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duongvanvu1966
2 năm trước
1: cho xenlulozơ phản ứng với anđehit axetic có H2SO4 đặc làm xúc tác thu được 11,1 gam hỗn hợp X gồm xenlulozơ triaxetat , xenlulozơ điaxetat và 6,6 gam CH3COOH. Thành phần phần trăm theo khối lượng của xenlulozơ triaxetat và xenlulozơ điaxetat trong X lần lượt là ??
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Chọn thì thích hợp nhất để hoàn thành các câu sau: 37. I ______ my writing by 3 o'clock this afternoon. A. will finish B. finish C. will have finished D. finished 38. How ______ since we ______ school? A. will you / left B. are you / left C. have you been / had left D. have you been / left 39. When I last ___________ Jane, she ____________ to find a job. A. have seen/ tried B. saw/ tried C. see/ is trying D. saw/ was trying 40. Next week when there ______ a full moon, the ocean tides will be higher. A. is B. will be C. is being D. will have been 41. I sat near a window whenever I ______ a bus. A. have taken B. had took C. took D. take 42. When I last saw him, he _________in London. A. is living B. was living C. has lived D. has been living 43. We ________________Mary since last Saturday. A. don't see B. hadn't seen C. didn't see D. haven't seen 44. The train __________________haft an hour ago. A. has left B. had left C. left D. has been leaving 45. By Christmas, I ________________for Mr. Smith for six years. A. shall have been working B. shall be working C. shall work D. have been working 46. I'll come and see you before I ____________for HCM City. A. will leave B. shall leave C. have left D. leave

Mark the letter A, B, C, or D on your answer sheet to indicate the sentence that best combines each pair of sentences in the following questions. 37. The weather was so bad. We couldn’t go out. A. The weather was so bad because we couldn’t go out. B. Because of the weather so bad, we couldn’t go out. C. Because of the bad weather, we couldn’t go out. D. We couldn’t go out because the bad weather. 38. They travel much. They know about the world good. A. The more they travel, the gooder they know about the world. B. The more they travel, the more good they know about the world. C. The much they travel, the better they know about the world. D. The more they travel, the better they know about the world. 39. We will have to cancel the show. We are trying to sell more tickets. A. Unless we sell more tickets, we will have to cancel the show. B. Unless we don’t sell more tickets, we will have to cancel the show. C. Unless we sell more tickets, we won’t have to cancel the show. D. Unless we sells more tickets, we will have to cancel the show. 40. Martin is not tall. His father is not tall. A. Martin is not tall, his father is not, too. B. Martin is not tall, his father is not, either. C. Either Martin or his father are not tall. D. Martin is not tall, his father is not, neither.

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