问题 单项选择题

Questions from 36 to 40 are based on the following passage: Generally, cargo is carried in containers, but sometimes it is still shipped as breakbulk cargo. During the voyage, goods may be stacked on top of or come into violent contact with other goods. And the cargo might be dragged, pushed, rolled, or dropped during unloading, while moving through customs, or in transit to the final destination.Moisture is a constant concern because condensation may develop in the hold of a ship even if it is equipped with air conditioning and a dehumidifier(除湿机). Another aspect of this problem is that cargo may also be unloaded in precipitation, or the foreign port may not have covered storage facilities. Buyers are often familiar with the port systems overseas, so they will often specify packaging requirements. If the buyer does not specify this, be sure the goods are prepared using these guidelines:Pack in p containers, adequately sealed and filled when possible.To provide proper bracing in the container, regardless of size, make sure the weight is evenly distributed.Goods should be palletized when possible containerized.Packages and packing filler should be made of moisture-resistant material.To avoid pilferage, avoid writing contents or brand names on packages. Other safeguards include using straps, seals, and shrink wrapping.Observe any product-specific hazardous materials packing requirements.Normally, air shipments require less heavy packing than ocean shipments, though they should still be adequately protected, especially if they are highly pilferable.Finally, because transportation costs are determined by volume and weight, specially reinforced and lightweight packing materials have been developed for exporting. Packing goods to minimize volume and weight while reinforcing them may save money, as well as ensure that the goods are properly packed.

The packing of cargo delivered by air freight can be().

A.slighter than that of the freight carried by sea

B.heavier than that of the freight carried by sea

C.more pilferable

D.more protective

答案

参考答案:A

实验题

(11分)实验室有一瓶保管不当的试剂(如图),其残缺的标签中只剩下“Na”和“10%”字样。已知它是无色液体,是初中化学常用的试剂。小强和小华很感兴趣,决定对其成分进行探究。

[提出问题]这瓶试剂可能是什么溶液呢?

[交流讨论]根据受损标签的情况判断,这瓶试剂不可能是__________。

A. 酸                          B. 碱                           C. 盐

[查阅资料]

Ⅰ. 初中化学常见的含钠化合物有NaCl、NaOH、Na2CO3、NaHCO3

Ⅱ. Na2CO3和NaHCO3溶液都呈碱性。

Ⅲ. 测定室温(20℃)时,4种物质的溶解度的数据如下表所示。

物质NaClNaOHNa2CO3NaHCO3
溶解度g361092159.6
 

[得出结论]小华根据试剂瓶标注的溶质质量分数10%和上表中的溶解度的数据判断,这瓶试剂不可能是_________。

[作出猜想]①可能是________溶液;②可能是Na2CO3溶液;③可能是NaCl。

[设计并实验]

(1)小强用洁净的玻璃棒蘸取该溶液滴在pH试纸上,测得pH>7,这瓶试剂不可能是__________。

(2)小强为了检验该溶液是NaOH溶液还是Na2CO3溶液,他又进行了如下表所示实验:

[探究实验]

操作步骤实验现象结论及化学方程式
取样于试管中,滴加_____产生大量的气泡猜想②正确
 

把产生的气体通入    

 

 

        

相关的化学方程式是: 

          

[拓展与应用]请你选择与小强不同的试剂,来鉴别NaOH溶液和Na2CO3溶液,你选择__________溶液。

单项选择题