Nếu tháo 1 trong hai đèn thì đèn còn lại sẻ tắc. Vì là mắc nối tiếp nên khi tháo 1 đèn ra thì mạch bị hở đèn còn lại sẻ không sáng

Tiến hành các thí nghiệm sau:

(a) Cho Ca vào dung dịch CuSO₄.

(b) Dẫn khí H₂ qua Al₂O₃ nung nóng.

(c) Cho dung dịch HCl vào dung dịch Fe(NO₃)₂.

(d) Cho Cr vào dung dịch KOH đặc, nóng.

Số thí nghiệm xảy ra phản ứng là

A. 3.

B. 2.

C. 1.

D. 4

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

Although they are an inexpensive supplier of vitamins, minerals, and high-quality protein, eggs also contain a high level of blood cholesterol, one of the major causes of heart diseases. One egg yolk, in fact, contains a little more than two-thirds of the suggested daily cholesterol limit. This knowledge has driven egg sales to plummet in recent years, which in turn has brought about the development of several alternatives to eating regular eggs. One alternative is to eat substitute eggs. These egg substitutes are not really eggs, but they look somewhat like eggs when they are cooked. They have the advantage of having low cholesterol rates, and they can be scrambled or used in baking. One disadvantage, however, is that they are not good for frying, poaching, or boiling. A second alternative to regular eggs is a new type of egg, sometimes called 'designer' eggs. These eggs are produced by hens that are fed low-flat diets consisting of ingredients such as canola oil, flax, and rice bran. In spite of their diet, however, these hens produce eggs that contain the same amount of cholesterol as regular eggs. Yet, the producers of these eggs claim that eating their eggs will not raise the blood cholesterol in humans.

         Egg producers claim that their product has been portrayed unfairly. They cite scientific studies to back up their claim. And, in fact, studies on the relationship between eggs and human cholesterol levels have brought mixed result. It may be that it is not the type of eggs that is the main determinant of cholesterol but the person who is eating the eggs. Some people may be more sensitive to cholesterol derived from food than other people. In fact, there is evidence that certain dietary fats stimulate the body's production of blood cholesterol. Consequently, while it still makes sense to limit one's intake of eggs, even designer eggs, it seems that doing this without regulating dietary fat will probably not help reduce the blood cholesterol level.

According to the passage, egg substitutes cannot be used to make any of the following types of eggs EXCEPT ________?

A. boiled    

B. poached      

C. scrambled    

D. fried

Ancient Egyptians mummified the dead bodies through the use of chemicals, ________ ancient Peruvians did through natural processes.

A. because  

B. whereas  

C. whether or not 

D. even though

Read the following passage and mark the letter A, B, C, or D on your answer sheet to indicate the correct answer to each of the questions from 44 to 55.

         Panel painting, common in thirteenth- and fourteenth-century Europe, involved a painstaking, laborious process. Wooden planks were joined, covered with gesso to prepare the surface for painting, and then polished smooth with special tools. On this perfect surface, the artist would sketch a composition with chalk, refine it with inks, and then begin the deliberate process of applying thin layers of egg tempera paint (egg yolk in which pigments are suspended) with small brushes. The successive layering of these meticulously applied paints produced the final translucent colors.

         Backgrounds of gold were made by carefully applying sheets of gold leaf, and then embellishing of decorating the gold leaf by punching it with a metal rod on which a pattern had been embossed. Every step in the process was slow and deliberate. The quick-drying tempera demanded that the artist know exactly where each stroke be placed before the brush met the panel, and it required the use of fine brushes. It was, therefore, an ideal technique for emphasizing the hard linear edges and pure, fine areas of color that were so much a part of the overall aesthetic of the time. The notion that an artist could or would dash off an idea in a fit of spontaneous inspiration was completely alien to these deliberately produced works.

         Furthermore, making these paintings was so time-consuming that it demanded assistance. All such work was done by collective enterprise in the workshops. The painter or master who is credited with having created the painting may have designed the work and overseen its production, but it is highly unlikely that the artist’s hand applied every stroke of the brush. More likely, numerous assistants, who had been trained to imitate the artist’s style, applied the paint. The carpenter’s shop probably provided the frame and perhaps supplied the panel, and yet another shop supplied the gold. Thus, not only many hands, but also many shops were involved in the final product.

         In spite of problems with their condition, restoration, and preservation, many panel paintings have survived, and today many of them are housed in museum collections. 

According to the passage, what was the first step in making a panel painting?

A. Mixing the paint

B. Making ink drawings

C. Preparing the panel

D. Buying the gold leaf

Các kim loại nào sau đây đều phản ứng với dung dịch CuCl2?

A. Na, Mg, Ag.

B. Fe, Na, Mg.

C. Ba, Mg, Hg.

D. Na, Ba, Ag.

Amin nào không cùng bậc với amin còn lại: 

A. Đimetylamin

B. Phenylamin

C. Metylamin

D. Propan – 2-amin

Có hai lọ không ghi nhãn đựng dung dịch AlCl3 và dung dịch NaOH. Không dùng thêm chất nào khác, làm thế nào để nhận biết mỗi chất?

Cation M+ có cấu hình electron ở phân lớp ngoài cùng là 2s22p6. M+ là cation nào sau đây?

A. Ag+.

B. Cu2+.

C. Na+.

D. K+.