问题 填空题

根据右图A、B、C三种固体的溶解度曲线回答:

(1)P点的含义是                       

(2)要使C的饱和溶液成为不饱和溶液,可采用的一种

方法是                       

(3)要从含有少量A的B溶液中得到较多的B晶体,通常采用的方法是                   

(4)t1℃时,将15gA加入到装有50g水的烧杯中,充分搅拌,所得溶液的溶质质量分数为     (结果精确至0.1%)。

(5)将t2℃时三种物质的饱和溶液分别降温到t1℃,所得溶液中溶质的质量分数最小的是           (填序号)。

答案

(1)t1℃时,A,C的溶解度相等(答案合理即可)

(2)降温(答案合理即可)(3)蒸发结晶(4)16.7%(5)C

题目分析:(1)P点的含义是)t1℃时,A,C的溶解度相等;

(2)要使C的饱和溶液成为不饱和溶液,可采用的一种方法是降温(或者加入溶剂);

(3)要从含有少量A的B溶液中得到较多的B晶体,通常采用的方法是蒸发结晶,因为B得溶解度受温度影响不大;

(4)t1℃时,A的溶解度是20g,50克水最多溶解10gA,故将15gA加入到装有50g水的烧杯中,充分搅拌,所得溶液的溶质质量分数为=16.7%;

(5)将t2℃时三种物质的饱和溶液分别降温到t1℃,所得溶液中溶质的质量分数最小的是C。因为t2℃时三种物质中,C的溶解度最小,溶液中含有的溶质最少,降温后,虽然它的溶解度增大了,但溶液中溶质的质量没有增大,其质量分数还是最小的。

点评:溶解度曲线图中,曲线的交叉点,表示该温度下,各物质的溶解度相等;

溶质质量分数=

解答题
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If you see someone drowning, speed is very important. Once you get him out of the water, if he isn't breathing, you have four minutes before his brain is completely destroyed. Support his neck, move his head back and press his chin upwards. This stops the tongue blocking the airway in the throat and is sometimes enough to get him breathing again. If that doesn't work, start mouth-to-mouth breathing. Press his nostrils (the two holes at the end of your nose, through which you breathe and smell things) together with your fingers. Open your mouth and take a deep breath. Blow into his lungs until his chest rises, then remove your mouth and watch his chest fall. Repeat twelve times a minute. Keep doing until professional help arrives.

To bring a child back to life, keep your lips around his mouth and gently blow into his mouth. Give the first four breaths as quickly as possible to fill the blood with oxygen. If, in spite of your efforts, he starts turning a blue-grey colour, and you can feel no pulse(脉搏), then pressing is the last chance of saving his life.

With arms straight, rock forwards, pressing down on the lower half of the breastbone. Don't be too hard or you may break a rib. Check how effective you are by seeing if his colour improves or his pulse becomes independent to your chest pressing. If this happens, stop the pressing. Otherwise continue until rescue arrives.

小题1:If you want to save someone drowning, you __________.

A.have to pull off his clothes first .

B.should try to get him out of water as quickly as possible.

C.should first make out who he is.

D.ought to throw a life coat to him first .小题2:Once a person stops breathing, it means ___________.

A.you have no more than 4 minutes to bring him to life again .

B.his brain is completely damaged .

C.he has passed away.

D.there is no way to save his life .小题3:To press his chin upwards is a way to _____________.

A.keep the tongue from blocking the airway in the throat .

B.prevent the tongue from stopping the airway in the throat .

C.wipe the tongue out of the throat .

D.see if he can possibly be saved .小题4:If the drowning boy has no pulse,_____________.

A.press his chin upwards is enough to get him breathing .

B.blow air into his mouth is sure to save his life .

C.press his nostrils together with your fingers can work .

D.press is the last chance of saving his life .小题5:Which of the following statement is true?

A.Don’t stop pressing his chest, if the drowning man starts breathing again.

B.If you see someone drowning, you must give him mouth-to-mouth breathing.

C.If a man does not breathe for four minutes, his brain will be completely destroyed.

D.When pressing, you can do it as hard as you can.