Hợp chất cacbonyl C₄H₈O có bao nhiêu đồng phân?

Tráng gương hoàn toàn hợp chất hữu cơ X bằng $AgN{O}_3/N{H}_3$ thu được hỗn hợp sản phẩm chỉ gồm các chất vô cơ. X có cấu tạo là :

Đốt cháy anđehit A được A là :

Hai chất hữu cơ X, Y có cùng công thức phân tử C₃H₄O₂.

- X tác dụng với CaCO₃ tạo CO₂.

- Y tác dụng với Ag₂O/NH₃ tạo Ag.

Công thức cấu tạo thu gọn phù hợp của X, Y lần lượt được chọn là:

Quá trình nào sau đây không tạo ra anđehit axetic ?

Cho Na dư tác dụng với a gam dung dịch $C{H}_{3}COOH$. Kết thúc phản ứng, thấy khối lượng $H_2$ sinh ra là $\frac{11a}{240}$ gam. Vậy nồng độ C% dung dịch axit là :

Nhiệt độ sôi của ancol etylic (I), anđehit axetic (II), axit axetic (III) và axit propionic (IV) sắp xếp theo thứ tự giảm dần là :

Có 5 bình đựng 5 chất lỏng sau : Dung dịch HCOOH, dung dịch $C{H}_{3}COOH$, ancol etylic, glixerol và dung dịch anđehit axetic. Dùng những hóa chất nào sau đây để phân biệt được 5 chất lỏng trên ?

Cho sơ đồ chuyển hóa sau:

HO-CH₂-COONa  X  Y  HCOOH.

Các chất X, Y có thể là:

Hợp chất cacbonyl C₄H₈O có bao nhiêu đồng phân?

Gọi tên hợp chất có CTCT như sau theo danh pháp thông thường.

$C{H}_3–C{H}_2–C{H}_2–CO–C{H}_2–C\equiv CH$

Read the following passage and mark the letter A, B, C or D on your answer sheet to indicate the correct word or phrase that best fits each of the numbered blanks from 15 to 19:

Fashions have always changed with time. No (15) ________ Roman girls worried about having the latest hairstyle and boys in Ancient Egypt wanted to have sandals that were cool and not the sensible ones their mothers preferred. Look (16) ________over recent times, there seem to be two main differences in the way fashions have changed compared to earlier time. Firstly, (17) ________ more people have a choice of clothes available to them. There are few places in the world where the trainers, the caps or the T-shirts of teenagers do not change from one year to the next. Secondly, styles are (18) ________within a much shorter time than they used to be. For instance, in the 1960s, (19) ________ had the same low waists and narrow skirts as forty years before. In the early years of the 21st century, the shops are full of long skirts and colored scarves like the ones in fashion only thirty years before. Soon, we will find that the really fashionable people look no different from the rest of us, because it is only ten years since their clothes were in fashion before!  

Question 15:

Read the following passage and mark the letter A, B, C or D on your answer sheet to indicate the correct word or phrase that best fits each of the numbered blanks from 27 to 38:

On a winter afternoon, a dozen male Northern fur seals are on an island off south - western Alaska. To look at them, fighting for territory on the rocks, it’s hard to imagine that they are at the (27)____________of a baffling scientific mystery: why is this species beginning to disappear? These seals - which can weigh up to 270 kilograms - have an important and symbolic (28)_________in Alaska’s history. Their soft and luxurious fur, the coveted prize during the huge commercial sea harvests that were legal here in the Bering Sea through the early 20th century, was once so valuable it (29)_________Alaska’s economy. Starting in the 1950s, for reasons that are (30)_______because the harvests by then tended to be fairly small, the seal population began a slow decline. But lately it has been falling drastically, declining at an alarming (31)________of 6 per cent a year since 1998. From a (32)_________ of more than 2 million in Alaska in 1948, their numbers have fallen to about 1 million. So (33)________, no one has been able to establish a precise cause for this, although theories (34)___________. The seal's food supply may be (35)________, or another species may be (36)________on the seals - perhaps killer whales, which no longer have as many great whales to eat because of harvesting of those mammals. Some people have suggested that the decline can be (37)______to entanglement in fishing nets, but scientists say they doubt that this alone could (38)_________the recent population decline.

Question 37:

Read the following passage and mark the letter A, B, C or D on your answer sheet to indicate the correct word or phrase that best fits each of the numbered blanks from 27 to 38:

On a winter afternoon, a dozen male Northern fur seals are on an island off south - western Alaska. To look at them, fighting for territory on the rocks, it’s hard to imagine that they are at the (27)____________of a baffling scientific mystery: why is this species beginning to disappear? These seals - which can weigh up to 270 kilograms - have an important and symbolic (28)_________in Alaska’s history. Their soft and luxurious fur, the coveted prize during the huge commercial sea harvests that were legal here in the Bering Sea through the early 20th century, was once so valuable it (29)_________Alaska’s economy. Starting in the 1950s, for reasons that are (30)_______because the harvests by then tended to be fairly small, the seal population began a slow decline. But lately it has been falling drastically, declining at an alarming (31)________of 6 per cent a year since 1998. From a (32)_________ of more than 2 million in Alaska in 1948, their numbers have fallen to about 1 million. So (33)________, no one has been able to establish a precise cause for this, although theories (34)___________. The seal's food supply may be (35)________, or another species may be (36)________on the seals - perhaps killer whales, which no longer have as many great whales to eat because of harvesting of those mammals. Some people have suggested that the decline can be (37)______to entanglement in fishing nets, but scientists say they doubt that this alone could (38)_________the recent population decline.

