在溶有Na2CO3和Na2SO4的混合溶液中，加入过量的BaCl2溶液后，得到14.51 g白色沉淀，用置于过量稀硝酸中充分反应后，沉淀量减小为4.66 g，并有气体放出。试计算：
（1）原混合溶液含有的Na2SO4的质量。
（2）产生的气体在标准状况下的体积。
必要的解题过程是：
m(BaCO3)=14.51g-4.66g=9.85g
m(BaSO4)= 4.66g n(BaCO3)= 9.85g÷197g/mol=0.05mol
n(BaSO4)= 4.66g÷233g/mol=0.02mol
m(Na2SO4) = 2.84 g
V(CO2)= 0.05mol×22.4L/mol=1.12L
| 阅读理解。 |
| A man walked into a doctor's examining room. "Put out your tongue," the doctor said. The man put out his tongue, and the doctor looked at it quickly. "OK. You can put your tongue back now," the doctor said. "It's clear what's wrong with you. You need more exercise." "But, doctor," the man said, "I don't think…" "Don't tell me what you think," the doctor said. "I am the doctor, not you. I know what you need. I see hundreds of people like you. None of them get any exercise. They sit in offices all day and in front of the TV in the evening. What you need is to walk quickly for at least 20 minutes a day." "Doctor, you don't understand," the patient said. "I…" "I don't want to hear any excuses," the doctor said. "You must find time for exercise. If you don't, you will get fat and have health problems when you are older." "But I walk every day," the patient said. "Ｏh, yes, and I know what kind of walking that is. You walk a few feet to the train station from your house, a few more feet from the station to your office, and a few more feet from your office to a restaurant for lunch and back. That is not real walking. I'm talking about a walk in the park for twenty minutes every day." "Ｗill you listen to me, doctor!" the patient shouted, getting angry with his doctor who thought he knew everything. "I'm a mailman," the patient went on, "and I walk for seven hours every day!" For a moment the doctor was silent, then he said quietly, "Put your tongue out again, will you?" |
| 1. At first the doctor asked the man . |
[ ] |
| A. to walk to work B. to exercise C. to show his tongue D. to see hundreds of other patients |
| 2. The doctor would not . |
[ ] |
| A. tell the patient what was wrong with him B. let the patient speak C. look at the man's tongue D. let the patient watch TV |
| 3. The doctor told the patient that he . |
[ ] |
| A. should get more exercise B. should stop making excuses C. should watch more TV D. was already too fat |
| 4. The patient was very when he heard what the doctor told him to do. |
[ ] |
| A. angry B. happy C. interested D. tired |
| 5. The doctor . |
[ ] |
| A. gave him some good advice B. walked seven hours a day C. was really a mailman D. knew that he was wrong at last |