Cho 20 gam hỗn hợp Mg và Fe tác dụng với HCl tạo ra 1,72l khí H2 a, viết phương trình và cân bằng phương trình b, tính %m của Fe và Mg

Khi dũa kim loại cần chú ý điều gì?

Đốt cháy hoàn toàn m (g) hợp chất hữu cơ A cần dùng 11,2g khí oxi, thu được 8,8g CO2 và 5,4g H2O. Ở đktc 2,24l khí A có khối lượng 3g. Xác định CTPT của A ?

Giúp nha bài này hơi khó nhưng mà điểm cao 50 điểm ko dài đâu có 6 câu thoi

Mọi người giải hộ em đề toán này vs ạ.

help me cả nhà ơi! vote 5* lun nha

Câu 31. By cutting down trees we ..........the natural habitat of birds and animals. A. damage B. harm C. hurt D. injure Câu 32. The newspaper report contained........important information. A. many B. a lot of C. an D. another Câu 33. Trees and shrubs ........ an important part in preserving land because their roots bind the soil and retain water. A. make B. keep C. have D. play Câu 34. You can't leave the country....... a passport. A. no B. without C. if not D. unless Câu 35. We are facing the possible.........of most of our rain forests. A. vanishing B. disappearance C. extinction D. ruin Mark the letter A, B, C, or D on your answer sheet to indicate the word(s) CLOSEST in meaning to the underlined word(s): Câu 36. They had to think of some other ways of bettering their lives A. improving B. killing C. worsening D. cutting Câu 37. The farmer removed some undeveloped trees to improve the growth of the rest. A. planted B. watered C. eliminated D. fertilized Câu 38. Deforestation is destroying large areas of tropical rain forest. A. changing B. raising C. becoming D. damaging Câu 39. We visited the Nairobi National Park and enjoyed different species of fauna. A. zoo B. animal C. flowers D. plant Câu 40. Contamination is threatening the park and many species of animals living in it. A. elimination B. population C. distribution D. pollution

thể tích ở điều kiện tiaau chuẩn của 2 mol khí O2 là

Giải giúp mình, 20 câu lịch sử 11 hứa 5 sao

Câu 22. I didn’t get a taxi because I didn’t have any money on me. a. If I had some money on me, I would get a taxi. b. If I have some money, I will get a taxi. c. If I had had some money, I would have got a taxi. d. If I did have money, I did get a taxi. Câu 23. The life ......... of sperm whale can be up to seventy years. A. distance B. period C. length D. span Câu 24. Without plants, most of water would ……………………….as soon as it falls. A. run off B. run after C. run away D. run by Câu 25. I still can’t believe it! My bicycle................ last night. A. was stealing B. stolen C. was stolen D. stole Câu 26. It rained all the time, ................was a great pity. A. that B. what C. which D. who Câu 27. Yesterday afternoon, I went to the post office _______ some letters. A. sends B. sent C. send D. to send Câu 28. Tents come in _______ shapes and sizes A. vary B. variety C. various D. variously Câu 29. The room is being ____________ at the moment A. was cleaned B. cleaned C. cleaning D. clean Câu 30. This room isn’t very interesting. They _____________ put some pictures on the walls. A. will B. should C. shouldn’t D. won’t