Dẫn từ từ V lít khí CO ( đktc) đi qua một ống sứ đựng lượng dư hỗn hợp rắn gồm CuO, $F{e}_2{O}_3$ở nhiệt độ cao. Sau khi các phản ứng xảy ra hoàn toàn, thu được khí X. Dẫn toàn bộ khí X ở trên vào lượng dư dung dịch $Ca(OH{)}_2$ thì tạo thành 20 gam kết tủa. Giá trị của V là:

Người ta có thể sử dụng nước đá khô ( $C{O}_2$rắn) để tạo môi trường lạnh và khô trong việc bảo quản thực phẩm và hoa quả tươi.Vì:

Kim cương và than chì được tạo nên từ cùng nguyên tố cacbon nhưng kim cương rất cứng, còn than chì lại mềm. Đó là do:

Dẫn từ từ V lít khí CO ( đktc) đi qua một ống sứ đựng lượng dư hỗn hợp rắn gồm CuO, $F{e}_2{O}_3$ở nhiệt độ cao. Sau khi các phản ứng xảy ra hoàn toàn, thu được khí X. Dẫn toàn bộ khí X ở trên vào lượng dư dung dịch $Ca(OH{)}_2$ thì tạo thành 20 gam kết tủa. Giá trị của V là:

Phương trình ion thu gọn: 2H⁺ (dd) + (dd) H₂SiO₃ (r)

ứng với phản ứng nào sau đây?

Có 5 lọ mất nhãn đựng 5 chất bột màu trắng : $NaCl, N{a}_{2}C{O}_3, N{a}_{2}S{O}_4, BaC{O}_3, BaS{O}_4$. Chỉ dùng nước và $C{O}_2$thì có thể nhận ra mấy chất?

Cho từ từ dung dịch chứa a mol HCl vào dung dịch chứa b mol $N{a}_{2}C{O}_3$đồng thời khuấy đều, thu được V lít khí (ở đktc) và dung dịch X. Khi cho dư nước vôi trong vào dung dịch X thấy có xuất hiện kết tủa. Biểu thức liên hệ giữa V với a, b là:

Một chất Y có tính chất sau:

- Không màu, rất độc.

- Cháy trong không khí với ngọn lửa xanh và sinh ra chất khí làm đục nước vôi trong.

Y có thể là:

Khử 6,4 gam CuO bằng $H_2$ ở nhiệt độ cao thu được chất rắn A và hỗn hợp khí B. Dẫn toàn bộ lượng khí B qua bình đựng $H_{2}S{O}_4$đậm đặc, thấy khối lượng bình tăng 0,9 gam. Thành phần % CuO bị khử trong phản ứng trên là:

Cacbon và oxi phản ứng theo phương trình hoá học sau: $C + O_2 \to C{O}_2$.

Nếu cho 1,2gam cacbon phản ứng với 1,68 lít khí oxi(đkc) thì lượng tối đâccbon đioxit sinh ra là:

Silic phản ứng được với nhóm chất nào sau đây?

Chất nào sau đây không phải là nguyên liệu của công nghiệp sản xuất xi măng?

Sục 11,2 lít $C{O}_2$(đktc) vào 200(ml) dung dịch $Ba(OH{)}_2$ 2M. Khối lượng kết tủa thu được là:

Cho bột than dư vào hỗn hợp hai oxit $F{e}_2{O}_3$ và CuO đun nóng để phản ứng xảy ra hoàn toàn thu được 4g hỗn hợp kim loại và 1,68 lít khí (đktc). Khối lượng hỗn hợp hai oxit ban đầu là:

C và Si cùng phản ứng với tất cả các chất trong nhóm nào sau đây ?

Sự phân cực trong phân tử $C{O}_2$là:

Hãy cho biết trong các cặp chất sau đây, cặp nào có thể cùng tồn tại trong một dung dịch?

Cho 0,14 mol $C{O}_2$hấp thụ hết vào dung dịch chứa 0,08mol $Ca(OH{)}_2$. khối lượng dung dịch còn lại tăng là bao nhiêu?

