Chất nào sau đây thuộc loại amin bậc I?

A. (CH₃)₃N.

B. CH₃NHCH₃

C. CH₃NH₂

D. CH₃CH₂NHCH₃

Cho X, Y, Z, T là các chất khác nhau trong số 4 chất: CH₃COOH, C₆H₅COOH (axit benzoic), C₂H₅COOH, HCOOH và giá trị nhiệt độ sôi được ghi trong bảng sau:

Nhận xét nào sau đây là đúng ?

A. T là C₆H₅COOH.

B. X là C₂H₅COOH.       

C. Y là CH₃COOH.

D. Z là HCOOH.

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 35 to 42.

Moving Your Mind for Maximum Fitness

  When people design a new workout programme, they often target their chest, stomach, and leg muscles, hoping to sculpt the perfect physique. However, they often neglect the most important part of the body: the brain. Our brains grow stronger when we exercise them and weaker when neglected. To assist in keeping our minds sharp, several websites and apps offer brain games to help us get our mental workouts accomplished in a very short time.

  As we age, our vocabulary continues to expand and we become better at creative plans. However, by the time we enter our 20s, our prefrontal cortex starts to shrink. Although part of the reason for our decline is physical, there is evidence that targeted exercises can halt or even reserve cognitive damage. Throughout our lives we maintain the ability to create new neurons whenever we learn something new, like a foreign language or a new sport. By repeating these activities we create new pathways and connections between neurons that keep our minds functioning at an optimal level. This is what brain fitness exercises aim to accomplish.

  These digital exercises are broken into different categories. The first is memory exercises. These programmes display information to users and then quiz us to see how much we can recall. The second type is attention exercises. These games get users to focus on multiple tasks at once, dividing their attention. Although trying to concentrate on several things at once during work is not recommended, doing it in a game environment can help to strengthen our focus in the long term. Speed exercises, on the other hand, are designed to keep our minds agile. In addition to these major categories, there are other games that focus on specific situations like remembering names and faces, or calculating directions.

  Although many users rave about positive effects of these games, there are other hacks we can use to strengthen our brains. One is napping. Studies have shown that people who nap in the afternoon fared much better at mental tasks than those who didn’t. A little caffeine can also make your mind sharper, as long as you don’t overdo it. Finally, getting some physical exercise also tends to improve the clarity of our thinking. In other words, maybe the Roman poet Juvenal was on to something when he wrote “A sound mind in a healthy body”.

Which of the following statements is NOT true about our brains and brain games?

A. We should concentrate on several things at once during our lives to strengthen our focus. 

B. These brain games don’t take us much time to carry out. 

C. The brain games can help us improve our memory and keep our minds active. 

D. There are some brain games for specific purposes.

Điện phân dung dịch T chứa a gam Cu(NO₃)₂ với điện cực trơ một thời gian rồi nhấc nhanh các điện cực ra thu được dung dịch X. Cho m gam bột Mg vào dung dịch X, sau khi phản ứng xảy ra hoàn toàn thu được 19 gam hỗn hợp kim loại, 0,448 lít hỗn hợp khí Z (đktc) gồm NO và N₂O có tỉ khối đối với H₂ là 18,5 và dung dịch Y chứa 56,3 gam muối. Cho toàn bộ hỗn hợp bột kim loại trên tác dụng với dung dịch HCl dư thu được 1,008 lít khí H₂ (đktc). Giá trị của (m+a) là?

A. 85,28

B. 92,80

C. 78,12

D. 88,42