问题 实验题

某兴趣小组发现一袋腌制松花蛋的泥料,配料表上的成分是氧化钙、纯碱和食盐。他们要探究在腌制松花蛋过程中都有哪些物质对鸭蛋起作用。于是取少量泥料在水中溶解,充分搅拌后过滤,取滤液探究其成分。

【猜想与假设】他们都认为滤液中一定有NaCl和NaOH。生成氢氧化钠的化学方程式为____________。对其他成分他们分别做出了如下猜想:

小亮猜想:还可能有Na2CO3

小强猜想:还可能有Ca(OH)2和Na2CO3

你认为谁的猜想是错误的____,理由是________________。你还能做出的猜想是:还可能有________。

【活动与探究】小亮取一定量的滤液于试管中,向其中滴加了几滴稀盐酸,振荡,没有气泡,于是他得出结论:没有Na2CO3。请你选择CO2以外的物质,设计一个实验方案验证你的猜想。

【反思】小强认为小亮的结论不严密,理由是________________。

答案

【猜想与假设】Na2CO3+Ca(OH)2==CaCO3↓+2NaOH;小强;Na2CO3和Ca(OH)2不能共存;Ca(OH)2

【活动与探究】取少量滤液于试管中,向其中加入碳酸钠溶液;若产生白色沉淀,则证明滤液中有Ca(OH)2,若不产生白色沉淀,则证明滤液中没有Ca(OH)2(其他合理答案也可)。

【反思】滴加盐酸量很少,在氢氧化钠未反应完之前,不会产生气泡。

不定项选择
单项选择题

Are you one of those who always fear whenever a dog is approaching If you are, you have got phobia ( a very p feeling of being afraid of something ). Of all human fears, phobias may be the most uncontrollable. They are most often caused by a particular situation or object. In general, pho- bias can mainly be divided into three varieties. To begin with, agoraphobia is a fear of staying in strange surroundings, for example, an unfamiliar place, or an open area. Social phobia refers to the anxiety people show when they have to stay or perform on social events, for instance, speaking in front of the class. Lastly, there are a wide range of specific phobias. People suffering from this kind of phobia are terrified of specific objects or creatures, such as spiders, perhaps to your surprise, clowns. Besides, there are about six hundred and fifty phobias listed by psychologists (心理学家) as yet.
Faced with their phobias, many people choose to do nothing but just escape the situations or objects they fear. Psychologists, however, warn that if not treated properly, this kind of anxiety will get worse, so that it may disturb the sleep pattern, cause physical symptoms, and finally affect their daily activities. As for treatment, clinical research has discovered that medicine for anxiety is not successful in curing phobias. However, the anxiety disorders can be efficiently treated through cognitive behavioral therapy (认知行为疗法) , through which patients are led to inspect the connections between their own fear and the situation or object, and then actively choose the acceptable treatments. Also, other treatments proved effective in reducing phobias are meditation, listening to calming music, and so on.

What do those with agoraphobia feel terrified of and anxious about

A.Staying on a square.

B.Touching insects, like spiders.

C.Being harmed by viruses.

D.Giving a speech in presence of many peopl