Phenyl axetat được điều chế trực tiếp từ?  

Phenyl axetat được điều chế trực tiếp từ?  

Khi đun nóng 25,8 gam hỗn hợp gồm ancol etylic và axit axetic có H₂SO₄ đặc làm xúc tác thu được 14.08 gam este. Nếu đốt cháy hoàn toàn hỗn hợp ban đầu đó thu được 23,4 ml nước. Hiệu suất của phản ứng este hóa là ?         

Trong thành phần của dầu gội đầu thường có một số este. Vai trò của các este này là:

Sơ đồ phản ứng nào không đúng?

Este A điều chế từ ancol metyllic có tỷ khối so với oxi là 2,3125. Công thức của A là:

Cho các phát biểu sau:         (1) Phản ứng thủy phân este trong môi trường kiềm là phản ứng thuận nghịch.         (2) Các este của axit fomic đều cho được phản ứng tráng gương.         (3) Trong công nghiệp, lượng lớn chất béo dùng để điều chế xà phòng và chế biến thực phẩm.         (4) Các este có nhiệt độ sôi thấp hơn các axit cacboxylic có cùng số nguyên tử cacbon.  Các phát biểu đúng là.         

Khi đun nóng 25,8 gam hỗn hợp gồm ancol etylic và axit axetic có H2SO4 đặc làm xúc tác thu được 14.08 gam este. Nếu đốt cháy hoàn toàn hỗn hợp ban đầu đó thu được 23,4 ml nước. Hiệu suất của phản ứng este hóa là

Lấy m gam một axit hữu cơ đơn chức X cho tác dụng với NaHCO₃ dư thấy giải phóng 2,2g khí. Mặt khác, cho m gam X vào C₂H₅OH lấy dư trong H₂SO₄ đặc (H = 80%) thì thu được 3,52g este. Giá trị của m là:  

Este X được tạo thành từ etylen glicol và hai axit cacboxylic đơn chức. Trong phân tử este, số nguyên tử cacbon nhiều hơn số nguyên tử oxi là 1. Khi cho m gam X tác dụng với dung dịch NaOH (dư) thì lượng NaOH đã phản ứng là 10 gam. Giá trị của m là:

Đun 12 gam axit axetic với 13,8 gam etanol (có H2SO4 đặc làm xúc tác) đến khi phản ứng đạt tới trạng thái cân bằng, thu được 11 gam este. Hiệu suất của phản ứng este hoá là:  

Read the following passage and mark the letter A, B, C or D on your answer sheet to indicate the correct word for each of the blanks from 46 to 50:

 Here are tips that help succeed in your job interview: Always arrive early. If you do not know (46) _________ the organization is located, call for exact directions (47) ____________ advance. Leave some extra time for any traffic, parking, or unexpected events. If you are running late, call right away and let someone know. The best time to arrive is approximately 5 - 10 minutes early. Give yourself the time to read your resume one more time, to catch your breath, and to be ready for the interview. Once you are at the office, treat everyone you encounter with respect. Be (48) _________ to everyone as soon as you walk in the door. Wear a professional business suit. This point should be emphasized enough. First (49) ____________ are extremely important in the interview process. Women should (50)_________ wearing too much jewelry or make up. Men should avoid flashy suits or wearing too much perfume. It is also important that you feel comfortable. While a suit is the standard interview attire in a business environment, if you think it is an informal environment, call before and ask. Regardless, you can never be overdressed if you are wearing a tailored suit.   

