问题 计算题

(5分)在电缆生产过程中会产生一定量的含铜废料。据报道,在通入空气并加热的条件下,铜与稀硫酸反应转化为硫酸铜。反应的化学方程式:2Cu + 2H2SO4 + O2 2CuSO4 + 2H2O,取490g溶质的质量分数为10%的稀硫酸,通入足量的空气,加入一定量的铜恰好完全反应,假设其他杂质不反应也不溶解,则反应后硫酸铜溶液中溶质的质量分数是多少?(计算结果保留一位小数)

答案

 15.1%

 

题目分析:设反应生成硫酸铜的质量为X,生成水的质量为Y

2Cu + 2H2SO4 + O2 2CuSO4 + 2H2O

196            320    36

490g×10%        X       Y

196:320=49g:X             196:36==49g:Y

X=80g                       Y=8g

溶剂水的质量为:490g-490g×10%+8g=449g

溶液的质量为449g+80g=529g

反应后硫酸铜溶液中溶质的质量分数是80g/529g×100%=15.1%

答:反应后硫酸铜溶液中溶质的质量分数是15.1%

单项选择题
阅读理解

A new study has been carried to test the role of story telling in lowering blood pressure.Dr.Thomas Houston, a professor of the University of Massachusetts Medical School, led a group of scientists that investigated how pre-recorded videos of hypertension (高血压) patients' talking about their medical histories helped another group of patients with high blood pressure to control their condition over several months.

Houston was surprised by their studies that suggested that communication can be a powerful tool in medicine.They showed that those who had had similar experiences, when talking to someone with a similar background, could help change their behavior to become healthier.Hypertension is difficult to control, since it is dependent on diet, exercise and mental state.Medical treatments with drugs, and lifestyle therapies(疗法) have been relatively ineffective because people find it hard to follow those medical requirements.

In the test, his team carefully chose their story-tellers from 230 members of a patients' community with whom they could most easily relate.Next, they divided their study population into two groups.One received three interactive (互动) DVDs containing the tellers' stories of their experiences in living with and treating their hypertension.The other were given educational discs on an unrelated health topic.The study volunteers reported that they had listened to the DVDs, and after three months, those who heard the stories of the hypertensive patients lowered their blood pressure.

While the study did not address how the story-telling influenced the patients' behavior, Houston suspects that watching patients of similar backgrounds who had a similar medical experience helped to motivate them to seek medical help to their hypertension.They found that after six months the difference in blood pressure between those who watched the story-tellers and those who observed the unrelated videos remained, suggesting that the story-telling continued to have an effect.

小题1:We can learn from the text that the pre-recorded videos _________.

A.tell medical histories of hypertension patients

B.introduce some medical treatments of hypertension

C.introduce a good lifestyle for hypertensive patients

D.tell scientific discoveries of the scientist group小题2:Houston was surprised to find that _______.

A.hypertension is really difficult to control

B.communication has some medical effects

C.medical treatments have no effect at all

D.people don't follow the medical requirements小题3:Which of the following is true about the study?

A.The scientists chose 230 patients from a hospital.

B.Both the groups used the same videos about health topic.

C.The two groups lowered blood pressure in different degrees.

D.The story-tellers were hypertension patients as well.小题4:Which of the following could be the best title of the text?

A.The stories of some hypertension patients.

B.Medical treatments of blood pressure.

C.Storytelling may help lower blood pressure.

D.Suggestions about how to lower blood pressure.