问题 填空题

某学习小组做以下实验:在溴水中加入足量乙醛溶液,充分反应,溴水褪色;为探究褪色的原因,他们提出了如下猜想:

①溴水中的Br2可能与乙醛发生取代反应,产生HBr;

②乙醛分子中含有不饱和键,溴水可能与乙醛发生加成反应;

③乙醛具有还原性,溴水可能将乙醛氧化为乙酸,Br2转化为HBr.

设计如下方案进行探究:

方案(一):检验褪色后溶液的酸碱性,确定其发生哪类反应;

方案(二):测定反应前溴水中Br2的物质的量和反应后 Br-的物质的量确定其发生哪类反应;

(1)假设测得反应前溴水中Br2的物质的量为a mol,

若测得反应后n(Br-)=0mol,说明溴水与乙醛发生了______反应;

若测得反应后n(Br-)=a mol,说明溴水与乙醛发生了______反应;

若测得反应后n(Br-)=2a mol,说明溴水与乙醛发生了______反应.

(2)向含Br2 0.005mol的溴水中加入足量乙醛使其褪色,然后加过量的AgNO3溶液,过滤、洗涤、干燥、称量,得到固体1.88g.已知CH3COOAg易溶于水,通过计算,判断溴水与乙醛发生的反应为______(填序号):①氧化反应       ②取代反应      ③加成反应

(3)方案(一)是否可行?______ (填“是”或“否”),原因是:______.

答案

(1)如果发生加成反应,则溶液中不存在Br-,如发生取代反应,则amolBr2取代amolH,溶液中应有amolBr-,如发生氧化反应,存在CH3CHO+Br2+H2O=CH3COOH+2H++2Br-,溶液中存在2amolBr-

故答案为:加成;取代;氧化;

(2)得到固体1.88g为AgBr的质量,n(AgBr)=

1.88g
188g/mol
=0.01mol,n(Br-)=2n(Br2),则反应应为氧化反应,

故答案为:①;

(3)方案一中,无论取代(生成HBr)或氧化乙醛(生成CH3COOH),均使反应后溶液显酸性,故不可行,

故答案为:否;因为如果发生的是取代反应,也生成HBr使溶液显酸性.

单项选择题
填空题

Your heart suddenly starts pounding so hard you think it’s going to leap right out of your chest. You’re sweating even though it’s cold out. You feel unsteady on your feet and generally shaky, like the world around you is spinning out of control and you can’t get a grip. Your hands and feet are numb and useless. You’re gasping for breath and feel like you’re drowning.

(41)__________Genetics may be part of the explanation; women are more prone to anxiety or depression, and a history of these mood disorders makes you more likely to have a panic attack. But unhappy life experiences may also increase women’s vulnerability.

A particularly active area of research at the moment is the effect of hormones. Women seem most susceptible to panic attacks during times of hormonal changes, such as adolescence, pregnancy, and so on. Dr. Lilian Gonsalves, psychology at the Cleveland Clinic, says some scientists think that hormonal fluctuation may upset the balance of chemicals in the brain that modulate fear and anxiety, triggering a panic attack. It feels like the fight-or-flight response gone wild with no provocation. (42)__________

Fear of another attack often makes people avoid places where an attack took place, and a small percentage of sufferers may eventually become housebound, a condition called agoraphobia. (43)__________ "We used to say that you don’t die of a panic attack, but I’ve stopped saying that," says Gonsalves. "It could be that during a panic attack you get coronary spasms or an irregular heart rate. "

(44)__________There’s no single cure that works for everyone, but generally, patients use medication, cognitive behavioral therapy or some combination of the two. Cognitive behavioral therapy teaches you a range of techniques—such as relaxation exercises—to deal with everyday anxiety and stress, lessening the chances of another attack. Many people find that drugs help control the problem until they can find a behavioral therapy that works, after which drugs may no longer be necessary. Research has also shown that regular exercise.and activities such as yoga may reduce the severity and number of attacks.

(45)__________If there is nothing wrong, then your doctor will probably refer you to a psychiatrist or psychologist who can work with you on the problem over what may be a period of several months.

It takes a while to feel completely better; generally, antidepressants start working in six to eight weeks, Gonsalves says. But many patients begin to get some relief in just two weeks, she adds. In all, about 80 percent of patients will do well. In the case of the other 20 percent, who don’t respond to treatment, doctors often find that they have missed an underlying medical condition that is behind the attacks.

[A] Suffering from frequent panic attacks also means you are at higher risk of depression, substance abuse and suicide. Some research also indicates that women who have repeated attacks are at higher risk of death.

[B] Call your doctor even if you’ve had only a single attack, because these symptoms could also signal a wide range of other problems, including thyroid and heart disease. A primary-care physician will first perform a physical exam and probably order an EKG and blood tests to rule out other possible causes of the attacks.

[C] You can be standing at a bus stop or shopping at the mall without any danger in sight, and suddenly, you feel like you’re dying. The attack is generally over in a few minutes, but sometimes symptoms—especially feeling faint and dizzy—can linger for mare than an hour.

[D] Many women report experiencing their first panic attack in late adolescence. But others have no trouble until they are around 50, when their hormone levels often vary wildly. "These are high functioning women who have never seen a psychiatrist before," says Gonsalves. "They start having hot flashes and they don’t sleep. They become acutely anxious. "

[E] If you have felt all of these come on without warning, you may have just suffered a panic attack. These frightening symptoms affect women twice as often as men, although scientists are not sure why.

[F] The cure of panic attacks often depends on the cause. If your attacks are triggered by a physical condition, they should be eliminated by treating the physical cause. If you can’t find the cause, continue looking and using the above tips to control the attacks.

[G] Because of the possible consequences of untreated panic attacks, it’s important to get help early. And fortunately, there is lot of help available.

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