Để phân biệt khí $C{O}_2$ và khí $S{O}_2$, có thể dùng:

Dãy biến hóa nào sau đây đúng với tính chất của X (X là nguyên tố C hoặc Si) và các hợp chất của X?

Khí nào dưới đây có khối lượng riêng nhỏ nhất đo ở cùng điều kiện nhiệt độ và áp suất?

Read the following pasage and mark the letter A, B, C or D to indicate the correct answer to each of the questions:

                                                                                WOMEN

In developing countries, where three fourths of the world’s population live, sixty percent of the people who can’t read and write are women. Being illiterate doesn’t mean they are not intelligent. It does mean it is difficult for them to change their lives. They produce more than half of the food. In Africa eighty percent of all agricultural work is done by women. There are many programs to help poor countries develop their agriculture. However, for years, these programs provided money and training for men.

In parts of Africa, this is a typical day for a village woman. At 4:45 a.m, she gets up, washes and eats. It takes her a halfhour to walk to the fields, and she works there until 3:00p.m. She collects firewood and gets home at 4:00. She spends the next hour and a haft preparing food to cook. Then she collects water for another hour. From 6:30 to 8:30 she cooks.After dinner, she spends an hour washing the dishes and her children. She goes to bed at 9:30 p.m. International organizations and programs run by developed nations are starting to help women, as well as men, improvetheir agricultural production. Governments have already passed some laws affecting women because of the UNO Decadefor Women. The UNO report will affect the changes now happening in the family and society.

Question: Which of these statements is NOT TRUE?         

Read the following pasage and mark the letter A, B, C or D to indicate the correct answer to each of the questions:

                                                                                WOMEN

In developing countries, where three fourths of the world’s population live, sixty percent of the people who can’t read and write are women. Being illiterate doesn’t mean they are not intelligent. It does mean it is difficult for them to change their lives. They produce more than half of the food. In Africa eighty percent of all agricultural work is done by women. There are many programs to help poor countries develop their agriculture. However, for years, these programs provided money and training for men.

In parts of Africa, this is a typical day for a village woman. At 4:45 a.m, she gets up, washes and eats. It takes her a halfhour to walk to the fields, and she works there until 3:00p.m. She collects firewood and gets home at 4:00. She spends the next hour and a haft preparing food to cook. Then she collects water for another hour. From 6:30 to 8:30 she cooks.After dinner, she spends an hour washing the dishes and her children. She goes to bed at 9:30 p.m. International organizations and programs run by developed nations are starting to help women, as well as men, improvetheir agricultural production. Governments have already passed some laws affecting women because of the UNO Decadefor Women. The UNO report will affect the changes now happening in the family and society.

Question: By whom (what) was the Decade for Women organized?         

Read the following pasage and mark the letter A, B, C or D to indicate the correct answer to each of the questions:

                                                                                WOMEN

In developing countries, where three fourths of the world’s population live, sixty percent of the people who can’t read and write are women. Being illiterate doesn’t mean they are not intelligent. It does mean it is difficult for them to change their lives. They produce more than half of the food. In Africa eighty percent of all agricultural work is done by women. There are many programs to help poor countries develop their agriculture. However, for years, these programs provided money and training for men.

In parts of Africa, this is a typical day for a village woman. At 4:45 a.m, she gets up, washes and eats. It takes her a halfhour to walk to the fields, and she works there until 3:00p.m. She collects firewood and gets home at 4:00. She spends the next hour and a haft preparing food to cook. Then she collects water for another hour. From 6:30 to 8:30 she cooks.After dinner, she spends an hour washing the dishes and her children. She goes to bed at 9:30 p.m. International organizations and programs run by developed nations are starting to help women, as well as men, improvetheir agricultural production. Governments have already passed some laws affecting women because of the UNO Decadefor Women. The UNO report will affect the changes now happening in the family and society.

Question: The passage would most likely be followed by details about _______.         

Read the following pasage and mark the letter A, B, C or D to indicate the correct answer to each of the questions:

 In science, a theory is a reasonable explanation of observed events that are related. A theory often involves an imaginary model that helps scientists picture the way an observed event could be produced. A good example of this is found in the kinetic molecular theory, in which gases are pictured as being made up of many small particles that are in constant motion. 