Question 36:

Read the following passage and mark the letter A, B, C or D on your answer sheet to indicate the correct word or phrase that best fits each of the numbered blanks from 27 to 38:

On a winter afternoon, a dozen male Northern fur seals are on an island off south - western Alaska. To look at them, fighting for territory on the rocks, it’s hard to imagine that they are at the (27)____________of a baffling scientific mystery: why is this species beginning to disappear? These seals - which can weigh up to 270 kilograms - have an important and symbolic (28)_________in Alaska’s history. Their soft and luxurious fur, the coveted prize during the huge commercial sea harvests that were legal here in the Bering Sea through the early 20th century, was once so valuable it (29)_________Alaska’s economy. Starting in the 1950s, for reasons that are (30)_______because the harvests by then tended to be fairly small, the seal population began a slow decline. But lately it has been falling drastically, declining at an alarming (31)________of 6 per cent a year since 1998. From a (32)_________ of more than 2 million in Alaska in 1948, their numbers have fallen to about 1 million. So (33)________, no one has been able to establish a precise cause for this, although theories (34)___________. The seal's food supply may be (35)________, or another species may be (36)________on the seals - perhaps killer whales, which no longer have as many great whales to eat because of harvesting of those mammals. Some people have suggested that the decline can be (37)______to entanglement in fishing nets, but scientists say they doubt that this alone could (38)_________the recent population decline.

Question 38:

Read the following passage and mark the letter A,B,C or D on your answer sheet to indicate the correct word or phrase that best fits each of the numbered blanks.

A trend that has emerged recently is the sharing of childcare (1) __________ between husband and wife. Young couples will try to arrange their work schedules so that they work opposite hours or shifts in order that one parent is always home with the children. Since childcare is expensive, this saves money for the young couple trying to establish themselves and provide a secure environment for the family. Husband and wife may also share household chores. Some fathers are just as capable as mothers at cooking dinner, changing and bathing the baby, and doing the laundry. In some cases, the woman’s salary is for family (2) __________ and the father becomes the “househusband." These cases are still fairly rare. One positive trend, however, is that fathers seem to be spending more time with their children. In a recent survey, 41% of the children sampled said they spend equal time with their mothers and fathers. “This is one of our most significant cultural changes,” says Dr. Leon Hoffman, who co-directs the Parent Child Center at the New York Psychoanalytic Society. In practice, for over 30 years, Hoffman has found "a very dramatic difference in the involvement of the father in everything from care-taking to general decision (3) __________ around kids' lives.” Another factor has recently been added to the childcare formula. The number of people who work from home nearly full-time rose 23% from the last decade. The (4) _________ of technology - computers, faxes, teleconferencing - has made it easier for at-home workers to be constantly in touch. Will this new flexibility in the workforce bring a positive change for the (5) __________ of children? Only time will tell.  

Question 1:

Read the following passage and mark the letter A,B,C or D on your answer sheet to indicate the correct word or phrase that best fits each of the numbered blanks.

A trend that has emerged recently is the sharing of childcare (1) __________ between husband and wife. Young couples will try to arrange their work schedules so that they work opposite hours or shifts in order that one parent is always home with the children. Since childcare is expensive, this saves money for the young couple trying to establish themselves and provide a secure environment for the family. Husband and wife may also share household chores. Some fathers are just as capable as mothers at cooking dinner, changing and bathing the baby, and doing the laundry. In some cases, the woman’s salary is for family (2) __________ and the father becomes the “househusband." These cases are still fairly rare. One positive trend, however, is that fathers seem to be spending more time with their children. In a recent survey, 41% of the children sampled said they spend equal time with their mothers and fathers. “This is one of our most significant cultural changes,” says Dr. Leon Hoffman, who co-directs the Parent Child Center at the New York Psychoanalytic Society. In practice, for over 30 years, Hoffman has found "a very dramatic difference in the involvement of the father in everything from care-taking to general decision (3) __________ around kids' lives.” Another factor has recently been added to the childcare formula. The number of people who work from home nearly full-time rose 23% from the last decade. The (4) _________ of technology - computers, faxes, teleconferencing - has made it easier for at-home workers to be constantly in touch. Will this new flexibility in the workforce bring a positive change for the (5) __________ of children? Only time will tell.  

Question 2:

Read the following passage and mark the letter A,B,C or D on your answer sheet to indicate the correct word or phrase that best fits each of the numbered blanks.

