll at Ivy League universities

D. If the parents feel that this high school will provide the best educational, athletic, and social experience that their child could receive

E. If the school can guarantee that its level of prestige at the time of the student’s matriculation will be as great as or greater than its current level
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