 A useful theory, in addition to explaining past observation, helps to predict events that have not as yet been observed. After a theory has been publicized, scientists design experiments to test the theory. If observations confirm the scientists' predictions, the theory is supported. If observations do not confirm the predictions, the scientists must search further. There may be a fault in the experiment, or the theory may have to be revised or rejected.

 Science involves imagination and creative thinking as well as collecting information and performing experiments. Facts by themselves are not science. As the mathematician Jules Henri Poincare said: "Science is built with facts just as a house is built with bricks, but a collection of facts cannot be called science any more than a pile of bricks can be called a house." 

 Most scientists start an investigation by finding out what other scientists have learned about a particular problem. After known facts have been gathered, the scientist comes to the part of the investigation that requires considerable imagination. Possible solutions to the problem are formulated. These possible solutions are called hypotheses. In a way, any hypothesis is a leap into the unknown. It extends the scientist's thinking beyond the known facts. The scientist plans experiments, performs calculations, and makes observations to test hypotheses. For without hypotheses, further investigation lacks purpose and direction. When hypotheses are confirmed, they are incorporated into theories. 

Question: Which of the following is the main subject of the passage?         

Read the following pasage and mark the letter A, B, C or D to indicate the correct answer to each of the questions:

 In science, a theory is a reasonable explanation of observed events that are related. A theory often involves an imaginary model that helps scientists picture the way an observed event could be produced. A good example of this is found in the kinetic molecular theory, in which gases are pictured as being made up of many small particles that are in constant motion. 

 A useful theory, in addition to explaining past observation, helps to predict events that have not as yet been observed. After a theory has been publicized, scientists design experiments to test the theory. If observations confirm the scientists' predictions, the theory is supported. If observations do not confirm the predictions, the scientists must search further. There may be a fault in the experiment, or the theory may have to be revised or rejected.

 Science involves imagination and creative thinking as well as collecting information and performing experiments. Facts by themselves are not science. As the mathematician Jules Henri Poincare said: "Science is built with facts just as a house is built with bricks, but a collection of facts cannot be called science any more than a pile of bricks can be called a house." 

 Most scientists start an investigation by finding out what other scientists have learned about a particular problem. After known facts have been gathered, the scientist comes to the part of the investigation that requires considerable imagination. Possible solutions to the problem are formulated. These possible solutions are called hypotheses. In a way, any hypothesis is a leap into the unknown. It extends the scientist's thinking beyond the known facts. The scientist plans experiments, performs calculations, and makes observations to test hypotheses. For without hypotheses, further investigation lacks purpose and direction. When hypotheses are confirmed, they are incorporated into theories. 

Question: The word "related" in paragraph 1 is closest in meaning to _______.           

Read the following passage and mark the letter A, B, C, or D to indicate the correct answer to each of the questions:

The rules of etiquette in American restaurants depend upon a number of factors the physical location of the restaurant, e.g., rural or urban; the type of restaurant, e.g., informal or formal; and certain standards that are more universal. In other words, some standards 5 of etiquette vary significantly while other standards apply almost anywhere. Learning the proper etiquette in a particular type of restaurant in a particular area may sometimes require instruction, but more commonly it simply requires sensitivity and experience. For example, while it is acceptable to read a magazine in a coffee shop, it is 10 inappropriate to do the same in a more luxurious setting. And, if you are eating in a very rustic setting it may be fine to tuck your napkin into your shirt, but if you are in a sophisticated urban restaurant this behavior would demonstrate a lack of manners. It is safe to say, however, that in virtually every restaurant it is unacceptable 15 to indiscriminately throw your food on the floor. The conclusion we can most likely draw from the above is that while the types and locations of restaurants determine etiquette appropriate to them, some rules apply to all restaurants.   

Question: Which of the following words is most similar to the meaning of “rustic” ?         