A trend that has emerged recently is the sharing of childcare (1) __________ between husband and wife. Young couples will try to arrange their work schedules so that they work opposite hours or shifts in order that one parent is always home with the children. Since childcare is expensive, this saves money for the young couple trying to establish themselves and provide a secure environment for the family. Husband and wife may also share household chores. Some fathers are just as capable as mothers at cooking dinner, changing and bathing the baby, and doing the laundry. In some cases, the woman’s salary is for family (2) __________ and the father becomes the “househusband." These cases are still fairly rare. One positive trend, however, is that fathers seem to be spending more time with their children. In a recent survey, 41% of the children sampled said they spend equal time with their mothers and fathers. “This is one of our most significant cultural changes,” says Dr. Leon Hoffman, who co-directs the Parent Child Center at the New York Psychoanalytic Society. In practice, for over 30 years, Hoffman has found "a very dramatic difference in the involvement of the father in everything from care-taking to general decision (3) __________ around kids' lives.” Another factor has recently been added to the childcare formula. The number of people who work from home nearly full-time rose 23% from the last decade. The (4) _________ of technology - computers, faxes, teleconferencing - has made it easier for at-home workers to be constantly in touch. Will this new flexibility in the workforce bring a positive change for the (5) __________ of children? Only time will tell.

Question 3:  

Read the following passage and mark the letter A,B,C or D on your answer sheet to indicate the correct word or phrase that best fits each of the numbered blanks.

A trend that has emerged recently is the sharing of childcare (1) __________ between husband and wife. Young couples will try to arrange their work schedules so that they work opposite hours or shifts in order that one parent is always home with the children. Since childcare is expensive, this saves money for the young couple trying to establish themselves and provide a secure environment for the family. Husband and wife may also share household chores. Some fathers are just as capable as mothers at cooking dinner, changing and bathing the baby, and doing the laundry. In some cases, the woman’s salary is for family (2) __________ and the father becomes the “househusband." These cases are still fairly rare. One positive trend, however, is that fathers seem to be spending more time with their children. In a recent survey, 41% of the children sampled said they spend equal time with their mothers and fathers. “This is one of our most significant cultural changes,” says Dr. Leon Hoffman, who co-directs the Parent Child Center at the New York Psychoanalytic Society. In practice, for over 30 years, Hoffman has found "a very dramatic difference in the involvement of the father in everything from care-taking to general decision (3) __________ around kids' lives.” Another factor has recently been added to the childcare formula. The number of people who work from home nearly full-time rose 23% from the last decade. The (4) _________ of technology - computers, faxes, teleconferencing - has made it easier for at-home workers to be constantly in touch. Will this new flexibility in the workforce bring a positive change for the (5) __________ of children? Only time will tell.  

Question 4:

Read the following passage and mark the letter A,B,C or D on your answer sheet to indicate the correct word or phrase that best fits each of the numbered blanks.

A trend that has emerged recently is the sharing of childcare (1) __________ between husband and wife. Young couples will try to arrange their work schedules so that they work opposite hours or shifts in order that one parent is always home with the children. Since childcare is expensive, this saves money for the young couple trying to establish themselves and provide a secure environment for the family. Husband and wife may also share household chores. Some fathers are just as capable as mothers at cooking dinner, changing and bathing the baby, and doing the laundry. In some cases, the woman’s salary is for family (2) __________ and the father becomes the “househusband." These cases are still fairly rare. One positive trend, however, is that fathers seem to be spending more time with their children. In a recent survey, 41% of the children sampled said they spend equal time with their mothers and fathers. “This is one of our most significant cultural changes,” says Dr. Leon Hoffman, who co-directs the Parent Child Center at the New York Psychoanalytic Society. In practice, for over 30 years, Hoffman has found "a very dramatic difference in the involvement of the father in everything from care-taking to general decision (3) __________ around kids' lives.” Another factor has recently been added to the childcare formula. The number of people who work from home nearly full-time rose 23% from the last decade. The (4) _________ of technology - computers, faxes, teleconferencing - has made it easier for at-home workers to be constantly in touch. Will this new flexibility in the workforce bring a positive change for the (5) __________ of children? Only time will tell.  

Question 5:

Read the following passage and mark the letter A, B, C or D on your answer sheet to indicate the correct word or phrase that best fits each of the numbered blanks from 1 to 5:

Chimpanzees in the wild like to snack on termites, and youngsters learn to fish for them by pocking long sticks and other (1)……tools into the mounds that large groups of termites build. Researchers found that (2)…………average female chimps in the Gombe National Park in Tanzania learnt how to do termite fishing at the age of 31 months, more than two years earlier than the males. The females seem to learn by watching mothers. Researcher Dr. Elisabeth V. Lonsdorf, director of field conservation at the Lincoln Park Zoo in Chicago, said that it is (3)…………to find that, when a young male and female are near a mound, she’s really focusing on termite fishing and he’s spinning himself round (4)………circles. Dr Landsdorf and colleagues are studying chimpanzees at the zoo with a new, specially created termite mound, filled with mustard (5)……than termites. 

 Question 2: