Có 4 dung dịch không màu đựng riêng biệt trong các ống nghiệm bị mất nhãn Na2SO4; Na2CO3; HCl; BaCl2. Không dùng thêm thuốc thử nào khác, trình bày cách nhận biết các dung dịch trên.

Chỉ được dùng thêm một hóa chất, hãy trình bày phương pháp hoá học nhận biết 5 dung dịch chứa trong 5 lọ riêng biệt bị mất nhãn: Al2(SO4)3, CuSO4, FeSO4, MgSO4, H2SO4.

Chỉ dùng một thuốc thử duy nhất hãy nhận biết từng chất trong 4 dd sau: MgCl2; FeCl2; FeCl3; ZnCl2.

Chỉ được dùng quỳ tím, hãy nhận biết các dung dịch riêng biệt mất nhãn sau: NH4HSO4, BaCl2, Ba(OH)2, HCl, H2SO4, NaCl.

Cho biết biểu thức A = $x^{2}$ +15$y^{2}$ +xy+8x+y+2017. Tìm GTNN của biểu thức A

Giải phương trình |x+1|^2016 + |x+2|^2017 = 1

cho 5.6 gam A vào dung dịch HCl . sau phản ứng thu được muối kim loại có hóa trị 1 hoặc 2 hoặc 3 và 2.24 lít khí ở đktc , xác định A

Choose the best answer to complete each of the following sentences. 51. I was enjoying my book but I stopped a program on TV. A. reading to watch B. to read to watch C. to read for watching D. reading for watching 52. ___ to music is a great way to relax. A. To listen B. Listening C. Listen D. Listened 53. She hid the present __________________________ A. so that the children wouldn't find it B. in order to the children not to find it C. for the children not find it D. in order that the children not to find it 54. He _________________ off alone a month ago, and _________________ of since. A. set – hasn’t heard B. set – hasn’t been heard C. was setting – hasn’t heard D. was setting – hasn’t been heard 55. Engineers _________________ the finished bionic contact lenses on rabbits for up to 20 minutes. A. have yet tested B. have already tested C. have performed D. have done 56. The Internet has changed the way we purchase, interact and research since it______________. A. was invented B. invented C. has been invented D. invention Fill the gaps with the correct form of the words in brackets. 57. He made me (do)___________it all over again. 58. I used (live)___________in a caravan 59. You ought (go)___________today. It may (rain)___________tomorrow. 60. Would you like (go)___________now or shall we (wait)___________till the end? 61. They let us ( use)___________this room for our study Correct the mistakes in the following sentences: 62. Progress is (A) been made (B) every day (C) in all parts (D) of the world. 63. (A) Don't (B) forget (C) calling me as soon as you (D) arrive here. 64. Lan (A) should seriously consider (B) to become a singer. She’s (C) a great (D) talent. Rewrite the sentences without changing their meaning: 70. If you arrive at the office earlier than I do, please turn on the air-conditioner. → Should________________________________________________________________________ 71. The car breaks down so often because you don't take good care of it. → Were you _____________________________________________________________________ 72. If I were a bird, I could fly. → Were _________________________________________________________________________ 73. The boy is going to present his project. He prepared for it very carefully. (relative pronoun) ………………………………………………………………………………………. 74. He has repaired the broken vase for two hours. (Passive voice) ………………………………………………………………………………………. 75. Although he had a good salary, he was unhappy in his job. (in spite of) ………………………………………………………………………………………. 76. I have bought a book for James. (Passive voice) ………………………………………………………………………………………. Complete the sentences with the correct relative pronoun or relative adverb. 77. A castle is a place _________ a king or queen lives. 78. An actress is a woman _________ plays in films or theatre plays. 79. This is the girl _________ mother is from Canada. 80. This is the time of the year _________ many people suffer from hay fever

Cho góc xAy =60 độ. Tia AM là tia phân giác của xAy. B là 1 điểm trên tia Ax. Từ B kẻ BC vuông góc với Ay, BD vuông góc với Am. a,So sánh BD và AC b, BD cắt Ay tại E . CMR tam giác ABE đều Giúp mk với mk đang cần gấp

Choose from the list the word that is OPPOSITE in meaning to the underlined word in each question. special/ attend/ unknown/ a few similar/ retain/ passive/ unlucky 26. To have chance to enter the final round, you have to eliminate lots of competitors. 27. Hector Berlioz was one of the most prominent composers of the Romantic period. 28. Many people who do volunteer work think they are more fortunate than others. 29. Economically disadvantaged student often drop out of school, choosing a low-paying job to earn money. 30. We are looking for camp helpers who are hard-working, energetic, and able to organise activities for young children. Use the correct form of the words to complete the sentences. 31. Chopin is one of the greatest Romantic piano composers whose works are often technically ___________. (demand) 32. I find the natural world endlessly ______________(fascinate). 33. He was ____________ to find they’d already gone. (disappoint) 34. Someone who is functionally ___________ can only read and write just a little. (literacy) 35. It's a ___________ organization, depending for its income upon voluntary contributions from the public. (charity) Use the correct form of the words to complete the sentences. 36. Wedding rings remind couples of the ___________ they made to each other when they got married. (COMMIT) 37. The ___________ often keeps the bride calm and helps her ready at the wedding. (BRIDE) 38. Before doing something important, people often choose a ___________ time for it. (FAVOR) 39. There are many ___________ things in the world that we could not explain. (MISTERY) 40. If the first person coming to your house is rich and ___________, then your family will have good fortune that year. (PRESTIGE) Choose a word/phrase from the list and use it in the correct form to complete each sentence. faded/ protection/ deforestation embarrassed/ consumption/ harmony 41. The best singer_______ went to Alan Walker for ― Faded ‖. 42. The ____________________ of the environment from threats such as deforestation, the extinction of rare species, pollution and natural resource depletion is one of the WWF’s missions. 43. The ____________________ caused during the 20th century made the vegetation in this region, which was originally a vast forest refuge for innumerable species, disappear. 44. I walked into this restaurant and there was Andy with a strange woman. He seemed really ______. 45. The _______ of fossil fuels has gradually increased in many countries which is concern for many environmentalists. habitats/ distract/ depletion disruptive/ lighten/ devices 46. Agricultural farms provide important ______________ for many wild plant and animal species. 47. In this situation when you are annoyed and interfered with your device, it becomes ___________. 48. Personal electronic devices which __________ students from their class work are banned in most schools. 49. Using your tablets or smartphones in learning helps you ___________ your backpack. You don’t have to bring so many books to school anymore 50. Mobile learning ___________ are more convenient because they are light and portable.