问题 填空题

(14分)我国制碱工业的先驱侯德榜先生,1939年发明了著名的侯氏制碱法,其核心反应原理可用如下化学方程式表示:

NH3+CO2+NaCl+H2O=NH4Cl+NaHCO3(晶体)

依据此原理,欲制得碳酸氢钠晶体,某校学生设计了如下实验装置,其中B装置中的试管内是溶有氨和氯化钠的溶液,且二者均已达到饱和。

(1)A装置中所发生反应的离子方程式为                        

C装置中稀硫酸的作用为                        

(2)下表中所列出的是相关物质在不同温度下的溶解度数据(g/100g水)

参照表中数据,请分析B装置中使用冰水的目的是                       

(3)该校学生在检查完此套装置气密性后进行实验,结果没有得到碳酸氢钠晶体,指导教师指出应在

               装置之间(填写字母)连接一个盛有          的洗气装置,其作用是                     

(4)若该校学生进行实验时,所用饱和食盐水中含NaCl的质量为5.85g,实验后得到干燥的NaHCO3晶体的质量为5.04g,则NaHCO3的产率为      

答案

(1)CaCO3+2H+=Ca2++CO2↑+H2O  吸收从B装置中的试管内逸出的氨气,减少对环境的污染

(2)温度越低,碳酸氢钠的溶解度越小,便于析出

(3)A与B     饱和NaHCO3溶液(其他合理答案均给分)      

除去CO2中混合的HCl气体

(4)60%

题目分析:(1)根据题目的方程式,缺少反应物二氧化碳,所以A装置中是来制取二氧化碳的,写出方程式即可以拆开来形成离子方程式。反应物中有氨气,稀硫酸的作用是吸收未参与反应逸出的氨气。(2)观察表中,发现低温下碳酸氢钠的溶解度很低,所以冰水的作用是为了使碳酸氢钠结晶。(3)没有得到碳酸氢钠的原因可能是因为盐酸挥发出来到了B装置中,与碳酸氢钠反应。所以应该在A和B之间放置一组出去二氧化碳中盐酸的装置。考虑到二氧化碳的存在,放置饱和碳酸氢钠溶液比较合适。(4)反应物氯化钠为0.1mol,能生成的碳酸氢钠理论产量应该有0.1mol,所以产率=0.06/0.1=60%。

点评:本题以侯氏制碱法为背景,综合了很多基础知识,已经实验装置的评价,考察点难度不高,属于简单题。

单项选择题
单项选择题

"What does the middleman do but add to the price of goods in the shops " Such remarks are aimed at the intermediate operations between manufacturers and final customers. This practice usually attracts a lot of attention from the public and the press and the operation most talked about is what is often called wholesaling.The wholesaler buys goods in large quantities from the manufacturers and sells them in smaller parcels to retailers, and for this service his selling price to the retailer is raised several percent higher. But his job is made more difficult by retail demand not necessarily running level with manufacturers’’ production. Because he adjusts or regulates the flow of goods by holding stock until required, he frees the manufacturer, to some extent, from the effect on production of changing demand and having to bear the whole risk.The manufacturer can then keep up a steady production flow, and the retailer has no need to hold heavy stocks, who can call on the wholesaler for supplies any time. This wholesale function is like that of a valve in a water pipe. The middleman also bears part of the risk that would otherwise fall on the manufacturer and also the retailer.The wholesaler provides a purely commercial service, for which he is too well rewarded. But the point that is missed by many people is that the wholesaler is not just someone adding to the cost of goods. It is true one could eliminate the wholesaler but one would still be left with his function: that of making sure that goods find their way to the people who want them.

Which of the following statements is true

A.People cannot do without the wholesaler’s function.

B.The function of the wholesaler does not add to the cost of goods.

C.The wholesaler helps to reduce the price of goods in shops.

D.The wholesaler is well paid for his commercial service.