Question 48:

Read the following passage and mark the letter A, B, C or D on your answer sheet to indicate the correct word for each of the blanks from 46 to 50:

 Here are tips that help succeed in your job interview: Always arrive early. If you do not know (46) _________ the organization is located, call for exact directions (47) ____________ advance. Leave some extra time for any traffic, parking, or unexpected events. If you are running late, call right away and let someone know. The best time to arrive is approximately 5 - 10 minutes early. Give yourself the time to read your resume one more time, to catch your breath, and to be ready for the interview. Once you are at the office, treat everyone you encounter with respect. Be (48) _________ to everyone as soon as you walk in the door. Wear a professional business suit. This point should be emphasized enough. First (49) ____________ are extremely important in the interview process. Women should (50)_________ wearing too much jewelry or make up. Men should avoid flashy suits or wearing too much perfume. It is also important that you feel comfortable. While a suit is the standard interview attire in a business environment, if you think it is an informal environment, call before and ask. Regardless, you can never be overdressed if you are wearing a tailored suit.   

Question 47:

Question 34

THOMAS EDISON

On the night of 21 October 1931, millions of Americans took part in a coast-to-coast ceremony to commemorate the passing of a great man. Lights (31) _______ in homes and offices from New York to California. The ceremony marked the death of arguably the most important inventor of all time: Thomas Edison. Few inventors have (32) _______ such an impact on everyday life, and many of his inventions played a crucial role in the development of modern technology. One should never (33) _______ how revolutionary some of Edison’s inventions were. In many ways, Edison is the perfect example of an inventor - that is, not just someone who dreams up clever gadgets, but someone whose products transform the lives of millions. He possessed the key characteristics that an inventor needs to (34) _______ a success of inventions, notably sheer determination. Edison famously tried thousands of materials while working on a new type of battery, reacting to failure by cheerfully announcing to his colleagues: 'Well, (35) _______ we know 8,000 things that don’t work.’ Knowing when to take no notice of experts is also important. Edison’s proposal for electric lighting circuitry was received with total disbelief by eminent scientists, until he lit up whole streets with his lights. .        

Question 35.

THOMAS EDISON

On the night of 21 October 1931, millions of Americans took part in a coast-to-coast ceremony to commemorate the passing of a great man. Lights (31) _______ in homes and offices from New York to California. The ceremony marked the death of arguably the most important inventor of all time: Thomas Edison. Few inventors have (32) _______ such an impact on everyday life, and many of his inventions played a crucial role in the development of modern technology. One should never (33) _______ how revolutionary some of Edison’s inventions were. In many ways, Edison is the perfect example of an inventor - that is, not just someone who dreams up clever gadgets, but someone whose products transform the lives of millions. He possessed the key characteristics that an inventor needs to (34) _______ a success of inventions, notably sheer determination. Edison famously tried thousands of materials while working on a new type of battery, reacting to failure by cheerfully announcing to his colleagues: 'Well, (35) _______ we know 8,000 things that don’t work.’ Knowing when to take no notice of experts is also important. Edison’s proposal for electric lighting circuitry was received with total disbelief by eminent scientists, until he lit up whole streets with his lights.          

Question 32

THOMAS EDISON

On the night of 21 October 1931, millions of Americans took part in a coast-to-coast ceremony to commemorate the passing of a great man. Lights (31) _______ in homes and offices from New York to California. The ceremony marked the death of arguably the most important inventor of all time: Thomas Edison. Few inventors have (32) _______ such an impact on everyday life, and many of his inventions played a crucial role in the development of modern technology. One should never (33) _______ how revolutionary some of Edison’s inventions were. In many ways, Edison is the perfect example of an inventor - that is, not just someone who dreams up clever gadgets, but someone whose products transform the lives of millions. He possessed the key characteristics that an inventor needs to (34) _______ a success of inventions, notably sheer determination. Edison famously tried thousands of materials while working on a new type of battery, reacting to failure by cheerfully announcing to his colleagues: 'Well, (35) _______ we know 8,000 things that don’t work.’ Knowing when to take no notice of experts is also important. Edison’s proposal for electric lighting circuitry was received with total disbelief by eminent scientists, until he lit up whole streets with his lights.   

Question 33.

