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a)81x^4(z^2-y^2)-z^2+y^2\\\\\\B)x^2(y-z)+y^2(z-x)+z^2(x-y)

Bài 6: Cho 1,6g đồng (II) oxit tác dụng với 100g dung dịch axit sunfuric có nồng độ 20%. a) Viết phương trình phản ứng hóa học. b) Tính nồng độ phần trăm các chất có trong dung dịch sau khi phản ứng kết thúc.

câu 3: 2,84 gam hỗn hợp MgCO3, CaCO3 tác dụng hoàn toàn với 400 ml dung dịch HCl 0,2M thu được khí X và dung dịch Y. Để trung hòa dung dịch Y cần 200 ml dung dịch KOH 0,1M. Tính khối lượng các chất ban đầu, tính nồng độ mol các chất sau phản ứng.

Giải thích chi tiết vào ( KHÔNG ĐƯỢC GIẢI THÍCH BẰNG CÁCH DỊCH) XIV. Underline the correct words. (U5) 1. She bought a loaf/ bowl/ bar of bread so we can make sandwiches. 2. We’ve already eaten a tube/ packet/ slice of biscuits! 3. Would you like a bowl/piece/glass of lemonade? 4. There is a piece/ carton/ kilo of milk in the fridge. 5. Could you cut me a smaller slice/ spoon/ bunch of ham? 6. You can have a loaf/ piece/ pot of cake after you’ve eaten your vegetables! 7. See round the grocer’s for a bottle/ tin/ tube of sardines. 8. She ate a glass/ slice/ bowl of noodles yesterday morning. 9. Anna always eats a slice/ bar/ loaf of chocolate on her way to school. 10. He got a can/ piece/ carton of Coke from the fridge because he was thirsty.

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Everyone wants to reduce pollution. But the pollution problem is as complicated (1)__________it is serious. It is complicated because much (2)__________is caused by things that benefit people. For example, exhaust (3)_________automobiles causes a large percentage of all air pollution. (4)_________ the automobiles provide transportation for millions of people. Factories (5)__________much of the material which pollutes air and water, but factories give employment to a large number of people. Thus, to (6)__________or greatly reduce pollution immediately, people would have to stop using many things that benefit them. Most of the people do not want to do that, of course. But pollution can be (7)__________reduced in several ways. (8)__________and engineers can work to find ways to lessen the (9)__________of pollution that such things as automobiles and factories cause. Governments can pass and enforce laws that require businesses and individuals to stop, or cut (10)__________on certain polluting activities. 1. A. for B. as C. because D. since 2. A. polluter B. pollutant C. polluting D. pollution 3. A. in B. at C. from D. for 4. A. Therefore B. However C. Moreover D. But 5. A. discharge B. offer C. emit D. dissolve 6. A. cause B. end C. increase D. pause 7. A. increasingly B. hopelessly C. gradually D. dangerously 8. A. Scientists B. Doctors C. Lecturers D. Botanists 9. A. number B. figures C. numbers D. amount 10. A. up B. off C. down D. into

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Giải thích chi tiết vào ( KHÔNG ĐƯỢC GIẢI THÍCH BẰNG CÁCH DỊCH) XIII. Fill in each blank with a suitable preposition. (U5) 1. Is there any milk _________ the fridge? 2. There was a lot of food left over _________ the party. 3. You can warm _________ the leftovers in the microwave. 4. Beat the eggs together _________ salt, pepper and cold water. 5. Serve the pancakes _________ some vegetables or fruits. 6. Pho is a special kind _________ Vietnamese soup. 7. Pour about ¼ cup of mixture _________ the pan at a time. 8. The broth for pho bo is made _________ stewing cow bones _________ a long time. 9. Simmer the sauce _________ a low heat. 10. Cut the meat _________ small pieces.