Read the following passage and mark the letter A, B, C, or D to indicate the correct answer to each of the questions:

The rules of etiquette in American restaurants depend upon a number of factors the physical location of the restaurant, e.g., rural or urban; the type of restaurant, e.g., informal or formal; and certain standards that are more universal. In other words, some standards 5 of etiquette vary significantly while other standards apply almost anywhere. Learning the proper etiquette in a particular type of restaurant in a particular area may sometimes require instruction, but more commonly it simply requires sensitivity and experience. For example, while it is acceptable to read a magazine in a coffee shop, it is 10 inappropriate to do the same in a more luxurious setting. And, if you are eating in a very rustic setting it may be fine to tuck your napkin into your shirt, but if you are in a sophisticated urban restaurant this behavior would demonstrate a lack of manners. It is safe to say, however, that in virtually every restaurant it is unacceptable 15 to indiscriminately throw your food on the floor. The conclusion we can most likely draw from the above is that while the types and locations of restaurants determine etiquette appropriate to them, some rules apply to all restaurants.

Question: Which of the following is closest in meaning to the word “tuck” in line 7?         

Read the following passage and mark the letter A, B, C, or D to indicate the correct answer to each of the questions:

The rules of etiquette in American restaurants depend upon a number of factors the physical location of the restaurant, e.g., rural or urban; the type of restaurant, e.g., informal or formal; and certain standards that are more universal. In other words, some standards 5 of etiquette vary significantly while other standards apply almost anywhere. Learning the proper etiquette in a particular type of restaurant in a particular area may sometimes require instruction, but more commonly it simply requires sensitivity and experience. For example, while it is acceptable to read a magazine in a coffee shop, it is 10 inappropriate to do the same in a more luxurious setting. And, if you are eating in a very rustic setting it may be fine to tuck your napkin into your shirt, but if you are in a sophisticated urban restaurant this behavior would demonstrate a lack of manners. It is safe to say, however, that in virtually every restaurant it is unacceptable 15 to indiscriminately throw your food on the floor. The conclusion we can most likely draw from the above is that while the types and locations of restaurants determine etiquette appropriate to them, some rules apply to all restaurants.   

Question: According to the passage, which of the following is a universal rule of etiquette?         

Read the following passage and mark the letter A, B, C, or D to indicate the correct answer to each of the questions:

The rules of etiquette in American restaurants depend upon a number of factors the physical location of the restaurant, e.g., rural or urban; the type of restaurant, e.g., informal or formal; and certain standards that are more universal. In other words, some standards 5 of etiquette vary significantly while other standards apply almost anywhere. Learning the proper etiquette in a particular type of restaurant in a particular area may sometimes require instruction, but more commonly it simply requires sensitivity and experience. For example, while it is acceptable to read a magazine in a coffee shop, it is 10 inappropriate to do the same in a more luxurious setting. And, if you are eating in a very rustic setting it may be fine to tuck your napkin into your shirt, but if you are in a sophisticated urban restaurant this behavior would demonstrate a lack of manners. It is safe to say, however, that in virtually every restaurant it is unacceptable 15 to indiscriminately throw your food on the floor. The conclusion we can most likely draw from the above is that while the types and locations of restaurants determine etiquette appropriate to them, some rules apply to all restaurants.   

Question: According to the passage, _______ requires sensitivity and experience?         

Read the following passage and mark the letter A, B, C, or D to indicate the correct answer to each of the questions:

The rules of etiquette in American restaurants depend upon a number of factors the physical location of the restaurant, e.g., rural or urban; the type of restaurant, e.g., informal or formal; and certain standards that are more universal. In other words, some standards 5 of etiquette vary significantly while other standards apply almost anywhere. Learning the proper etiquette in a particular type of restaurant in a particular area may sometimes require instruction, but more commonly it simply requires sensitivity and experience. For example, while it is acceptable to read a magazine in a coffee shop, it is 10 inappropriate to do the same in a more luxurious setting. And, if you are eating in a very rustic setting it may be fine to tuck your napkin into your shirt, but if you are in a sophisticated urban restaurant this behavior would demonstrate a lack of manners. It is safe to say, however, that in virtually every restaurant it is unacceptable 15 to indiscriminately throw your food on the floor. The conclusion we can most likely draw from the above is that while the types and locations of restaurants determine etiquette appropriate to them, some rules apply to all restaurants.

Question: The word “sophisticated” in line 7 could best be replaced by?