THOMAS EDISON

On the night of 21 October 1931, millions of Americans took part in a coast-to-coast ceremony to commemorate the passing of a great man. Lights (31) _______ in homes and offices from New York to California. The ceremony marked the death of arguably the most important inventor of all time: Thomas Edison. Few inventors have (32) _______ such an impact on everyday life, and many of his inventions played a crucial role in the development of modern technology. One should never (33) _______ how revolutionary some of Edison’s inventions were. In many ways, Edison is the perfect example of an inventor - that is, not just someone who dreams up clever gadgets, but someone whose products transform the lives of millions. He possessed the key characteristics that an inventor needs to (34) _______ a success of inventions, notably sheer determination. Edison famously tried thousands of materials while working on a new type of battery, reacting to failure by cheerfully announcing to his colleagues: 'Well, (35) _______ we know 8,000 things that don’t work.’ Knowing when to take no notice of experts is also important. Edison’s proposal for electric lighting circuitry was received with total disbelief by eminent scientists, until he lit up whole streets with his lights.          

 Question 31. 

THOMAS EDISON

On the night of 21 October 1931, millions of Americans took part in a coast-to-coast ceremony to commemorate the passing of a great man. Lights (31) _______ in homes and offices from New York to California. The ceremony marked the death of arguably the most important inventor of all time: Thomas Edison. Few inventors have (32) _______ such an impact on everyday life, and many of his inventions played a crucial role in the development of modern technology. One should never (33) _______ how revolutionary some of Edison’s inventions were. In many ways, Edison is the perfect example of an inventor - that is, not just someone who dreams up clever gadgets, but someone whose products transform the lives of millions. He possessed the key characteristics that an inventor needs to (34) _______ a success of inventions, notably sheer determination. Edison famously tried thousands of materials while working on a new type of battery, reacting to failure by cheerfully announcing to his colleagues: 'Well, (35) _______ we know 8,000 things that don’t work.’ Knowing when to take no notice of experts is also important. Edison’s proposal for electric lighting circuitry was received with total disbelief by eminent scientists, until he lit up whole streets with his lights.        

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:

The home was an important aspect of ancient Greek civilization and the term oikos not only meant house or home, but also a man’s domain. (46)_______, home ownership brought with it considerable responsibility, including protection of the home's inhabitants. A typical Athenian (47)_______ in the 5th and 6th centuries BC consisted of a couple, any children might have, plus several slaves. The men were often (48)_______ for work or at war and, as a result, security was a constant worry. A typical dwelling had high walls and a strong gate, and was constructed of mud bricks around a central courtyard, (49)_______ might have been used for cooking, relaxing or socializing with friends and family members. The courtyard also (50)_______ women the chance to enjoy the open air in the privacy of their own home, as they did not normally go out much.

Question 49:

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:

The home was an important aspect of ancient Greek civilization and the term oikos not only meant house or home, but also a man’s domain. (46)_______, home ownership brought with it considerable responsibility, including protection of the home's inhabitants. A typical Athenian (47)_______ in the 5th and 6th centuries BC consisted of a couple, any children might have, plus several slaves. The men were often (48)_______ for work or at war and, as a result, security was a constant worry. A typical dwelling had high walls and a strong gate, and was constructed of mud bricks around a central courtyard, (49)_______ might have been used for cooking, relaxing or socializing with friends and family members. The courtyard also (50)_______ women the chance to enjoy the open air in the privacy of their own home, as they did not normally go out much.

Question 50:

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 31 to 35:

 Nowadays people are more aware that wildlife all over the world is in (31)___________. Many species of animals are threatened, and could easily become (32)___________ if we do not make an effort to protect them. There are many reasons for this. In some cases animals are hunted for their fur or for other valuable parts of their bodies. Some birds, such as parrots, are caught (33)___________, and sold as pets. For many animals and birds, the problem is that their habitats-the place where they live-is disappearing. More land is used for farm, for houses and industry, and there are fewer open spaces than there once were. Farmers use powerful chemicals to help them grow better crops, but these chemicals pollute the environment and (34)___________ wildlife. The most successful animals on Earth, human beings, will soon be the only ones (35)___________ unless we can solve this problem.

Question 32: